Composite ecological device for in-situ enhanced denitrification of low-temperature river water and application

Abstract

The invention relates to a composite ecological device for in-situ enhanced denitrification of a low-temperature river water body and application. The invention discloses a composite ecological device for in-situ enhanced denitrification of a low-temperature river water body. The composite ecological device consists of a thermal insulation layer, a nitrification layer and a denitrification layer which are sequentially arranged from top to bottom, the nitrification layer comprises a biological blanket and a composite biological filler fixed on the biological blanket, and the biological blanket and the composite biological filler are inoculated with low-temperature-resistant nitrifying bacteria; the denitrification layer comprises filler balls, a slow-release carbon source is doped in the filler balls, and low-temperature-resistant denitrifying bacteria are inoculated on the filler balls. The invention also provides application of the in-situ enhanced denitrification composite ecological device for the low-temperature river water body to in-situ denitrification of the low-temperature river water body. The problem that the biological denitrification efficiency of a traditional denitrification process is remarkably reduced in a low-temperature environment is solved, the problems that nitrification products are retained due to unsmooth layering treatment connection and denitrification is inhibited due to insufficient alkalinity of a denitrification area are solved, and the problem that secondary pollution is easily caused due to uncontrollable carbon source addition is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to a composite ecological device for in-situ enhanced denitrification of low-temperature river water bodies and its application. Background Art

[0002] In recent years, the total nitrogen flux of rivers entering the sea has been a key indicator for improving water quality in nearshore waters and has attracted much attention. The dry and low-temperature periods in autumn and winter have become extremely special and critical periods in the protection of the water ecological environment. When the temperature drops suddenly in winter, the ammonia nitrogen and total nitrogen levels will suddenly increase. The main reason is that nitrifying bacteria are more sensitive to water temperature. Nitrifying bacteria are responsible for converting nitrite into nitrate. When the water temperature is lower than the suitable temperature value for nitrifying bacteria, the activity of nitrifying bacteria will be greatly reduced, which will lead to a significant decrease in the degradation rate of ammonia nitrogen. In addition, as the water temperature drops in winter, the activity of microorganisms also decreases, which slows the decomposition of organic matter, which also leads to an increase in ammonia nitrogen and total nitrogen levels.

[0003] However, existing low-temperature water treatment devices are mostly designed for domestic sewage and industrial wastewater treatment. Their frame structures are relatively concentrated and complex, usually tank structures. Most existing equipment is fixed sewage treatment plant facilities and requires power facilities such as heating layers and aeration devices, which makes it impossible to directly apply them to flowing natural water bodies and lacks insulation design.

[0004] At the same time, traditional denitrification processes have the following shortcomings when used in low-temperature natural water bodies: 1) For example, the A / O process relies on microbial activity. When water temperatures fall below 15°C, the activity of nitrifying / denitrifying bacteria drops sharply, with the nitrification rate dropping by 50%-70%. Microbial enzyme activity is also inhibited. For example, the activity of nitrite oxidase at 10°C is only 30% of that at 25°C. 2) Liquid carbon sources (such as methanol and sodium acetate) can easily cause transient overdose, leading to COD fluctuations exceeding 50%. Imbalanced carbon-nitrogen ratios (C / N) can easily trigger the release of N2O greenhouse gases, which can be 3-5 times higher than normal. 3) The heat loss rate of the river environment is high. Without insulation measures, the heat utilization rate of the nitrification reaction is less than 20%. Diurnal temperature fluctuations cause fluctuations in microbial metabolism. When the temperature fluctuates by ±5°C, the stability of denitrification can drop by 40%. 4) Nitrification products (NO 3- ) are not delivered to the denitrification zone in a timely manner, resulting in a retention rate >30%. Furthermore, insufficient alkalinity in the denitrification zone inhibits the denitrification process. For example, when the pH falls below 6.5, denitrifying enzymes become inactive. Therefore, there is an urgent need for an in-situ enhanced denitrification device suitable for low-temperature river waters. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a composite ecological device and application for in-situ enhanced denitrification of low-temperature river water bodies, so as to solve the problem that the biological denitrification efficiency of traditional denitrification processes is significantly reduced under low-temperature environments. It can also solve the problem that the connection between stratified treatment is not smooth, resulting in the retention of nitrification products, and the alkalinity in the denitrification zone is insufficient to inhibit denitrification. It can also solve the problem that uncontrollable carbon source addition can easily lead to secondary pollution, and the problem that it is difficult to maintain thermal energy in open water bodies.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A composite ecological device for in-situ enhanced denitrification of low-temperature river water bodies, comprising a thermal insulation layer, a nitrification layer, and a denitrification layer arranged in sequence from top to bottom; The nitrification layer includes a biological blanket and a composite biological filler fixed on the biological blanket, and the biological blanket and the composite biological filler are inoculated with low-temperature resistant nitrifying bacteria; The denitrification layer includes filler balls, the filler balls are doped with a slow-release carbon source, and the filler balls are inoculated with low-temperature-resistant denitrifying bacteria.

[0007] According to the above technical means, by sequentially arranging the insulation layer, nitrification layer, and denitrification layer from top to bottom, efficient in-situ denitrification of low-temperature river water bodies was achieved. The insulation layer effectively reduced heat loss, maintained the temperature stability of the nitrification and denitrification layers, and provided a suitable living environment for microorganisms. The biological carpet and composite biological filler in the nitrification layer provided abundant attachment surfaces for low-temperature nitrifying bacteria, enabling them to efficiently oxidize ammonia nitrogen to nitrate. The filler balls in the denitrification layer were doped with a slow-release carbon source, providing energy for low-temperature nitrifying bacteria and promoting their reduction of nitrate to nitrogen gas. At the same time, the nitrification layer was arranged above the denitrification layer, so that the heat generated by the nitrification reaction further provided energy to the denitrifying bacteria, further promoting the reduction of nitrate to nitrogen gas. This layered design forms a complete denitrification chain, which not only solves the problem of significantly reduced biological denitrification efficiency in traditional denitrification processes under low-temperature environments, but also solves the problem of poor connection between layered treatments, which leads to retention of nitrification products. At the same time, through the addition of slow-release carbon sources, it avoids the problem of insufficient alkalinity in the denitrification zone inhibiting denitrification, significantly improves the denitrification efficiency, and effectively solves the problem of difficulty in maintaining thermal energy in open water bodies.

[0008] Preferably, the thermal insulation layer comprises an upper light-transmitting thermal insulation cover film and a lower thermal insulation material layer.

[0009] Preferably, the light-transmitting heat-insulating cover film is selected from at least one of a dimming film, a light-to-heat conversion film and a self-cleaning ETFE film.

[0010] Preferably, the material of the thermal insulation material layer is selected from at least one of polyurethane foam thermal insulation material, aerogel felt and phase change energy storage material.

[0011] Preferably, the light transmittance of the dimming film is ≥85%. The dimming film is an electronic light-controlling thin film material made using PDLC (polymer dispersed liquid crystal) technology. Its core characteristic is that it can appear transparent when powered on, and become a translucent but opaque mist when powered off, providing both privacy protection and light regulation functions.

[0012] By selecting a dimming film with a transmittance of ≥85% as the upper material of the insulation layer, it can not only allow sunlight to penetrate efficiently, ensuring that the lower insulation material fully absorbs light energy and heats up, but also effectively play a heat-insulating and protective role for the lower insulation material, significantly reducing its cooling rate.

[0013] Preferably, the thermal conductivity of the polyurethane foam insulation material layer is ≤0.025 W / m·K. Thus, light is used to increase the temperature of the lower nitrification layer and denitrification layer.

[0014] By selecting polyurethane foam insulation materials with a thermal conductivity of ≤0.025 W / m·K, the heat transfer is effectively prevented and the heat loss is reduced, thereby ensuring the water temperature of the nitrification layer and the denitrification layer.

[0015] Preferably, the composite biological filler of the nitrification layer includes composite biological filler balls and biological ropes connecting the composite biological filler balls; The composite biological filler ball is selected from a composite filler ball of volcanic rock and zeolite and / or graphene modified ceramsite, and the specific surface area of ​​the composite filler ball of volcanic rock and zeolite is ≥500 m 2 / m 3 .

[0016] By selecting a specific surface area ≥ 500 m 2 / m 3 The composite filler balls of volcanic rock and zeolite not only ensure the enrichment of low-temperature resistant nitrifying bacteria, but also enhance mass transfer efficiency. The high specific surface area not only provides more microbial attachment sites, but its microporous structure also forms a capillary effect, promoting the diffusion rate of dissolved oxygen and ammonia nitrogen. At the same time, it also buffers pH fluctuations. The CaO in the volcanic rock (content of about 5-8%) and the aluminosilicate structure of the zeolite can neutralize the H generated during the nitrification process. + .

[0017] Preferably, the biological rope is made of a polylactic acid (PLA) braided mesh.

[0018] The composite biological filler balls are connected in series through biological ropes and then fixed on the biological blanket.

[0019] Preferably, the method for preparing the graphene-modified ceramsite comprises the following steps: After the shale ceramsite is acid-washed, graphene is grown on the surface of the shale ceramsite by chemical vapor deposition (CVD) at a temperature of 800°C. The number of graphene layers is 3 to 5.

[0020] Preferably, the composition of the shale ceramsite includes 45-50% aluminum oxide (Al2O3) and 30-35% silicon dioxide (SiO2) by mass percentage, with the remainder being ceramsite.

[0021] Preferably, the pickling is performed by soaking in a 5% nitric acid (HNO3) aqueous solution for 24 hours.

[0022] Preferably, the thickness of the graphene grown on the surface of the shale ceramsite is 1.2-2 nm.

[0023] Preferably, the filler balls of the denitrification layer are selected from composite filler balls of volcanic rock and zeolite and / or metal-organic framework (MOFs) materials, the mass ratio of the volcanic rock to the zeolite is 3:2, the particle size of the composite filler balls of volcanic rock and zeolite is 10-20 mm, and the specific surface area is ≥500 m 2 / m 3 .

[0024] By selecting a particle size of 10~20mm and a specific surface area of ​​≥500 m 2 / m 3 The composite filler balls ensure the efficient enrichment of low-temperature resistant denitrifying bacteria.

[0025] Preferably, the metal-organic framework (MOFs) material is selected from ZIF-8, and the specific surface area of ​​the ZIF-8 is greater than 1000m 2 / m 3 .

[0026] Among them, ZIF-8 (Zeolitic Imidazolate Framework-8) is a metal-organic framework material (MOFs) with unique structure and excellent performance, which belongs to the zeolite imidazolate framework material.

[0027] Preferably, the filler balls of the denitrification layer are doped with composite particles of a slow-release sulfur preparation and a slow-release carbon source, and the C / N ratio of the slow-release carbon source is ≥6.

[0028] By doping the filler balls of the denitrification layer with slow-release sulfur preparations and slow-release carbon source composite particles, the slow-release sulfur preparations act as electron donors (S 0 → SO4 2⁻), synergistically with the slow-release carbon source, provides a stable energy source for the low-temperature-tolerant denitrifying bacteria. This synergistic effect ensures that the low-temperature-tolerant denitrifying bacteria can maintain high denitrification enzyme activity in low-temperature environments, significantly improving in-situ denitrification efficiency under low-temperature conditions and further optimizing the denitrification performance of the entire hybrid ecological device. This effectively solves the problem of uncontrollable carbon source addition, which can easily lead to secondary pollution.

[0029] Preferably, the sustained-release sulfur preparation is selected from sulfur granules and / or sodium thiosulfate-palygorskite sustained-release tablets.

[0030] Preferably, the slow-release carbon source is selected from lignin and / or polyhydroxyalkanoate (PHA).

[0031] Among them, the lignin degradation rate is 0.05-0.1 g / (L·d), which avoids the instantaneous excessive addition of traditional liquid carbon sources (such as methanol) and reduces the risk of carbon emissions. Sulfur oxidation provides electrons (S 0 +6NO3 - →SO4 2- +3N2↑), forming a dual-path denitrification with the lignin carbon source, thereby significantly improving the denitrification rate of low-temperature river water bodies.

[0032] Preferably, the filler balls of the denitrification layer are suspended below the bio-blanket using bio-ropes.

[0033] By using the suspension method, the filler balls of the denitrification layer are directly suspended below the biological blanket, that is, the denitrification layer is directly arranged below the nitrification layer, which effectively ensures that the nitrification products (NO 3- ) is promptly delivered to the denitrification area, which greatly reduces the retention rate and further improves the denitrification efficiency.

[0034] Preferably, the filler balls of the denitrification layer are further loaded with anthraquinone-2-sulfonate (AQS).

[0035] By loading anthraquinone-2-sulfonate (AQS) into the filler balls of the denitrification layer, AQS acts as an electron acceptor during the denitrification process, improving electron transfer efficiency and accelerating the reduction of nitrate (NO⁻) to nitrogen (N₂), thereby increasing denitrification efficiency. Experiments have shown that AQS can significantly increase the denitrification reaction rate and reduce hydraulic retention time.

[0036] Preferably, the low-temperature nitrifying bacteria are selected from immobilized nitrifying bacteria microcapsules and / or magnetic responsive bacterial agents, and the low-temperature nitrifying bacteria are selected from (Arctic isolated strains) and / or cold-resistant Acinetobacter, etc.

[0037] Preferably, the low-temperature resistant denitrifying bacteria is at least one selected from Pseudomonas stutzeri, Thiobacillus and Bacillus.

[0038] Preferably, the bio-blanket is selected from at least one of a polyurethane bio-film blanket, a polyethylene bio-film blanket and a polypropylene bio-film blanket.

[0039] The present invention also provides a composite ecological device for in-situ enhanced denitrification of low-temperature river water as described in the present invention, which is used for in-situ denitrification of low-temperature river water, wherein the temperature of the low-temperature river water is 5-10°C.

[0040] Preferably, the composite ecological device has an in-situ denitrification efficiency of over 50% for low-temperature river water, while the denitrification efficiency of existing denitrification devices is generally around 30%.

[0041] Beneficial effects of the present invention: The composite ecological device for in-situ enhanced denitrification of low-temperature river water bodies of the present invention achieves an efficient in-situ denitrification effect for low-temperature river water bodies by sequentially arranging an insulation layer, a nitrification layer, and a denitrification layer from top to bottom. The insulation layer effectively reduces heat loss, maintains the temperature stability of the nitrification layer and the denitrification layer, and provides a suitable living environment for microorganisms. The biological carpet and composite biological filler in the nitrification layer provide abundant attachment surfaces for low-temperature resistant nitrifying bacteria, enabling them to efficiently oxidize ammonia nitrogen into nitrate; and the filler balls in the denitrification layer are doped with a slow-release carbon source, which provides energy for low-temperature resistant denitrifying bacteria and promotes their reduction of nitrate to nitrogen gas. At the same time, the nitrification layer is arranged above the denitrification layer, so that the heat generated by the exothermic nitrification reaction further provides energy for the denitrifying bacteria, further promoting the reduction of nitrate to nitrogen gas. This layered design forms a complete denitrification chain, which not only solves the problem of significant decline in biological denitrification efficiency in traditional denitrification processes under low-temperature environments, but also solves the problem of poor connection between layered treatments, which leads to the retention of nitrification products. At the same time, through the addition of slow-release carbon sources, the problem of insufficient alkalinity in the denitrification zone inhibiting denitrification is avoided, which significantly improves the denitrification efficiency and effectively solves the problem of difficulty in maintaining heat energy in open water bodies. In addition, the device has a simple structure, is easy to install and maintain, and is suitable for use in natural water bodies such as rivers and lakes. Its eco-friendly characteristics do not require the introduction of chemical agents, meet environmental protection requirements, have significant environmental and economic benefits, and have promotional and application value in the field of low-temperature river water remediation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the structure of the composite ecological device; Figure 2 This is a physical picture of the composite biological filler ball; Figure 3 This is a physical picture of the composite ecological device placed in low-temperature river water to carry out in-situ enhanced nitrogen removal; Among them, 1 is the insulation layer; 2 is the nitrification layer, 21 is the biological blanket, 22 is the composite biological filler ball, 23 is the biological rope; 3 is the denitrification layer, and 31 is the filler ball. DETAILED DESCRIPTION

[0043] 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.

[0044] The purpose of the present invention is to provide a composite ecological device and application for in-situ enhanced denitrification of low-temperature river water bodies, so as to solve the problem that the biological denitrification efficiency of traditional denitrification processes is significantly reduced under low-temperature environments. It can also solve the problem that the layered treatment is not well connected, resulting in the retention of nitrification products, and the alkalinity in the denitrification zone is insufficient to inhibit denitrification. It can also solve the problem that uncontrollable carbon source addition can easily lead to secondary pollution, and the problem that it is difficult to maintain thermal energy in open water bodies.

[0045] Among them, such as Figure 1 As shown, the composite ecological device for in-situ enhanced denitrification of low-temperature river water bodies is composed of an insulation layer 1, a nitrification layer 2, and a denitrification layer 3 arranged in sequence from top to bottom; The nitrification layer 2 includes a biological blanket 21 and a composite biological filler fixed on the biological blanket 21. The biological blanket 21 and the composite biological filler are inoculated with low-temperature resistant nitrifying bacteria. The denitrification layer 3 includes filler balls 31 , which are doped with a slow-release carbon source and inoculated with low-temperature-resistant denitrifying bacteria.

[0046] By sequentially placing the insulation layer, nitrification layer, and denitrification layer from top to bottom, efficient in-situ denitrification of low-temperature river water is achieved. The insulation layer effectively reduces heat loss, maintains stable temperatures in the nitrification and denitrification layers, and provides a suitable living environment for microorganisms. The bio-mat and composite bio-filler in the nitrification layer provide abundant attachment surfaces for cold-resistant nitrifying bacteria, enabling them to efficiently oxidize ammonia nitrogen to nitrate. The filler balls in the denitrification layer, doped with a slow-release carbon source, provide energy for cold-resistant denitrifying bacteria, promoting their reduction of nitrate to nitrogen gas. Placing the nitrification layer above the denitrification layer also allows the heat generated by the nitrification reaction to provide further energy for the denitrifying bacteria, further promoting the reduction of nitrate to nitrogen gas. This layered design forms a complete denitrification chain, which not only solves the problem of significantly reduced biological denitrification efficiency in traditional denitrification processes under low-temperature environments, but also solves the problem of poor connection between layered treatments, which leads to retention of nitrification products. At the same time, through the addition of slow-release carbon sources, it avoids the problem of insufficient alkalinity in the denitrification zone inhibiting denitrification, significantly improves the denitrification efficiency, and effectively solves the problem of difficulty in maintaining thermal energy in open water bodies.

[0047] Among them, the nitrification reaction in the upper nitrification layer 2 releases about 4.3 kcal of heat per 1 g of NH3-N oxidized, thereby providing slow and continuous energy for the low-temperature resistant denitrifying bacteria in the lower layer.

[0048] In some embodiments, in order to allow sunlight to penetrate efficiently, ensure that the lower layer of insulation material fully absorbs light energy and heats up, and effectively play a heat-insulating and protective role on the lower layer of insulation material, significantly reducing its cooling rate, the insulation layer is set to include an upper layer of translucent insulation cover film and a lower layer of insulation material layer.

[0049] Energy-saving insulation is achieved through the ingenious placement of a translucent, heat-insulating film and a layer of insulation material to store solar heat. Tests have shown that the physical insulation provided by the translucent, heat-insulating film and insulation material layers maintains the temperature of the nitrification layer 2 and the denitrification layer 3 at 8-12°C. The optimal temperature for the cryoresistant bacterial agent is 8-15°C, ensuring that the enzyme activity of the cryoresistant bacterial agent remains above 70%, while the enzyme activity of traditional mesophilic bacteria at this temperature is less than 30%.

[0050] In some embodiments, the light-transmitting heat-insulating cover film is selected from at least one of a dimming film, a light-to-heat conversion film, and a self-cleaning ETFE film.

[0051] The light-to-heat conversion film contains a nano-indium tin oxide coating, which can further convert 30% of light energy into heat energy. The self-cleaning ETFE film is coated with titanium dioxide, reducing the light transmission loss rate to less than 5% per year.

[0052] In some embodiments, the material of the thermal insulation layer is selected from at least one of polyurethane foam thermal insulation material, aerogel felt and phase change energy storage material.

[0053] The thermal conductivity of the aerogel felt is ≤0.018 W / m·K. The phase change energy storage material is a paraffin / expanded graphite composite with a phase change temperature of 10-15°C.

[0054] In some embodiments, the light transmittance of the dimming film is ≥85%. The dimming film is an electronic light-controlling thin film material made using PDLC (polymer dispersed liquid crystal) technology. Its core characteristic is that it can appear transparent when powered on and become a translucent but opaque mist when powered off, providing both privacy protection and light regulation functions.

[0055] In some embodiments, to effectively prevent heat transfer and reduce heat loss, thereby ensuring the water temperature in the nitrification and denitrification layers, a polyurethane foam insulation material with a thermal conductivity of ≤0.025 W / m·K is selected as the insulation material layer. Light is then used to raise the temperature of the lower nitrification and denitrification layers.

[0056] In some embodiments, the composite biological filler of the nitrification layer 2 includes composite biological filler balls 22 and biological ropes 23 connecting the composite biological filler balls 22; Among them, such as Figure 2 As shown, the composite biological filler ball 22 is selected from a composite filler ball of volcanic rock and zeolite and / or graphene modified ceramsite, and the specific surface area of ​​the composite filler ball of volcanic rock and zeolite is ≥500 m 2 / m 3 .

[0057] In some embodiments, the bio-ropes 23 are made of a polylactic acid (PLA) woven mesh. The composite biofiller balls 22 are connected in series via the bio-ropes 23 and then secured to the bio-blanket 21. The PLA woven mesh is biodegradable and has a surface area 20% greater than that of typical bio-ropes.

[0058] In some embodiments, a method for preparing graphene-modified ceramsite comprises the following steps: After the shale ceramsite is acid-washed, graphene is grown on the surface of the shale ceramsite by chemical vapor deposition (CVD) at a temperature of 800°C. The number of graphene layers is 3 to 5.

[0059] The shale ceramsite is composed of 45-50% aluminum oxide (Al2O3) and 30-35% silicon dioxide (SiO2) by mass. Acid washing involves immersing the ceramsite in a 5% nitric acid (HNO3) aqueous solution for 24 hours. The graphene grown on the shale ceramsite has a thickness of 1.2-2 nm.

[0060] Graphene-modified expanded clay makes it conductive. Tests have shown that this conductivity improves the activity of nitrifying bacteria by about 30%.

[0061] When graphene-modified ceramsite is used as composite biofiller balls, the reaction mechanism is as follows: 1) Reconstruction of electron transfer path: Graphene's sp² hybrid orbitals form continuous electron transport channels, and nitrifying bacteria (Nitrosomonas) directly transfer electrons (e⁻) produced by ammonia oxidation to the conductive carrier via cytochrome c (Cyt c): NH3 → NH2OH → NO2⁻ (releases 4e⁻) The increased conductivity increases the electron transfer rate from 0.3 e⁻ / s / cell of traditional carriers to 1.2 e⁻ / s / cell (a four-fold increase).

[0062] 2) Regulation of biofilm metabolism: The conductive ceramsite surface generates a microelectric field (approximately 0.15 V / m), which promotes the adjustment of the polysaccharide (PS) to protein (PN) ratio in EPS (extracellular polymeric substances) from 1:1.2 to 1:0.8, enhancing the mechanical strength of the biofilm (shear resistance increased by 65%). Microcurrent stimulation also increases ammonia monooxygenase (AMO) activity from 0.8 U / mg to 1.2 U / mg (+50%). A comparison of the metabolic kinetics with conventional ceramsite (untreated or unmodified ceramsite) is shown in Table 1.

[0063] Table 1 shows the comparison of metabolic kinetics In some embodiments, the filler balls of the denitrification layer are selected from composite filler balls of volcanic rock and zeolite and / or metal-organic framework (MOFs) materials, wherein the particle size of the composite filler balls of volcanic rock and zeolite is 10-20 mm, and the specific surface area is ≥500 m 2 / m 3 .

[0064] By selecting a particle size of 10~20mm and a specific surface area of ​​≥500 m 2 / m 3 The composite filler balls ensure the efficient enrichment of low-temperature resistant denitrifying bacteria.

[0065] In some embodiments, the metal-organic framework (MOFs) material is selected from ZIF-8, wherein the specific surface area of ​​the ZIF-8 is greater than 1000 m 2 / m 3 Among them, ZIF-8 (Zeolitic Imidazolate Framework-8) is a metal-organic framework material (MOFs) with unique structure and excellent performance, belonging to the zeolitic imidazolate framework material.

[0066] In some embodiments, the filler balls 31 of the denitrification layer 3 are doped with slow-release sulfur preparations and slow-release carbon source composite particles, and the C / N ratio of the slow-release carbon source is ≥ 6. The slow-release sulfur preparation acts as an electron donor (S 0 → SO4 2 ⁻), synergistically with the slow-release carbon source, provides a stable energy source for the low-temperature-tolerant denitrifying bacteria. This synergistic effect ensures that the low-temperature-tolerant denitrifying bacteria can maintain high denitrification enzyme activity in low-temperature environments, significantly improving in-situ denitrification efficiency under low-temperature conditions and further optimizing the denitrification performance of the entire hybrid ecological device. This effectively solves the problem of uncontrollable carbon source addition, which can easily lead to secondary pollution.

[0067] In some embodiments, the filler balls 31 of the denitrification layer 3 are suspended below the bio-blanket using bio-ropes 23 .

[0068] In some embodiments, the sustained-release sulfur formulation is selected from sulfur granules and / or sodium thiosulfate-palygorskite sustained-release tablets. Experimental results show that using sulfur granules instead of traditional carbon sources (such as methanol) reduces CO2 emissions by 0.8 kg per ton of water treated. Furthermore, the sustained-release period of sulfur granules and sodium thiosulfate-palygorskite sustained-release tablets is as long as 60 days.

[0069] In some embodiments, the slow-release carbon source is selected from lignin and / or polyhydroxyalkanoate (PHA) particles. The degradation rate of lignin is 0.05-0.1 g / (L·d), which avoids the instantaneous over-dosage of traditional liquid carbon sources (such as methanol) and reduces the risk of carbon emissions. Sulfur oxidation provides electrons (S 0 +6NO3 - →SO4 2- +3N2↑), forming a dual-path denitrification with the lignin carbon source, thereby significantly improving the denitrification rate of low-temperature river water bodies.

[0070] Among them, the C / N ratio of polyhydroxyalkanoate (PHA) particles is 8:1, and their biodegradation is controllable.

[0071] In some embodiments, the filler balls in the denitrification layer are also loaded with anthraquinone-2-sulfonate (AQS). By loading the filler balls with anthraquinone-2-sulfonate (AQS), AQS can act as an electron acceptor during the denitrification process, improving electron transfer efficiency and accelerating the reduction of nitrate (NO⁻) to nitrogen gas (N₂), thereby enhancing denitrification efficiency. Experiments have shown that AQS can significantly increase the denitrification reaction rate and reduce hydraulic retention time.

[0072] In some embodiments, the low-temperature resistant nitrifying bacteria are selected from immobilized nitrifying bacteria microcapsules and / or magnetically responsive bacterial agents.

[0073] Among them, the carrier of the immobilized nitrifying bacteria microcapsules is a sodium alginate-attapulgite composite carrier, which can ensure that the survival rate of nitrifying bacteria at low temperatures is >80%.

[0074] The magnetically responsive bacterial agent loads bacteria through Fe3O4 and can regulate the distribution of biofilm through magnetic field.

[0075] Among them, the low-temperature nitrifying bacteria are selected from (Arctic isolated strains) and / or cold-resistant Acinetobacter, etc.

[0076] In some embodiments, the low-temperature tolerant denitrifying bacteria is selected from at least one of Pseudomonas stutzeri, Thiobacillus and Bacillus.

[0077] In some embodiments, the bio-mat is selected from at least one of a polyurethane bio-film mat, a polyethylene bio-film mat, and a polypropylene bio-film mat.

[0078] In some embodiments, a composite ecological device for in-situ enhanced denitrification of low-temperature river water is provided for in-situ denitrification of low-temperature river water, wherein the temperature of the low-temperature river water is 5-10°C. The composite ecological device has an efficiency of over 50% for in-situ denitrification of low-temperature river water.

[0079] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer, the composite ecological device and application of the in-situ enhanced denitrification of low-temperature 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 the embodiments. 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.

[0080] 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.

[0081] Example 1 A composite ecological device for in-situ enhanced denitrification of low-temperature river water bodies is used for a method for in-situ enhanced denitrification of low-temperature river water bodies, comprising the following steps: S1. Preparation of a composite ecological device for in-situ enhanced denitrification of low-temperature river water: The composite ecological device consists of an insulation layer, a nitrification layer, and a denitrification layer arranged in sequence from top to bottom; The insulation layer includes a dimming film with a light transmittance of ≥85% on the upper layer and a polyurethane foam insulation material with a thermal conductivity of ≤0.025 W / m·K on the lower layer; The nitrification layer includes a polyurethane biofilm blanket and graphene-modified ceramsite balls fixed on the polyurethane biofilm blanket, and the polyurethane biofilm blanket and the graphene-modified ceramsite balls are inoculated with immobilized nitrifying bacteria microcapsules; Graphene-modified ceramsite balls were connected in series through a polylactic acid (PLA) woven mesh and then fixed on a polyurethane biofilm blanket. Both the graphene-modified ceramsite balls and the polyurethane biofilm blanket were inoculated with nitrifying bacteria, including at least Candida nitroso (an Arctic isolate) and psychrophilic Acinetobacter. The preparation method of graphene-modified ceramsite balls is as follows: shale ceramsite containing 50% aluminum oxide (Al2O3) and 35% silicon dioxide (SiO2) by mass is soaked in a 5% nitric acid (HNO3) aqueous solution for 24 hours, and then graphene is grown on the surface of the shale ceramsite by chemical vapor deposition (CVD) at a temperature of 800°C. The number of graphene layers is 5. The thickness of the graphene grown on the shale ceramsite surface is 2nm. The denitrification layer includes particles with a diameter of 10-20 mm and a specific surface area of ​​≥500 m 2 / m 3 The composite filler balls are composed of composite filler balls with a mass ratio of volcanic rock to zeolite of 3:2. The composite filler balls are suspended on a polyurethane biofilm blanket through a polylactic acid (PLA) woven mesh. The composite filler balls are doped with sulfur particles and lignin slow-release carbon source (C / N ≥ 6). The composite filler balls are inoculated with low-temperature resistant denitrifying bacteria, wherein the denitrifying bacteria include at least Pseudomonas stutzeri, Thiobacillus and Bacillus.

[0082] The structural diagram of the composite ecological device is as follows: Figure 1 As shown; S2, filling filler: such as Figure 3 As shown in Figure 1, the composite ecological device prepared in S1 was placed in the farmland drainage area of ​​Rudong County, Nantong City, Jiangsu Province. The continuous water body has low mobility and the water flow rate is ≤1 m 3 / s, low temperature environment (around 5℃), river water volume to be treated: 12 m wide × 20 m long × 1 m deep = 240 m 3 The dimensions of the composite ecological device were set to the same level based on the river flow and channel dimensions. On the first day, the composite ecological device was deployed in the river test area. Starting from the second day, water samples were collected daily at 5:00 PM from 300 m upstream and directly below the composite ecological device to measure total nitrogen, nitrate nitrogen, and ammonia nitrogen. The experiment lasted for eight days, and total nitrogen, nitrate nitrogen, and ammonia nitrogen in the water samples were measured by a third-party professional testing company. The results are shown in Table 2.

[0083] Table 2 Determination results of total nitrogen, nitrate nitrogen and ammonia nitrogen Table 2 shows the trends in total nitrogen, nitrate nitrogen, and ammonia nitrogen upstream and at the device, as analyzed based on the available monitoring data. Before the device was deployed, the total nitrogen concentration in the test area was 1.49 mg / L. 48 hours after deployment, the total nitrogen concentration at the device decreased to 1.15 mg / L, representing a removal efficiency of approximately 23%. Over the course of the seven-day trial, the test area achieved a sustained and stable overall reduction in total nitrogen, achieving an overall total nitrogen removal efficiency of approximately 51%, with the total nitrogen concentration dropping from 1.49 mg / L to 0.73 mg / L.

[0084] In summary, the composite ecological device for in-situ enhanced denitrification of low-temperature river water bodies of the present invention achieves an efficient in-situ denitrification effect for low-temperature river water bodies by sequentially arranging an insulation layer, a nitrification layer, and a denitrification layer from top to bottom. The insulation layer effectively reduces heat loss, maintains the temperature stability of the nitrification layer and the denitrification layer, and provides a suitable living environment for microorganisms. The biological carpet and composite biological filler in the nitrification layer provide abundant attachment surfaces for low-temperature resistant nitrifying bacteria, enabling them to efficiently oxidize ammonia nitrogen into nitrate; and the filler balls in the denitrification layer are doped with a slow-release carbon source, which provides energy for low-temperature resistant denitrifying bacteria and promotes their reduction of nitrate to nitrogen gas. At the same time, the nitrification layer is arranged above the denitrification layer, so that the heat generated by the exothermic nitrification reaction further provides energy for the denitrifying bacteria, further promoting the reduction of nitrate to nitrogen gas. This layered design forms a complete denitrification chain, which not only solves the problem of significant decline in biological denitrification efficiency in traditional denitrification processes under low-temperature environments, but also solves the problem of poor connection between layered treatments, which leads to the retention of nitrification products. At the same time, through the addition of slow-release carbon sources, the problem of insufficient alkalinity in the denitrification zone inhibiting denitrification is avoided, which significantly improves the denitrification efficiency and effectively solves the problem of difficulty in maintaining heat energy in open water bodies. In addition, the device has a simple structure, is easy to install and maintain, and is suitable for use in natural water bodies such as rivers and lakes. Its eco-friendly characteristics do not require the introduction of chemical agents, meet environmental protection requirements, have significant environmental and economic benefits, and have promotional and application value in the field of low-temperature river water remediation technology.

[0085] 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 device for in-situ enhanced denitrification of low-temperature river water, characterized in that: It consists of an insulation layer, a nitrification layer and a denitrification layer arranged in sequence from top to bottom; The nitrification layer includes a biological blanket and a composite biological filler fixed on the biological blanket, and the biological blanket and the composite biological filler are inoculated with low-temperature resistant nitrifying bacteria; The denitrification layer includes filler balls, the filler balls are doped with a slow-release carbon source, and the filler balls are inoculated with low-temperature-resistant denitrifying bacteria.

2. The composite ecological device for in-situ enhanced denitrification of low-temperature river water according to claim 1, characterized in that: The heat-insulating layer comprises an upper light-transmitting heat-insulating cover film and a lower heat-insulating material layer.

3. The composite ecological device for in-situ enhanced denitrification of low-temperature river water according to claim 2, characterized in that: The light-transmitting heat-insulating cover film is selected from at least one of a dimming film, a light-to-heat conversion film and a self-cleaning ETFE film; And / or, the material of the thermal insulation material layer is selected from at least one of polyurethane foam thermal insulation material, aerogel felt and phase change energy storage material.

4. The composite ecological device for in-situ enhanced denitrification of low-temperature river water according to claim 1, characterized in that: The composite biological filler of the nitrification layer includes composite biological filler balls and biological ropes connecting the composite biological filler balls; The composite biological filler ball is selected from a composite filler ball of volcanic rock and zeolite and / or graphene modified ceramsite, and the specific surface area of ​​the composite filler ball of volcanic rock and zeolite is ≥500 m 2 / m 3 , the mass ratio of the volcanic rock to the zeolite is 3:2; And / or, the biological rope is made of a polylactic acid (PLA) braided mesh.

5. The composite ecological device for in-situ enhanced denitrification of low-temperature river water according to claim 4, characterized in that: The preparation method of the graphene-modified ceramsite comprises the following steps: After the shale ceramsite is acid-washed, graphene is grown on the surface of the shale ceramsite by chemical vapor deposition (CVD) at a temperature of 800°C. The number of graphene layers is 3 to 5.

6. The composite ecological device for in-situ enhanced denitrification of low-temperature river water according to claim 1, characterized in that: The filler balls of the denitrification layer are selected from composite filler balls of volcanic rock and zeolite and / or metal-organic framework (MOFs) materials. The particle size of the composite filler balls of volcanic rock and zeolite is 10-20 mm, and the specific surface area is ≥500 m 2 / m 3 .

7. The composite ecological device for in-situ enhanced denitrification of low-temperature river water according to claim 1, characterized in that: The filler balls of the denitrification layer are doped with slow-release sulfur preparation and slow-release carbon source composite particles, and the C / N ratio of the slow-release carbon source is ≥6; And / or, the filler balls of the denitrification layer are suspended below the bio-blanket by using bio-ropes.

8. The composite ecological device for in-situ enhanced denitrification of low-temperature river water according to claim 7, characterized in that: The sustained-release sulfur preparation is selected from sulfur granules and / or sodium thiosulfate-palygorskite sustained-release tablets; And / or, the slow-release carbon source is selected from lignin and / or polyhydroxyalkanoate (PHA).

9. The composite ecological device for in-situ enhanced denitrification of low-temperature river water according to claim 1, characterized in that: The filler balls of the denitrification layer are also loaded with anthraquinone-2-sulfonate (AQS); And / or, the low-temperature nitrifying bacteria are selected from immobilized nitrifying bacteria microcapsules and / or magnetic responsive bacterial agents, and the low-temperature nitrifying bacteria are selected from nitroso Candida and / or psychrophilic Acinetobacter; And / or, the low-temperature resistant denitrifying bacteria is selected from at least one of Pseudomonas stutzeri, Thiobacillus and Bacillus; And / or, the bio-blanket is selected from at least one of a polyurethane bio-film blanket, a polyethylene bio-film blanket and a polypropylene bio-film blanket.

10. An application of the composite ecological device for in-situ enhanced denitrification of low-temperature river water bodies according to any one of claims 1 to 9, characterized in that: The composite ecological device is used for in-situ denitrification of low-temperature river water, wherein the temperature of the low-temperature river water is 5-10°C; The efficiency of the composite ecological device in carrying out in-situ denitrification on low-temperature river water bodies is above 50%.

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