Ammonia direct oxidation denitrification device for water body remediation and composite microbial carrier

Abstract

The invention discloses an ammonia direct oxidation denitrification device for water body remediation and a composite microbial carrier. The composite microbial carrier comprises an acetone slow-release inner core and a biological load shell, the acetone slow-release inner core is composed of an acetone-loaded solid adsorbent core and a calcium alginate gel wrapping layer, and precise and long-acting slow release of acetone is achieved through cooperation of adsorption immobilization and a gel diffusion barrier; the biological load shell is composed of polyurethane foam with a three-dimensional communicated macroporous structure, the inner core is wrapped in the shell, and the shell provides a three-dimensional space for microorganism attachment growth and AMAO reaction and delays outward diffusion of acetone. The device comprises a modular remediation unit assembled by a plurality of composite microbial carriers, the modular remediation unit is added into the ammonia nitrogen polluted water body, ammonia nitrogen in the water body is directly oxidized into nitrogen by the AMAO functional flora, and in-situ continuous denitrification is realized. The method solves the problems that the carbon source is easy to diffuse and lose and microorganisms are difficult to colonize, and has the advantages of high remediation efficiency, lasting effect and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering and water pollution bioremediation technology, specifically relating to a direct ammonia oxidation denitrification device and a composite microbial carrier for water remediation. Background Technology

[0002] Lakes, reservoirs, urban landscape water bodies, and some slow-flowing rivers generally face ammonia nitrogen pollution problems, leading to eutrophication, black and odorous water bodies, and ecological degradation. Traditional in-situ remediation technologies have some drawbacks: (1) They rely on aeration and reoxygenation, which can promote nitrification and convert ammonia nitrogen into nitrates, but cannot achieve total nitrogen removal and may even aggravate nitrate nitrogen pollution. (2) Adding microbial agents: the bacteria are easily lost in the water and difficult to colonize, and the effect is short-lived and unstable. (3) Adding carbon sources (such as sodium acetate and glucose) to enhance denitrification, the carbon sources diffuse and dilute rapidly in the water, and the utilization rate is extremely low; excessive carbon sources may lead to a secondary increase in COD in the water body, causing an explosive growth of heterotrophic bacteria and disrupting the ecological balance. (4) Constructing artificial wetlands or ecological floating beds, which rely on plant absorption and microbial action, the nitrogen removal efficiency is greatly affected by the season and plant growth cycle, and the area occupied is large.

[0003] Recent studies have confirmed a novel microbial pathway hidden in nature that can directly oxidize ammonia into nitrogen gas—acetone-mediated ammonium oxidation (AMAO, acetone + ammonia → acetone oxime → acetone + nitrogen gas). Compared with traditional denitrification processes such as nitrification-denitrification, the potential advantages of applying this pathway to the remediation of ammonia-contaminated water bodies are: (1) Directly oxidizing ammonia into nitrogen gas avoids intermediate nitrogen accumulation, resulting in a high total nitrogen removal rate, while the dissolved oxygen requirement is more than half that of nitrification; (2) No need to add denitrification carbon source, acetone can be recycled by microorganisms as a reaction mediator rather than a consumed substrate, resulting in high carbon source utilization; (3) AMAO microorganisms are widely distributed, easy to enrich and cultivate, have flexible metabolic modes (aerobic / anoxic, autotrophic / heterotrophic), and are highly resistant to load shocks, which provides a solid biological basis for constructing a stable and reliable in-situ remediation system. The discovery and utilization of the AMAO pathway offers a revolutionary technological path to address common challenges in current ammonia nitrogen pollution control, such as efficiency bottlenecks, high costs, and secondary pollution. However, this pathway remains in the laboratory research stage and has not yet been specifically applied or engineered in actual water remediation. There is a lack of practical technical solutions and devices for stabilizing and immobilizing AMAO functional microbial communities, precisely and sustainably supplying acetone as a carbon source to the microbial reaction zone, and spatially coupling the slow release of carbon sources with microbial metabolism. This makes it difficult to translate its advantages into actual remediation effectiveness. Summary of the Invention

[0004] In view of this, the purpose of this invention is to solve the problem of how to apply the newly discovered acetone-mediated ammonia oxidation pathway to actual water body remediation, and to provide an ammonia direct oxidation denitrification device and a composite microbial carrier for water body remediation.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A composite microbial carrier for direct ammonia oxidation and denitrification in water remediation, comprising an acetone-releasing core and a bioload shell; The acetone slow-release core includes a solid adsorbent as the core and a calcium alginate gel layer coated on the core, and acetone is loaded on the solid adsorbent. The slow release of acetone is achieved through the acetone slow-release core. The bioburden shell is made of polyurethane foam with a three-dimensional interconnected macroporous structure, and the acetone-releasing core is encapsulated inside the polyurethane foam. The bioburden shell is used to immobilize acetone-mediated ammonia oxidation functional bacteria, provide a three-dimensional space for microbial attachment, growth and AMAO reaction, and delay the diffusion of acetone to the outside of the bioburden shell.

[0006] Furthermore, the acetone loaded on the solid adsorbent exists in the acetone slow-release core in an adsorbed state, forming a first diffusion barrier through the hydrophilic network of the calcium alginate gel layer. The solid adsorbent's retention of acetone provides a secondary slow release.

[0007] Furthermore, the solid adsorbent is activated carbon.

[0008] Furthermore, the preparation method of the acetone sustained-release core is as follows: S1. Weigh the set amount of pretreated activated carbon powder, immerse it in an acetone aqueous solution with a volume concentration not exceeding 50%, and shake to adsorb until saturation. S2. Filter to obtain wet activated carbon loaded with acetone; S3. Dissolve sodium alginate in deionized water to prepare a 2%~4% (w / v) solution; S4. Mix the wet activated carbon in S2 with the sodium alginate solution prepared in S3 at a mass ratio of 0.5~1:2~3, stir evenly to form a composite slurry; S5. The slurry is dropped dropwise into a 4% (w / v) calcium chloride solution. After the droplets come into contact with the calcium solution, their surfaces quickly cross-link into spheres. S6. After solidification, the product is removed and rinsed with deionized water to obtain wet calcium alginate-activated carbon composite gel microspheres, which are acetone-release cores.

[0009] Furthermore, the diameter of the core is 0.5~2cm; the pore size of the polyurethane foam is 1~4mm.

[0010] Furthermore, the three-dimensional interconnected macroporous structure of the bio-load shell is prepared by particle leaching, and the water-soluble porogen used has a particle size of 1~4 mm.

[0011] Furthermore, the method for preparing the bio-load shell is as follows: S1. Weigh out sodium chloride crystals of a set particle size as a water-soluble pore-forming agent and fill them into a cylindrical mold. S2. Mix the polyether-type polyurethane prepolymer with the foaming agent, catalyst and deionized water in a certain proportion, and pour it into the mold so that the prepolymer is immersed in and surrounds the pore-forming agent particles. S3. Curing at 60°C, immersing the cured polyurethane block in deionized water, changing the water regularly until no chloride ions are detected in the water, so as to completely remove sodium chloride crystals by leaching, thereby forming a three-dimensional interconnected macroporous network in the polyurethane. S4. Cut the obtained porous polyurethane material into the desired shape, leaving a cavity in the center for inserting the acetone slow-release core.

[0012] A direct ammonia oxidation denitrification device for water body remediation includes one or more composite microbial carriers as described above, and a physical structural frame for supporting and fixing the composite microbial carriers; the physical structural frame is a bio-rope, bio-cage, floating bio-bed, or submerged bio-grid; the three-dimensional interconnected macroporous structure of the bio-load shell is immobilized with acetone-mediated ammonia oxidation functional bacteria, which use low-concentration acetone diffused from the acetone slow-release core as a circulation mediator to directly oxidize ammonia nitrogen diffused into the bio-load shell from the water body into nitrogen gas.

[0013] Furthermore, the composite microbial carrier is spaced out and loaded onto the physical structural framework.

[0014] The beneficial effects of this invention are as follows: 1. Precise and controllable sustained release of acetone: This invention adopts a dual sustained release mechanism of "adsorbent + gel" to overcome the technical difficulties of direct encapsulation of liquid acetone, and achieves stable release of acetone at ultra-low concentrations (such as 0.1~5mg / L) and for ultra-long periods (2-3 months), fundamentally avoiding the instantaneous release and loss of acetone.

[0015] 2. Stable microbial ecosystem: The macroporous polyurethane shell of the composite microbial carrier in this invention provides microorganisms with a protected three-dimensional growth space similar to a natural habitat, resulting in high microbial density, strong activity, significantly improved resistance to environmental shocks, and less susceptibility to loss.

[0016] 3. Long-lasting and efficient repair efficacy: The structural design of the core and outer network in the composite microbial carrier allows for a tight spatial coupling between acetone supply and microbial metabolism, forming a highly efficient "microreactor". At the same time, the use of a mesh-like porous polyurethane with a certain acetone adsorption capacity as the outer shell can enhance the residence time of acetone at the AMAO bacteria aggregation site, and the slow-release core continuously releases low concentrations of acetone, providing the necessary carbon source for the high-density fixed AMAO functional bacteria in the outer shell, resulting in high denitrification efficiency and a long action cycle.

[0017] 4. Good environmental compatibility and safety: All materials used in this invention (sodium alginate, polyurethane, activated carbon) are environmentally friendly; the acetone release concentration is low and it is utilized in situ, with no risk of secondary pollution.

[0018] In summary, this invention achieves a fixed-point, long-term supply of carbon sources and stable enrichment of functional microorganisms, solving the problems of easy carbon source diffusion and loss and difficulty in microbial colonization in traditional technologies. It has the advantages of high remediation efficiency, long-lasting effect, and environmental friendliness.

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the composite microbial carrier for direct ammonia oxidation and denitrification used in water remediation in this invention.

[0021] Figure 2 Acetone slow-release curve of the composite microbial carrier in actual remediation in this invention.

[0022] Figure 3 This is a schematic diagram of the repair module formed by biological rope and composite microbial carrier in this invention.

[0023] Figure 4 This is a schematic diagram of the repair module formed by the biological cage and the composite microbial carrier in this invention.

[0024] Figure 5 This is a schematic diagram of the repair module formed by the floating bed and composite microbial carrier in this invention.

[0025] Figure 6 This is a graph showing the change of ammonia nitrogen concentration upstream and downstream of the device over time when a biological cage-type restoration module is used to restore a landscape water body in Embodiment 2 of the present invention. Detailed Implementation

[0026] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0027] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0028] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0029] Example 1 Please see Figure 1 This embodiment provides a composite microbial carrier for direct ammonia oxidation and denitrification in water remediation, comprising: a) Acetone sustained-release core: It consists of a solid adsorbent loaded with acetone as the core, and is coated with a calcium alginate gel layer; the diameter of the acetone sustained-release core is 0.5~2cm. b) Bioburden shell: It is made of polyurethane foam with a three-dimensional interconnected macroporous structure, and the acetone slow-release core is encapsulated inside the polyurethane foam; the pore size of the polyurethane foam is 1~4mm, which is used to immobilize acetone-mediated ammonia oxidation functional bacteria.

[0030] In this process, the acetone loaded on the solid adsorbent exists in the acetone slow-release core in an adsorbed state. The first diffusion barrier is formed through the hydrophilic network of the calcium alginate gel layer, and the retention effect of the solid adsorbent on the acetone provides a secondary slow release.

[0031] The acetone-releasing core of this invention consists of a solid adsorbent core and a calcium alginate gel coating layer. First, an aqueous acetone solution is loaded onto activated carbon with a high specific surface area to form a stable "acetone library." Then, the loaded adsorbent, or a slurry using it as a filler, is encapsulated and solidified with calcium alginate gel. The hydrophilic network of the calcium alginate gel forms the first diffusion barrier, while the adsorbent's retention of acetone provides a secondary slow release; the two work synergistically to achieve an ultra-slow release of acetone from several weeks to several months. The release rate can be precisely controlled by adjusting the activated carbon loading, gel concentration, and degree of cross-linking. The preparation method of this acetone-releasing core is as follows: S1. Weigh a certain amount of pretreated activated carbon powder (200 mesh), immerse it in an acetone aqueous solution with a volume concentration of 50%, and shake to adsorb for 12 hours until saturation.

[0032] S2. Filter to obtain wet activated carbon loaded with acetone.

[0033] S3. Dissolve sodium alginate in deionized water to prepare a 3% (w / v) solution.

[0034] S4. Mix the above wet activated carbon with sodium alginate solution at a mass ratio of 0.5~1:2~3, stir evenly to form a composite slurry.

[0035] S5. Using a syringe, dropwise add the slurry into a 4% (w / v) calcium chloride solution. Upon contact with the calcium solution, the droplets rapidly cross-link and form spheres. S6. After curing for 30 minutes, remove the product and rinse it lightly with deionized water to obtain wet calcium alginate-activated carbon composite gel microspheres with a diameter of about 1 cm, which are the acetone slow-release cores.

[0036] The microbial load shell of this invention is composed of a three-dimensional interconnected macroporous polyurethane foam with a specific pore size (1-4 mm). The pore size can be precisely controlled using processes such as particle leaching to optimize microbial attachment, proliferation, and mass transport. The domesticated AMAO functional bacterial community is immobilized on the pore surface and interior of this polyurethane foam, forming a high-biomass functionalized biofilm layer. The preparation method of this polyurethane shell with a three-dimensional macroporous structure is as follows: S1. Weigh out sodium chloride crystals of a certain particle size (2.5 mm) as a water-soluble pore-forming agent and fill them into a cylindrical mold.

[0037] S2. Mix the polyether-type polyurethane prepolymer with the foaming agent, catalyst, and deionized water in a certain proportion, and quickly pour it into the mold to ensure that the prepolymer is immersed in and surrounds the pore-forming agent particles.

[0038] S3. Cure at 60°C for 2 hours. Immerse the cured polyurethane block in a large amount of deionized water, changing the water every 12 hours until no chloride ions are detected in the water (about 3-5 days) to completely remove sodium chloride crystals by leaching, thereby forming a three-dimensional interconnected macroporous network with a pore size of about 2.5 mm in the polyurethane.

[0039] S4. Cut the obtained porous polyurethane material into the desired shape (such as a cube), leaving a cavity in the center to accommodate the core.

[0040] The prepared wet acetone-releasing core was placed into the central cavity of the prepared polyurethane porous shell. A small amount of polyurethane prepolymer was used as an adhesive for fixation, forming a complete composite microbial carrier. The assembled composite microbial carrier was sterilized, and then immersed in a high-concentration AMAO functional bacterial solution and cultured at 25-30°C with low-speed shaking for 3-7 days. This allowed the bacterial community to adsorb and colonize on the macroporous surface and inside the polyurethane shell, forming a biofilm, thus obtaining the functionalized composite microbial carrier. The AMAO functional bacterial community was obtained by enriching and culturing aquatic sediments with raw water and 10 mg / L acetone for 15 days.

[0041] Please see Figure 2 The figure shows the acetone slow-release curve of the composite microbial carrier in this embodiment during actual remediation. As can be seen from the figure, the slow-release concentration of acetone is between 0.1 mg / L and 5 mg / L, showing a trend of rapid release rate in the early stage and gradual stabilization in the later stage. After 50 days, the acetone concentration can still be maintained at about 0.1 mg / L, ensuring the acetone demand during the implementation process, and has a good slow-release effect.

[0042] Example 2 Please see Figures 3-5 This is a direct ammonia oxidation denitrification device for water remediation, comprising multiple composite microbial carriers as described in Example 1, and a physical structural frame for supporting and fixing the composite microbial carriers; wherein, the physical structural frame may be a bio-rope, a bio-cage, or a floating bio-bed (such as...). Figure 2 , 3 (as shown in Figure 4) or any one of the following: a submerged biogrid.

[0043] In specific implementation, multiple composite microbial carriers from Example 1 are loaded at certain intervals into mesh biocages to form remediation modules. In a landscape water body with an ammonia nitrogen concentration of approximately 8 mg / L, the biocages are submerged to a depth of 0.5 meters at a density of two remediation modules per square meter of water surface. Underwater, acetone-mediated ammonia oxidation functional bacteria are fixed on the three-dimensional interconnected macroporous structure of the microbial load shell. The acetone slow-release core continuously releases low concentrations of acetone, which diffuses to the biofilm area of ​​the microbial load shell to nourish the AMAO bacteria. Ammonia nitrogen in the water diffuses into the microbial load shell, and the AMAO bacteria use the low concentration of acetone diffused from the acetone slow-release core as a circulation mediator to directly oxidize the ammonia nitrogen diffused into the bioload shell into nitrogen gas, thereby achieving in-situ and continuous removal of ammonia nitrogen.

[0044] like Figure 6 As shown in the figure, continuous monitoring shows that after the device was started, the ammonia nitrogen concentration in the water body steadily decreased to below 0.5 mg / L within one month, and remained at around 0.2 mg / L during the subsequent two-month monitoring period, proving that the device has achieved long-term and stable denitrification function.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A composite microbial carrier for direct ammonia oxidation and denitrification in water remediation, characterized in that, Includes an acetone-release core and a bio-load shell; The acetone slow-release core includes a solid adsorbent as the core and a calcium alginate gel layer coated on the core, and acetone is loaded on the solid adsorbent. The slow release of acetone is achieved through the acetone slow-release core. The bioburden shell is made of polyurethane foam with a three-dimensional interconnected macroporous structure, and the acetone-releasing core is encapsulated inside the polyurethane foam. The bioburden shell is used to immobilize acetone-mediated ammonia oxidation functional bacteria, provide a three-dimensional space for microbial attachment, growth and AMAO reaction, and delay the diffusion of acetone to the outside of the bioburden shell.

2. The composite microbial carrier according to claim 1, characterized in that, The acetone loaded on the solid adsorbent exists in the acetone slow-release core in an adsorbed state, forming a first diffusion barrier through the hydrophilic network of the calcium alginate gel layer. The solid adsorbent's retention of acetone provides a secondary slow release.

3. The composite microbial carrier according to claim 2, characterized in that, The solid adsorbent is activated carbon.

4. The composite microbial carrier according to claim 3, characterized in that, The preparation method of the acetone sustained-release core is as follows: S1. Weigh the set amount of pretreated activated carbon powder, immerse it in an acetone aqueous solution with a volume concentration not exceeding 50%, and shake to adsorb until saturation. S2. Filter to obtain wet activated carbon loaded with acetone; S3. Dissolve sodium alginate in deionized water to prepare a 2%~4% (w / v) solution; S4. Mix the wet activated carbon in S2 with the sodium alginate solution prepared in S3 at a mass ratio of 0.5~1:2~3, stir evenly to form a composite slurry; S5. The slurry is dropped dropwise into a 4% (w / v) calcium chloride solution. After the droplets come into contact with the calcium solution, their surfaces quickly cross-link into spheres. S6. After solidification, the product is removed and rinsed with deionized water to obtain wet calcium alginate-activated carbon composite gel microspheres, which are acetone-release cores.

5. The composite microbial carrier according to claim 1, characterized in that, The diameter of the acetone-releasing core is 0.5~2cm; the pore size of the polyurethane foam is 1~4mm.

6. The composite microbial carrier according to claim 5, characterized in that, The three-dimensional interconnected macroporous structure of the bio-load shell is prepared by particle leaching, and the water-soluble porogen used has a particle size of 1~4 mm.

7. The composite microbial carrier according to claim 6, characterized in that, The method for preparing the bio-load shell is as follows: S1. Weigh out sodium chloride crystals of a set particle size as a water-soluble pore-forming agent and fill them into a cylindrical mold. S2. Mix the polyether-type polyurethane prepolymer with the foaming agent, catalyst and deionized water in a certain proportion, and pour it into the mold so that the prepolymer is immersed in and surrounds the pore-forming agent particles. S3. Curing at 60°C, immersing the cured polyurethane block in deionized water, changing the water regularly until no chloride ions are detected in the water, so as to completely remove sodium chloride crystals by leaching, thereby forming a three-dimensional interconnected macroporous network in the polyurethane. S4. Cut the obtained porous polyurethane material into the desired shape, leaving a cavity in the center for inserting the acetone slow-release core.

8. A direct ammonia oxidation denitrification device for water remediation, characterized in that, The invention includes one or more composite microbial carriers as described in any one of claims 1 to 7, and a physical structural framework for supporting and fixing the composite microbial carriers; the physical structural framework is a bio-rope, a bio-cage, a floating bio-bed, or a submerged bio-grid; the three-dimensional interconnected macroporous structure of the bio-load shell is fixed with acetone-mediated ammonia oxidation functional bacteria, which use low-concentration acetone diffused from the acetone slow-release core as a circulation mediator to directly oxidize ammonia nitrogen diffused into the bio-load shell from the water into nitrogen gas.

9. The ammonia direct oxidation denitrification device for water remediation according to claim 8, characterized in that, The composite microbial carriers are spaced apart and mounted on the physical structural framework.

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