A multilayered hybrid nutrient-based extreme denitrification carrier and its preparation and application

Abstract

This invention discloses a multi-layered hybrid nutrient-based extreme nitrogen removal carrier, its preparation, and its application. The multi-layered hybrid nutrient-based extreme nitrogen removal carrier has a core-shell structure, wherein the inorganic core includes autotrophic functional materials and buffer materials, and the multi-layered organic outer shell structure is composited onto the outer layer of the inorganic core through alternating loading of heterotrophic functional materials and structural components, thereby enhancing the controllability of the functional material release process and the carrier's service life. The multi-layered hybrid nutrient-based extreme nitrogen removal carrier is an autotrophic-heterotrophic composite nitrogen removal system, mainly targeting the deep nitrogen removal needs of wastewater treatment plant effluent and surface water with low nitrogen pollution and carbon-nitrogen ratio. It can be used in typical water purification systems represented by biological fluidized beds, biological filters, and constructed wetlands. It does not require the addition of external organic carbon source drugs, and the effluent can meet the Class III water standard of the Surface Water Environmental Quality Standard (GB 3838-2002). It also has the advantages of low cost, simple preparation, wide applicability, and good hydraulic performance.

Description

Technical Field

[0001] This invention relates to the field of deep water treatment technology, and more specifically to a multi-layered hybrid nutrient-based extreme denitrification carrier and its preparation and application. Background Technology

[0002] With increasing attention being paid to the quality of the aquatic ecological environment, higher requirements have been placed on water quality and wastewater treatment plant discharge standards. More and more wastewater treatment plants are adopting the Class A standard requirements of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB 18918-2002), and some are even moving closer to the Class III and IV surface water standards. However, due to the widespread problem of insufficient carbon-to-nitrogen ratios, the removal of total nitrogen from wastewater often fails to meet increasingly stringent discharge standards. Currently, external organic carbon sources (sodium acetate, glacial acetic acid, etc.) are typically added to meet the needs of traditional heterotrophic denitrification processes, which significantly increases operating costs and maintenance complexity. Therefore, autotrophic denitrification processes using inorganic elements such as sulfur, iron, or ferrous iron as electron donors have received increasing attention. A prime example is the development of autotrophic denitrification materials based on materials such as sulfur and reduced iron powder. However, these materials developed solely for autotrophic denitrification processes often suffer from low denitrification efficiency and increased sulfate concentration in the effluent. In addition, existing carriers with carbon source slow-release function often have problems such as uncontrollable carbon source release, which can easily lead to excessive COD in the effluent, and further improvements are needed.

[0003] Therefore, how to provide a stable, slow-release, and highly efficient water denitrification material is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a multi-layered hybrid nutrient-based extreme nitrogen removal carrier, its preparation and application. The multi-layered hybrid nutrient-based extreme nitrogen removal carrier is a sulfur matrix-organic matter composite system. The organic matter not only provides a carbon source for heterotrophic denitrification, but also provides electrons and energy for the denitrification metabolism and growth of iron-autotrophic denitrifying bacteria. The denitrification system configured with this multi-layered hybrid nutrient-based extreme nitrogen removal carrier does not require an external carbon source, and the denitrification efficiency is greatly enhanced compared to the single autotrophic denitrification process. The multi-layered hybrid nutrient-based extreme nitrogen removal carrier is suitable for typical wastewater treatment and water purification systems such as biological fluidized beds, biological filters, and constructed wetlands.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] First, the present invention provides a multi-layered hybrid nutrient-type extreme denitrification carrier, wherein the carrier has a core-shell structure, comprising an inorganic core and an organic shell;

[0007] The inorganic core includes autotrophic functional materials and buffer materials;

[0008] The organic shell comprises alternating layers of heterotrophic functional materials and structural components;

[0009] The mass ratio of the inorganic core, heterotrophic functional material layer, and structural component layer is (6-8):(2-3):(1-3);

[0010] The inorganic core is in contact with the heterotrophic functional material layer.

[0011] Polyhydroxyalkanoates (PHA) can provide a carbon source while guiding the evolution of denitrifying bacteria in the microbial community, thus rapidly enhancing the denitrification performance of the water purification system.

[0012] Preferably, the self-nourishing functional material is sulfur, and the buffering material is one of calcite, aragonite, and dolomite.

[0013] Sulfur participates in the sulfur autotrophic denitrification process as an electron donor, while the buffer material can provide calcium ions to reduce the residual sulfate produced by sulfur autotrophic denitrification in the effluent and adjust the overall density of the carrier.

[0014] Furthermore, the mass ratio of the self-nourishing functional material to the buffer material is (3-7):(1-3).

[0015] Preferably, the heterotrophic functional material is a polyhydroxy fatty acid ester, and the structural component is a mixture of adhesive and foaming agent in a mass ratio of (2-5):1.

[0016] Furthermore, the adhesive is polylactic acid, and the foaming agent is one of sodium α-alkenylsulfonate, azodicarbonamide, and AES synthetic protein.

[0017] This invention also provides a method for preparing the multilayer structured hybrid nutrient-type extreme denitrification carrier described above, comprising the following steps:

[0018] Step 1: Preparation of Inorganic Core

[0019] The self-nourishing functional material and the buffer material are mixed in a certain proportion, then stirred, heated and melted, and then dropped into cold water to cool and granulate to obtain an inorganic core;

[0020] Step 2: Organic shell loading

[0021] The inorganic core obtained in step one is first placed in molten heterotrophic functional material, and after the surface is coated with heterotrophic functional material, it is cooled and shaped. Then it is placed in molten structural component, and after the surface is coated with structural component, it is cooled and shaped. This process is repeated to coat the inorganic core with heterotrophic functional material layer and structural component layer, thus forming a multi-layered structured hybrid nutrient-type extreme denitrification carrier.

[0022] Preferably, in step one, the stirring speed is 200-350 rpm, the stirring time is 300-600 s, and the heating temperature is 170℃-180℃.

[0023] Preferably, in step two, the heterotrophic functional material and structural components are kept in a molten state at a temperature of 130–180°C; cooling and shaping are carried out using cooling water at a temperature of 40–75°C.

[0024] Preferably, the organic shell loading operation is repeated 2 to 5 times in step two.

[0025] Furthermore, the present invention also provides the application of the multilayer structured mixed nutrient type extreme denitrification carrier described in the above scheme and the multilayer structured mixed nutrient type extreme denitrification carrier prepared by the method described in the above scheme, which is applied to water treatment with C / N≤3 and TN≤15mg / L.

[0026] Preferably, the particle size of the inorganic core granulation is determined according to the application scenario of the multi-layer structure mixed nutrient type extreme denitrification carrier. In common application scenarios, the recommended material size is d = 1 to 3 mm in biological fluidized bed systems, d = 2 to 15 mm in biological filter systems, and d = 10 to 50 mm in constructed wetland systems.

[0027] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a multilayer structured hybrid nutrient-type extreme denitrification carrier and its preparation and application, which has the following beneficial effects:

[0028] 1) Traditional biological denitrification processes often require wastewater with a high C / N ratio to ensure the denitrification process is carried out and effective. Therefore, external addition of organic carbon sources such as sodium acetate is often necessary. This invention achieves highly efficient and deep denitrification of low-nitrogen polluted wastewater with a C / N ratio ≤ 3 without the need for external addition of organic carbon sources, mainly relying on a sulfur autotrophic-heterotrophic composite nutrient denitrification process, effectively improving the denitrification efficiency of the water purification system.

[0029] 2) This invention employs a calcium ion buffering strategy to reduce the impact of sulfate byproducts in the autotrophic denitrification process, and simultaneously uses a polylactic acid-PHA alternating multilayer structure to control the slow release rate of autotrophic and heterotrophic functional materials, thereby avoiding excessively high concentrations of sulfate and organic matter in the effluent of the denitrification system, which could cause secondary pollution.

[0030] 3) This invention adopts a multi-layer structure with an outer layer of autotrophic functional material and an inner layer of autotrophic functional material. The outer layer of PHA quickly intervenes in the denitrification process, guides the succession of the denitrification functional bacterial community, and then transforms into an autotrophic-heterotrophic composite nutrient denitrification process, which effectively overcomes the problems of slow start-up and low denitrification load in the autotrophic denitrification process.

[0031] 4) This invention can be widely adapted to typical water purification scenarios represented by biological fluidized beds, biological filters, and constructed wetlands, and has the advantages of low cost, simple preparation, and good hydraulic performance. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the preparation process of a multilayer structured hybrid nutrient-type extreme denitrification carrier according to the present invention;

[0034] Figure 2 This is a schematic diagram illustrating the application of the multilayer structured hybrid nutrient-type extreme denitrification carrier in a biological fluidized bed according to Embodiment 1 of the present invention.

[0035] Figure 3 This is a schematic diagram illustrating the application of the multi-layered mixed nutrient extreme denitrification carrier in a biofilter according to Embodiment 2 of the present invention.

[0036] Figure 4 This is a schematic diagram illustrating the application of the multilayer structured hybrid nutrient-type extreme denitrification carrier in constructed wetlands according to Embodiment 3 of the present invention.

[0037] In the diagram, 1-multi-layered mixed nutrient extreme denitrification carrier, 2-aeration pipe, 3-water inlet, 4-water outlet tank, 5-water outlet, 6-support layer, 7-aquatic plants, 8-coarse sand layer, 9-water distribution pipe, 10-proof layer. Detailed Implementation

[0038] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] As attached Figure 1 The method for preparing the multilayer structured hybrid nutrient-type extreme denitrification carrier includes the following steps:

[0040] Step 1: Preparation of Inorganic Core

[0041] The autotrophic functional material sulfur and the buffer material calcium carbonate mineral are mixed in a mass ratio of (3-7): (1-3), then stirred at 200-350 rpm for 300-600 s, and simultaneously heated to 170-180℃ to melt and then dropped into cold water (40℃) to cool and granulate to obtain an inorganic core.

[0042] Step 2: Organic shell loading

[0043] The inorganic core obtained in step one is first placed in a heterotrophic functional material polyhydroxy fatty acid ester (PHA) kept in a molten state at 130-180℃. After the surface is coated with polyhydroxy fatty acid ester (PHA) and cooled to set, it is then placed in a structural component composed of polylactic acid and foaming agent in a mass ratio of (2-5):1 kept in a molten state at 130-180℃. After the surface is coated with the structural component, it is placed in cooling water (40-75℃). The process is repeated to coat the inorganic core with a heterotrophic functional material layer and a structural component layer, thus forming a multi-layered structured hybrid nutrient-type extreme denitrification carrier.

[0044] The foaming agent is one of sodium α-olefin sulfonate, azodicarbonamide, or AES synthetic protein.

[0045] The multilayered mixed nutrient type extreme denitrification carrier prepared by the above method is prepared and applied as follows:

[0046] Example 1

[0047] The inorganic core component is obtained by mixing the self-nourishing functional material sulfur and the buffering material calcium carbonate mineral aragonite in a mass ratio of 5:2.

[0048] The structural component was obtained by mixing polylactic acid and azodicarbonamide at a mass ratio of 5:1.

[0049] The mass ratio of the inorganic core, autotrophic functional material, and structural components is 6:2:1;

[0050] The heating temperature for the inorganic core melting step is 175℃~180℃, the stirring speed is 300~350rpm, the stirring time is 550~600s, and the particle size is d=1~5mm;

[0051] The organic shell is composited onto the outer layer of the inorganic core by alternating loading of heterotrophic functional materials and structural components. The heterotrophic functional materials and structural components are kept in a molten state at 165-170°C. The alternating loading process involves first dipping the inorganic core into PHA and then placing it in cooling water (40°C) for shaping, and then dipping it into the structural components and placing it in cooling water again for shaping. The above steps are repeated 5 times as needed.

[0052] The prepared multilayered hybrid nutrient-type extreme denitrification carrier was loaded into a biological fluidized bed, as shown in the attached figure. Figure 2As shown, the system adopts an upflow operation and uses a heterotrophic-sulfur autotrophic denitrification process to achieve highly efficient deep treatment of wastewater effluent (TN≤15mg / L, C / N≤3), especially nitrate nitrogen, with the effluent quality reaching the Class III surface water standard (TN≤1.0mg / L; COD≤20mg / L).

[0053] Example 2

[0054] The inorganic core component is obtained by mixing the self-nourishing functional material sulfur and the buffer material calcium carbonate mineral calcite in a mass ratio of 3:1.

[0055] The structural component was obtained by mixing polylactic acid and sodium α-olefin sulfonate in a mass ratio of 5:1.

[0056] The mass ratio of the inorganic core, autotrophic functional material, and structural components is 8:3:3;

[0057] The heating temperature for the inorganic core melting step is 170℃~175℃, the stirring speed is 200~300rpm, the stirring time is 300~400s, and the particle size is d=2~15mm;

[0058] The organic shell is composited onto the outer layer of the inorganic core by alternating loading of heterotrophic functional materials and structural components. The heterotrophic functional materials and structural components are kept in a molten state at 170-180°C. The alternating loading process involves first dipping the inorganic core into PHA and then placing it in cooling water (40°C) for shaping, and then dipping it into the structural components and placing it in cooling water again for shaping. The above steps are repeated 3 times as needed.

[0059] The prepared multi-layered mixed-nutrient extreme denitrification carrier was loaded into a denitrifying biological filter, as shown in the attached figure. Figure 3 As shown, the system adopts an upflow operation and uses a heterotrophic-sulfur autotrophic denitrification process to achieve the ultimate denitrification of nitrate nitrogen in the wastewater treatment plant effluent (TN=8~12mg / L, C / N≤3), and the effluent quality meets the Class III surface water standard (TN≤1.0mg / L; COD≤20mg / L).

[0060] Example 3

[0061] The difference from Example 2 is that the particle size of the inorganic core granulation is d = 10-50 mm, and the prepared multilayer structured mixed nutrient-type extreme denitrification carrier is laid in the constructed wetland, as shown in the attached figure. Figure 4 As shown, the system operates in an upward subsurface flow mode, using a heterotrophic-sulfur autotrophic denitrification process to purify surface water with low nitrogen pollution (TN≤5mg / L) and low carbon-to-nitrogen ratio (C / N≤3) in wetlands. The effluent quality meets the Class III surface water standard (TN≤1.0mg / L; COD≤20mg / L).

[0062] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0063] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a multilayered hybrid nutrient-type extreme denitrification carrier, characterized in that, The carrier has a core-shell structure, comprising an inorganic core and an organic shell; The inorganic core includes autotrophic functional materials and buffer materials; The organic shell comprises alternating layers of heterotrophic functional materials and structural components; The mass ratio of the inorganic core, heterotrophic functional material layer, and structural component layer is (6-8):(2-3):(1-3); The inorganic core is in contact with the heterotrophic functional material layer; The autotrophic functional material is sulfur, and the buffering material is one of calcite, wollastonite, and dolomite; the mass ratio of the autotrophic functional material to the buffering material is (3-7):(1-3); the heterotrophic functional material is polyhydroxy fatty acid ester, and the structural component is a mixture of binder and foaming agent in a mass ratio of (2-5):1; the binder is polylactic acid, and the foaming agent is one of sodium α-olefin sulfonate, azodicarbonamide, and AES synthetic protein; The preparation method includes the following steps: Step 1: Preparation of Inorganic Core The self-nourishing functional material and the buffer material are mixed in a certain proportion, then stirred, heated and melted, and then dropped into cold water to cool and granulate to obtain an inorganic core; Step 2: Organic shell loading The inorganic core obtained in step one is first placed in molten heterotrophic functional material, and after the surface is coated with heterotrophic functional material, it is cooled and shaped. Then it is placed in molten structural component, and after the surface is coated with structural component, it is cooled and shaped. The operation is repeated so that the inorganic core is coated with heterotrophic functional material layer and structural component layer, that is, a multi-layered structured hybrid nutrient type extreme denitrification carrier.

2. The method for preparing a multilayered hybrid nutrient-type extreme denitrification carrier according to claim 1, characterized in that, In step one, the stirring speed is 200-350 rpm, the stirring time is 300-600 s, and the heating temperature is 170℃-180℃.

3. The method for preparing a multilayered hybrid nutrient-type extreme denitrification carrier according to claim 1, characterized in that, In step two, the heterotrophic functional materials and structural components are kept in a molten state at a temperature of 130–180°C; cooling and shaping are done using cooling water at a temperature of 40–75°C.

4. The method for preparing a multilayered hybrid nutrient-type extreme denitrification carrier according to claim 1, characterized in that, In step two, the organic shell loading operation is repeated 2 to 5 times.

5. The application of a multilayered mixed-nutrient extreme denitrification carrier prepared by any one of claims 1-4, characterized in that, It can be applied to water treatment with C / N ≤ 3 and TN ≤ 15 mg / L.

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