Combined modified heavy medium carrier for enhancing anaerobic fermentation and recovery method and application thereof

Abstract

The invention provides a combined modified heavy medium carrier for strengthening anaerobic fermentation and a recovery method and application thereof, the combined modified heavy medium carrier for strengthening anaerobic fermentation comprises a matrix and a plurality of functional layers coating the outer side of the matrix; the base body is a density driving type inorganic dense medium base body, so that the carrier can realize graded sedimentation and recovery in a cyclone separation field based on density difference; the functional layer at least comprises a cationic functional layer and an electron shuttle enhancement layer which are sequentially arranged from inside to outside. The modified dense medium carrier for anaerobic fermentation has a remarkable anaerobic fermentation strengthening effect, and has the characteristics of environment friendliness, economy, easiness in recovery and recyclability.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering technology, specifically relating to a combined modified heavy media carrier for enhanced anaerobic fermentation, its recovery method, and its application. Background Technology

[0002] Current anaerobic fermentation processes face several limiting factors. For example, insufficient effective biomass leads to the easy loss of microorganisms in the effluent, and low hydrolysis rates of substrates such as proteins, lipids, and cellulose severely restrict the anaerobic digestion process. Furthermore, the low efficiency of traditional H2 transfer results in insufficient DIET (Direct Interspecies Electron Transfer), limiting the rate of methane formation. In addition, in the treatment of high-sulfur wastewater, the toxicity of H2S caused by sulfate reduction reactions strongly inhibits the reproduction of methanogens, further affecting the anaerobic fermentation effect. Simultaneously, commonly used carrier materials (such as plastics and porous carbon materials) suffer from numerous drawbacks, including low density, non-recyclability, and difficulty in reusing.

[0003] In currently available technologies, many anaerobic fermentation enhancement carriers rely on materials such as activated carbon, magnetic particles, and iron powder as a matrix for granulation. For example, patent document CN103548094A discloses a composite multilayer carrier material with nanoscale magnetic particles as the matrix. However, although these carrier materials play a role in capture and adsorption, they have failed to effectively solve the problem of anaerobic digestion treatment of enriched organic waste. Furthermore, the application of nanoscale magnetic particles not only complicates the processing and increases production costs, but also requires the design of sophisticated magnetic separation and magnetic recovery processes to ensure the recycling of the carrier, leading to high process costs and poor recovery stability.

[0004] In industrial applications, the shortcomings of these existing technologies limit their effectiveness in treating high-sulfur wastewater and complex wastewater (such as chemical wastewater and leachate from kitchen waste). Therefore, how to provide a composite carrier that can enhance the anaerobic fermentation process, provide comprehensive benefits, and is easy to recycle, has low manufacturing costs, and is suitable for industrial mass production has become a prominent problem that urgently needs to be solved. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a combined modified heavy medium carrier for enhancing anaerobic fermentation and a compatible cyclone recovery method. Through the rational selection of the carrier and the design of its layered structure materials and functions, the high-density characteristics of the heavy medium matrix enable it to effectively adapt to conventional cyclone recovery processes. Simultaneously, the multi-layered coating structure outside the heavy medium matrix efficiently achieves functions such as cation attachment, electron shuttle, and sulfur resistance, effectively enhancing the anaerobic digestion process. Furthermore, the material is designed for easily processed dimensions, eliminating the need for raw materials such as activated carbon, magnetic materials, iron powder, and enzymes, effectively reducing processing difficulty and manufacturing costs.

[0006] To achieve the above-mentioned technical effects, the present invention provides the following solution: Specifically, a first aspect of the present invention provides a combined modified heavy medium carrier for enhancing anaerobic fermentation, comprising a matrix and multiple functional layers covering the outside of the matrix; the matrix is ​​a density-driven inorganic heavy medium matrix, so that the carrier can achieve graded sedimentation and recovery in a swirling separation field based on density difference; the functional layers include at least a cationic functionalized layer and an electron shuttle enhancement layer arranged sequentially from the inside to the outside.

[0007] Optionally, the inorganic matrix is ​​an inorganic particulate material with a density ≥2.8 g / cm³ and a particle size range of 0.1~1.0 mm; the inorganic particulate material is one or more of barite, hematite, corundum, high-density ceramsite, or industrial heavy media powder.

[0008] Optionally, the material of the cationic functionalized layer is one or more of chitosan, chitosan oligosaccharide, cationic polysaccharide, or cationic polymer.

[0009] Optionally, the material of the electron shuttle enhancement layer is one or more of humic acid, fulvic acid, or iron humate.

[0010] Optionally, it also includes a weak iron complex anti-sulfur poisoning layer coated on the outside of the electron shuttle enhancement layer; the weak iron complex anti-sulfur poisoning layer is formed by Fe 3+ It forms a complex with HA on the particle surface.

[0011] A second aspect of the present invention provides a method for recovering the combined modified heavy medium carrier for enhanced anaerobic fermentation, wherein a hydrocyclone is used to recover the heavy medium carrier, and the high density characteristics of the heavy medium are utilized by adjusting the operating parameters of the hydrocyclone to adapt to the heavy medium particles.

[0012] Optionally, the operating parameters include: the inlet velocity of the hydrocyclone is controlled at 2~4 m / s; the underflow diameter is set to 10~18 mm.

[0013] Optionally, a thin anti-wear bushing may be added to the inner wall of the hydrocyclone.

[0014] A third aspect of the present invention provides the application of the combined modified heavy medium carrier for enhancing anaerobic fermentation in biological treatment and anaerobic digestion processes.

[0015] Unlike existing anaerobic reinforcement carriers based on activated carbon, magnetic particles, or iron powder, this invention takes "density-driven recyclability" as its core design constraint. Under the premise of ensuring industrial-scale recycling, it constructs a hierarchical functional synergistic system to achieve a multifunctional integrated carrier structure that enhances microbial attachment, electron transfer, and sulfur toxicity resistance, thus avoiding the problems of magnetic separation dependence and the complexity of nanomaterial processing.

[0016] The beneficial effects of this invention are as follows: (1) Using millimeter-scale high-density inorganic heavy medium particles as the matrix ensures that the raw materials are easy to obtain and process, and are suitable for industrial production. The high density of this matrix enables it to achieve efficient graded sedimentation in a swirling field environment based on density difference. With the parameter adaptation of the hydrocyclone device, it can effectively complete the recovery of heavy medium carriers, avoiding the problems of low efficiency and high cost in the magnetic separation and magnetic recovery process faced by existing magnetic material matrix carriers.

[0017] (2) A cationic functionalized layer and an electron shuttle enhancement layer were sequentially arranged outside the inorganic heavy medium matrix. This design effectively solved the problems of difficult microbial attachment, insufficient effective biomass, and limited DIET process in anaerobic fermentation. To further improve the wastewater treatment effect, a weak iron complex anti-sulfur layer was added outside the electron shuttle enhancement layer, providing a buffer and removal effect against sulfur toxicity in high-sulfur wastewater. Through this reasonable layered design, based on the metabolic mechanism of anaerobic microorganisms, the effect of the anaerobic fermentation process was significantly enhanced.

[0018] Those skilled in the art will understand that the objectives and advantages achievable with the present invention are not limited to those specifically described above, and that the above and other objectives achievable with the present invention will become clearer from the following detailed description. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of this application, but do not constitute a limitation thereof; it should be noted that the drawings themselves are not within the scope of protection of this patent.

[0020] Figure 1 This is a schematic diagram of the combined modified heavy medium carrier particle structure in an embodiment of the present invention; Figure 2 This is a comparison of biogas production before and after the addition of the combined modified heavy medium carrier in an embodiment of the present invention; Figure 3This is a comparison of hydrogen sulfide production before and after the addition of the combined modified heavy medium carrier in this embodiment of the invention; Figure 4 This invention provides a comparison of the impact of the number of cycles on the performance of combined modified heavy media in various embodiments. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention. It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only structures and / or processing steps closely related to the solutions according to the invention are shown in the accompanying drawings, while other details not closely related to the invention are omitted.

[0022] It should be emphasized that the term "comprising / including" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components. Furthermore, the wording related to serial numbers and designations in this disclosure, such as "first," "second," "S1," "S2," and similar expressions, is used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number or necessary order of the indicated technical features, nor does it exclude the presence or addition of one or more other features, elements, steps, or components.

[0023] The following is in conjunction with the appendix Figure 1-4 The embodiments of the present invention will be described in detail and clearly.

[0024] One embodiment of the present invention provides a combined modified heavy medium carrier for enhancing anaerobic fermentation, comprising a matrix and multiple functional layers covering the outside of the matrix; the matrix is ​​a density-driven inorganic heavy medium matrix, so that the carrier can achieve graded sedimentation and recovery in a swirling separation field based on density difference; the functional layers include at least a cationic functionalized layer and an electron shuttle enhancement layer arranged sequentially from the inside to the outside.

[0025] Optionally, the inorganic matrix of the heavy medium is an inorganic particulate material with a density ≥2.8 g / cm³ and a particle size range of 0.1~1.0 mm; the inorganic particulate material is barite (mainly BaSO4), hematite (mainly Fe2O3), corundum (mainly Al2O3), high-density ceramsite, or industrial heavy medium powder. The aforementioned inorganic matrix serves as the core material for calibrating the weight and density of the carrier during the recycling process. Its density setting of ≥2.8 g / cm³ ensures convenient, safe, and effective adaptation to conventional hydrocyclones, aiming to achieve effective recovery of the heavy medium carrier with minimal parameter adjustments. Simultaneously, the matrix material is readily available, its 0.1~1.0 mm size is easily industrially processed, and it does not contain activated carbon, magnetic materials, iron powder, or ferrous mineral particles, eliminating the need to consider the additional costs associated with magnetic material recovery and achieving effective recycling. Preferably, the inorganic matrix does not contain strongly magnetic materials to avoid the process complexity caused by additional magnetic separation steps. In special application scenarios, such as using industrial heavy media powder containing magnetic components, the recycling method can be selected according to the specific system requirements, but this does not affect the core technical concept of the present invention based on density difference separation.

[0026] Optionally, the material of the cationic functionalized layer is one or more of chitosan, chitosan oligosaccharide, cationic polysaccharide, or cationic polymer (such as cationic acrylamide). In this embodiment, the cationic functionalized layer, as the layer closest to the heavy medium substrate, can be uniformly coated on the outside of a substrate with a regular shape (generally spherical, ellipsoidal, or near-spherical) through existing impregnation, curing, and other processes. The materials selected for cationic functionalization mainly rely on properties such as electrostatic adsorption and molecular bridging to directly bind negatively charged microbial cells, rapidly forming granular sludge or biofilm; or they can act as small molecule inducers, stimulating microorganisms to secrete extracellular polymers and regulating quorum sensing to enhance the natural adhesion and synergy between cells, thereby improving the stability and metabolic activity of the aggregates, effectively increasing microbial retention rate, system resistance to disturbance, and methane production efficiency.

[0027] Optionally, the electron shuttle enhancement layer is made of one or more of humic acid (HA), fulvic acid (FA), or iron humate (Fe-HA). These materials, acting as highly efficient electron shuttles, significantly promote direct electron transfer between microorganisms during anaerobic fermentation. The core principle lies in the fact that the redox-active functional groups such as quinone and phenol groups in the molecular structure of these substances can be used by microorganisms as reversible "electron intermediate carriers." This bypasses the slow indirect transfer of hydrogen / formate, allowing symbiotic microbial communities to directly and rapidly exchange electrons, thereby significantly accelerating the decomposition of acetic acid and the generation of methane, improving system stability and gas production efficiency. Optionally, the layer also includes a weak iron-chelated sulfur-resistant layer coating the outside of the electron shuttle enhancement layer; the weak iron-chelated sulfur-resistant layer is formed by Fe... 3+It undergoes a complexation reaction with the carboxyl and phenolic hydroxyl groups in humic acid molecules to form a stable complex structure. This complex structure acts as an immobilized iron source in anaerobic systems, preferentially undergoing precipitation reactions when sulfides diffuse to the carrier surface, thereby achieving in-situ slow-release removal of hydrogen sulfide. Specifically, when treating complex wastewater (such as chemical wastewater with a COD concentration of 10,000~12,000 mg / L), the toxic effects of H2S on the system often need to be considered. Compared to existing treatment methods, Fe... 3+ It complexes with the abundant oxygen-containing functional groups on the surface of HA particles, stably attaching to the surface of microbial aggregates, thus achieving "immobilization" and "slow release" of iron, avoiding the loss of free iron ions or excessively high local concentrations. Furthermore, when dissolved H2S (or HS-) - When it diffuses to the surface of the aggregate, it will react with Fe in the fixed "HA-Fe" complex. 3+ A specific reaction occurs, generating extremely insoluble FeS or Fe2S3 precipitates. This process takes place "at the doorstep" of the methanogenic bacteria community, achieving in-situ and immediate removal of toxic substances. Therefore, the treatment method provided in this embodiment has significant advantages: high iron utilization and minimal loss; simultaneously, it can control the precipitation reaction to occur on the surface of the microorganisms most in need of protection, avoiding the occupation of reactor space by a large amount of non-specific precipitates. HA itself may also act as an electron shuttle, synergistically promoting DIET with iron. DIET is a highly efficient sulfur toxicity control method that integrates slow release, targeting, and multifunctionality. It should also be noted that the iron ions (Fe2S3) in this layer... 3+ It does not exist in particulate form and does not require magnetic powder or ferrous materials as raw materials, which is different from the traditional form of iron ion supply.

[0028] Experimental verification showed that, based on the above matrix and three-layer structure design, the combined modified heavy media carrier of this invention enhanced microbial adhesion by 3-6 times; substrate hydrolysis was improved by 20-40%, specifically manifested in the increase of soluble COD (sCOD), indicating a significant enhancement in the rate at which the substrate was decomposed into soluble organic matter. DIET was significantly enhanced; under the same reaction conditions, compared with the control group without the loading medium, methane yield increased by 25%-60%; H2S generation decreased by 40%-70%; and the combined modified heavy media carrier maintained 80-90% of its activity after being recycled at least 10 times.

[0029] Furthermore, when the second layer uses iron humate (Fe-HA), its main function is to enhance electron transfer and promote methane production during anaerobic fermentation. The Fe-HA in the third layer specifically addresses sulfur toxicity by stabilizing the release of iron ions through a complexation reaction with humic acid, forming a slow-release sulfur buffer system. This effectively mitigates the toxic effects of H2S (hydrogen sulfide) in the wastewater and protects the activity of the anaerobic microbial community. Therefore, in this specific context, although both the second and third layers use Fe-HA, their functions and mechanisms of action differ significantly, ensuring a synergistic effect between the two.

[0030] The second aspect of the present invention provides a method for recovering a combined modified heavy medium carrier for enhanced anaerobic fermentation. The method uses a hydrocyclone to recover the heavy medium carrier and utilizes the high density characteristics of the heavy medium by adjusting the operating parameters of the hydrocyclone to suit the heavy medium particles.

[0031] Optionally, the operating parameters include: controlling the inlet flow velocity of the hydrocyclone at 2~4 m / s; and setting the underflow diameter to 10~18 mm. In this embodiment, only a conventional commercial hydrocyclone is considered. For example, in this embodiment, a hydrocyclone model of huayan-xlq002 is selected, with a feed pressure of approximately 0.3~1.5 bar, an underflow diameter of 10~18 mm, and an overflow diameter of 30~40 mm. By adjusting the parameters of this hydrocyclone, effective recovery of heavy media carriers can be achieved. Utilizing the high density characteristics of heavy media, a recovery rate as high as 90~99% can be obtained, and the solid mass fraction of the treated underflow is 70~90%.

[0032] Optionally, a thin anti-wear bushing can be added to the inner wall of the hydrocyclone.

[0033] The third aspect of this invention provides an application of a combined modified heavy medium carrier for enhancing anaerobic fermentation in biological treatment and anaerobic digestion processes.

[0034] The following is combined Figure 1-4 The present invention will be further described in detail through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0035] Example 1: Hematite + cationic polysaccharide + HA modified carrier Hematite (Fe2O3, particle size 0.3–0.6 mm) was used as the carrier matrix, and its surface was functionalized with cationic polysaccharides (such as cationic polyacrylamide, concentration 0.5–1.0 wt%) to enhance microbial adhesion. Then, humic acid (HA, concentration 0.5–1.0 g / g carrier) was coated on the carrier surface to enhance electron transfer and promote the acetic acid pathway.

[0036] Reactor parameters: Temperature: 35℃, pH: 7.2.

[0037] Results: When treating high COD wastewater (initial COD concentration of 8000~10,000 mg / L), methane yield was increased by 40% and substrate hydrolysis rate was increased by 30%.

[0038] Example 2: Corundum + Chitosan Oligosaccharide + Fe-HA Modified Carrier Corundum (Al₂O₃, particle size 0.4–0.8 mm) was used as the matrix material, and the surface was impregnated with chitosan oligosaccharide (concentration 1.5–2.0 wt%) to enhance its cationic adsorption capacity and microbial adhesion. Next, a Fe-HA layer (Fe-HA concentration 0.2–0.5 g / g carrier) was applied to enhance electron transfer, thereby accelerating the acetic acid pathway.

[0039] Reactor parameters: Temperature: 30℃, pH: 6.8.

[0040] Results: When treating wastewater containing a large amount of cellulose (such as leachate from kitchen waste with a COD concentration of 6,000~8,000 mg / L), the methane yield increased by 50%, the substrate hydrolysis rate increased by 35%, and the degradation rate of organic matter reached 60%.

[0041] Example 3: Ceramsite + Chitosan + FA-modified carrier Ceramsite (particle size 0.6–1.2 mm) was used as the matrix material, and the surface was impregnated with chitosan (concentration 1.0–1.5 wt%) to enhance microbial adhesion. Next, fulvic acid (FA, concentration 0.3–0.5 g / g carrier) was applied to promote electron transfer.

[0042] Reactor parameters: Temperature: 30℃, pH: 7.0.

[0043] Results: When treating low-sulfur wastewater (such as municipal sewage with COD concentration of 3,000–5,000 mg / L), methane yield was increased by 25% and substrate hydrolysis rate was increased by 20%.

[0044] Example 4: Three-layer coated heavy medium mixing system like Figure 1 As shown, a composite modified carrier with a particle size of 0.3–1.0 mm was prepared by mixing barite, hematite, and high-density ceramsite in a 1:1:1 mass ratio. The first layer used a cationic polymer (0.5 wt%), the second layer used a combination of HA (0.5 g / g carrier) and FA (0.3 g / g carrier), and the third layer used an iron complex (Fe-HA, 0.2 g / g carrier) to reduce sulfur toxicity.

[0045] Reactor parameters: Temperature: 40℃, pH: 7.5.

[0046] Results: When treating complex wastewater (such as chemical wastewater with COD concentration of 10,000~12,000 mg / L), the system increased methane yield by 55%, substrate hydrolysis rate by 40%, and effectively reduced the toxic effects of H2S on the system. Figure 2 This example shows a comparison of biogas production before and after the addition of the modified heavy medium carrier, demonstrating the effect of this system on increasing biogas production.

[0047] In other embodiments, the mass ratio of the three heavy media materials can be (1~3):(1~3):(1~3), preferably 1:1:1 as in this embodiment.

[0048] Example 5: Anaerobic fermentation of high-sulfur wastewater The heavy media carrier system described in Example 4 was applied to the anaerobic treatment of high-sulfur wastewater. By adding a third weak iron complex anti-sulfur layer (Fe-HA), the generation of H2S can be effectively reduced, thereby avoiding toxicity to methanogens and ensuring stable system operation.

[0049] Reactor parameters: Temperature: 35℃, pH: 6.8.

[0050] Results: When treating high-sulfur wastewater (such as petrochemical wastewater with COD concentration of 6,000~8,000 mg / L and sulfur content of 2~3 g / L), the H2S reduction rate reached 60% and the methane yield increased by 45%.

[0051] Figure 3 The comparison of hydrogen sulfide (H2S) production before and after the addition of the modified heavy medium carrier in this embodiment is shown, demonstrating the effect of the heavy medium carrier system in reducing hydrogen sulfide production.

[0052] Example 6: Hydrocyclone Parameter Adaptation and Recovery By taking advantage of the high density characteristics of the heavy medium carrier in Example 4, the operating parameters of the hydrocyclone (such as an inlet velocity of 2.5~3.5 m / s and an underflow diameter of 14 mm) can be slightly adjusted to enable the efficient recovery of these high-density particles.

[0053] Reactor parameters: hydrocyclone operating velocity: 3.0 m / s, underflow diameter: 14 mm. Results: The recovery rate was 90%, and the underflow solids mass fraction was 80%, which effectively separated and recovered heavy media particles.

[0054] Figure 4The effect of the number of recycling cycles on the performance of the modified heavy media carrier in this embodiment is shown, demonstrating that the carrier material can maintain good performance even after multiple recycling cycles.

[0055] Example 7: Enhanced Anaerobic Fermentation of Kitchen Waste This embodiment utilizes a modified heavy media carrier to enhance the anaerobic fermentation process of food waste. By adding an appropriate amount of modified carrier to the food waste, after a period of anaerobic fermentation, the substrate hydrolysis rate is significantly increased by 20% to 40%, and the methane yield is increased by 25% to 60%.

[0056] Reactor parameters: Temperature: 35℃, pH: 7.2.

[0057] Results: When treating food waste (COD concentration of 6,000–8,000 mg / L), the substrate hydrolysis rate was increased by 35% and the methane yield was increased by 50%.

[0058] Therefore, this invention, starting from fully meeting the needs of enhanced anaerobic fermentation, is based on an in-depth analysis of the reaction mechanism, rationally selecting high-density inorganic heavy media materials as the matrix material, and simplifying the recycling process while ensuring reasonable processing difficulty. Considering the difficulties in microbial attachment, low reaction rates, and the easy generation of sulfur toxicity during anaerobic fermentation, a 2-3 layer coating structure was designed to specifically enhance microbial attachment, improve electron transfer efficiency, and alleviate sulfur toxicity. The resulting combined modified heavy media carrier exhibits a significant anaerobic fermentation enhancement effect and possesses the advantages of being economical, easy to process, and recyclable. By combining it with a suitable cyclone recovery method, the carrier can be efficiently recovered and recycled. This invention breaks through the bottlenecks of existing technologies, optimizes the comprehensive performance and industrial operability of the carrier material, and has high theoretical significance and broad engineering application value.

[0059] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A combined modified heavy media carrier for enhancing anaerobic fermentation, comprising a matrix and multiple functional layers coating the outside of the matrix, characterized in that: The matrix is ​​a density-driven inorganic heavy medium matrix, so that the carrier can achieve graded sedimentation and recovery in a swirling separation field based on density difference; The functional layer includes at least a cationic functionalized layer and an electron shuttle enhancement layer arranged sequentially from the inside out.

2. The combined modified heavy medium carrier for anaerobic fermentation according to claim 1, characterized in that: The inorganic matrix is ​​an inorganic particulate material with a density ≥2.8 g / cm³ and a particle size range of 0.1~1.0 mm; The inorganic particulate material is one or more of barite, hematite, corundum, high-density ceramsite, or industrial heavy media powder.

3. The combined modified heavy medium carrier for anaerobic fermentation according to claim 2, characterized in that: The material of the cationic functionalized layer is one or more of chitosan, chitosan oligosaccharide, cationic polysaccharide or cationic polymer.

4. The combined modified heavy medium carrier for anaerobic fermentation according to claim 2, characterized in that: The electron shuttle enhancement layer is made of one or more of humic acid, fulvic acid, or iron humate.

5. The combined modified heavy medium carrier for anaerobic fermentation according to claim 2, characterized in that: It also includes a weak iron complex anti-sulfur layer covering the outside of the electron shuttle enhancement layer; The weak iron complex anti-sulfur layer is obtained through Fe 3+ It forms a complex with HA on the particle surface.

6. A method for recovering the combined modified heavy medium carrier for enhanced anaerobic fermentation as described in any one of claims 1-5, characterized in that: Hydrocyclones are used to recover heavy media carriers. The high density of heavy media is utilized, and the operating parameters of the hydrocyclones are adjusted to suit the heavy media particles.

7. The recycling method according to claim 6, characterized in that, The operating parameters include: The inlet velocity of the hydrocyclone is controlled at 2~4 m / s; the underflow diameter is set to 10~18 mm.

8. The recycling method according to claim 7, characterized in that: A thin anti-wear bushing is added to the inner wall of the hydrocyclone.

9. The application of the combined modified heavy medium carrier for enhancing anaerobic fermentation as described in any one of claims 1-5 in biological treatment and anaerobic digestion processes.

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