A biological carrier, a preparation method and application thereof

Abstract

The present application relates to the technical field of anaerobic digestion treatment of wastewater, and particularly relates to a biological carrier, a preparation method and application thereof.The biological carrier comprises: a polyethylene biological carrier; a polyurethane adhesive layer compounded on the surface of the polyethylene biological carrier; and a conductive material functional layer compounded on the surface of the polyurethane adhesive layer.The biological carrier provided by the present application uses castor oil-based adhesive in the preparation process, and has high adhesion; after the conductive material is adhered and solidified, the combination is firm and not easy to fall off.Moreover, castor oil as a bio-based polyol has less toxic effect on microorganisms, and is more conducive to the attachment and growth of microorganisms.Meanwhile, the conductive material is only attached to the surface, thereby reducing the amount of material used, saving the operation and dosing cost, being economic and friendly, and being conducive to the attachment of organisms and the occurrence of the DIET process.The biological carrier provided by the present application can be applied to anaerobic digestion treatment of wastewater, and finally a better COD removal rate and methanogenic capacity can be obtained.

Description

Technical Field

[0001] This invention relates to the field of anaerobic digestion treatment technology for wastewater, and particularly to a biological carrier, its preparation method, and its application. Background Technology

[0002] Anaerobic digestion has become a widely used water treatment technology due to its significant advantages in the treatment of high-concentration organic wastewater and solid waste. It has the ability to efficiently utilize substrate resources and recover energy (H2, CH4), while also having the advantages of low sludge production and low energy consumption.

[0003] Anaerobic digestion comprises four main stages: hydrolysis, acidification, hydrogen and acetic acid production, and methanogenesis. This process involves a rich diversity of microorganisms and complex interactions among them. Among these, methanogenic archaea are the most sensitive to environmental changes, making the balance of symbiotic metabolism between acidogenic bacteria and methanogenic archaea directly crucial to the stability of the digestion process. Traditional symbiotic metabolism is an interspecies hydrogen transfer (IHT) process using small-molecule H2 as the electron carrier. However, excessively high H2 partial pressure leads to unfavorable thermodynamics and significant mass transfer resistance. Adding conductive materials can establish a faster direct interspecies electron transfer (DIET) pathway for symbiotic metabolism, maintaining the stability of anaerobic digestion and improving digestion performance. Therefore, to further prevent the loss of conductive materials during reactor operation and reduce addition costs, while providing more contact and attachment sites for functional microorganisms, researchers have recently explored methods such as adhesive bonding and extrusion blending to achieve the bonding of functional materials with carriers—that is, the conductive modification of the carrier.

[0004] Regarding adhesive bonding methods for modifying carrier functions, most inventions focus on first uniformly mixing functional materials with an adhesive solution to obtain a functional coating, and then applying the functional coating to the carrier for curing to obtain a conductive carrier. For example, patent CN202110441809.8 describes a biofilm composite carrier obtained by mixing a zeolite-tourmaline mixture with a water-based polyurethane adhesive and then applying it to a polyurethane sponge skeleton, achieving improved autotrophic denitrification capacity under low temperature and low ammonia nitrogen conditions. Another example is patent CN200510062392.5, which describes a conductive coating obtained by mixing carbon-based conductive materials, dispersants (i.e., stabilizers) with polyurethane coatings or polyacrylate coatings and then applying it to the anode and cathode of an electrolytic cell, achieving improvements in antibiotic wastewater treatment and denitrification processes. However, this adhesive bonding method still has certain problems: 1) In this method, a large portion of the conductive material is bonded internally and not exposed on the surface to function, resulting in increased application costs; 2) Water-based polyurethane adhesives have high hydrophilicity, which may lead to material detachment during long-term operation. Regarding extrusion methods for modifying carrier functionality, patent CN201910521430.0 describes mixing polyethylene, graphite, and other powdered raw materials and then preparing an electron-medium type biological carrier through a granulator and a single-screw extruder to improve anaerobic digestion performance. However, this method of carrier modification is relatively complex and involves high energy input costs. Furthermore, the COD removal rate and methanogenic capacity of existing technologies need further improvement. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a biological carrier, its preparation method and application. The biological carrier provided by the present invention can be applied to the anaerobic digestion treatment of wastewater, and can ultimately obtain better COD removal rate and methanogenic capacity.

[0006] The biological carrier provided by this invention has the advantages of stable operation, cost-effectiveness, and more efficient electron transfer process. The stable operation is reflected in the fact that the conductive material is not easy to fall off during long-term operation. The cost-effectiveness is reflected in the low demand for conductive material and the high exposure of conductive material on the carrier surface. The more efficient electron transfer process is reflected in the mixing of iron-based and carbon-based conductive materials, which makes up for the limited DIET enhancement when each is added alone.

[0007] This invention provides a biological carrier, comprising:

[0008] Polyethylene biological carrier;

[0009] A polyurethane adhesive layer laminated onto the surface of the polyethylene biocarrier;

[0010] A conductive material functional layer is laminated onto the surface of a polyurethane adhesive layer.

[0011] Preferably, the polyethylene biological carrier includes K1 type suspended carrier packing, K2 type suspended carrier packing or K3 type suspended carrier packing.

[0012] Preferably, the polyurethane adhesive layer is prepared from raw materials including component a and component b;

[0013] Component a includes castor oil;

[0014] Component b includes at least one of polymeric MDI, TDI, MDI, HDI, IPDI, and PAPI;

[0015] The volume ratio of component a to component b is 3.5 to 5.5:1.

[0016] Preferably, the thickness of the polyurethane adhesive layer is 0.04 to 0.3 mm.

[0017] Preferably, the conductive material of the conductive material functional layer includes at least one of carbon-based conductive materials and iron-based conductive materials;

[0018] The carbon-based conductive material includes at least one of biochar, activated carbon, conductive graphite, graphene, carbon nanotubes, carbon cloth, carbon fiber, and carbon black.

[0019] The iron-based conductive material includes at least one of zero-valent iron, iron(II,III) oxide, and iron(III) oxide.

[0020] Preferably, the conductive material is biochar; or the conductive material is conductive graphite; or the conductive material is iron(III) oxide; or the conductive material is obtained by mixing biochar and iron(III) oxide, wherein the mass ratio of biochar to iron(III) oxide is 0.7–1.3:1–1.5; or the conductive material is obtained by mixing conductive graphite and iron(III) oxide, wherein the mass ratio of conductive graphite to iron(III) oxide is 0.5–1.2:0.8–1.3.

[0021] Preferably, the thickness of the conductive material functional layer is 0.01 to 0.3 mm.

[0022] Preferably, the mass ratio of the polyethylene biocarrier, the polyurethane adhesive layer, and the conductive material functional layer is 3-3.5:1-2.5:0.5-3.

[0023] This invention also provides a method for preparing the biological carrier described above, comprising the following steps:

[0024] A) Place the polyethylene biocarrier in a polyurethane adhesive, stir and mix well, and then remove it to obtain an adhesive carrier substrate.

[0025] B) The viscous carrier substrate is placed in a conductive material solid powder, stirred and mixed evenly, and then dried and cured to obtain a biological carrier.

[0026] The present invention also provides an application of the biological carrier described above or the biological carrier prepared by the method described above in the field of anaerobic digestion treatment of wastewater.

[0027] This invention provides a biological carrier, comprising: a polyethylene biological carrier; a polyurethane adhesive layer laminated on the surface of the polyethylene biological carrier; and a conductive material functional layer laminated on the surface of the polyurethane adhesive layer. The functional biological carrier for surface conductive modification used to enhance anaerobic digestion provided by this invention utilizes a castor oil-based adhesive during preparation, which exhibits high adhesion. Once the conductive material is bonded and cured, it is firmly attached and not easily detached. Furthermore, castor oil, as a bio-based polyol, has less toxicity to microorganisms, thus promoting microbial attachment and growth. Simultaneously, the conductive material adheres only to the surface, reducing material usage and saving operating costs, making it economical and beneficial for bioattachment and the DIET process. The biological carrier provided by this invention can be applied to anaerobic wastewater digestion treatment, ultimately achieving superior COD removal rates and methanogenic capacity. Attached Figure Description

[0028] Figure 1 A schematic diagram of the structure of a biological carrier provided in one embodiment of the present invention;

[0029] Figure 2 A physical image of a biological carrier provided for one embodiment of the present invention. Detailed Implementation

[0030] 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.

[0031] This invention provides a biological carrier, comprising:

[0032] Polyethylene biological carrier;

[0033] A polyurethane adhesive layer laminated onto the surface of the polyethylene biocarrier;

[0034] A conductive material functional layer is laminated onto the surface of a polyurethane adhesive layer.

[0035] Figure 1This is a schematic diagram of the structure of a biological carrier provided in an embodiment of the present invention; wherein, 1 is a polyethylene biological carrier, 2 is a polyurethane adhesive layer, and 3 is a conductive material functional layer.

[0036] Figure 2 A physical image of a biological carrier provided for one embodiment of the present invention.

[0037] In some embodiments of the present invention, the polyethylene biocarrier includes K1-type suspended carrier packing, K2-type suspended carrier packing, or K3-type suspended carrier packing. The present invention does not impose any special restrictions on the source or type of the K1-type, K2-type, and K3-type suspended carrier packing, which can be commercially available. The thickness of the polyethylene biocarrier substrate is 0.4–0.8 mm; for example, 0.4 mm.

[0038] In some embodiments of the present invention, the polyurethane adhesive layer is prepared from raw materials including component a and component b;

[0039] Component a includes castor oil;

[0040] Component b includes at least one of polymeric MDI, TDI, MDI, HDI, IPDI, and PAPI;

[0041] The volume ratio of component a to component b is 3.5 to 5.5:1, preferably 4:1.

[0042] In some embodiments of the present invention, the thickness of the polyurethane adhesive layer is 0.04 to 0.3 mm, for example, 0.2 mm.

[0043] In some embodiments of the present invention, the conductive material of the conductive material functional layer includes at least one of carbon-based conductive materials and iron-based conductive materials. The carbon-based conductive material includes at least one of biochar, activated carbon, conductive graphite, graphene, carbon nanotubes, carbon cloth, carbon fiber, and carbon black, preferably biochar or conductive graphite. The iron-based conductive material includes at least one of zero-valent iron, magnetite (Fe3O4), and ferric oxide (Fe2O4), preferably magnetite (Fe3O4).

[0044] In some embodiments of the present invention, the conductive material of the conductive material functional layer is preferably composed of the following five components: 1) the conductive material is biochar; 2) the conductive material is conductive graphite; 3) the conductive material is iron(III) oxide; 4) the conductive material is obtained by mixing biochar and iron(III) oxide; 5) the conductive material is obtained by mixing conductive graphite and iron(III) oxide.

[0045] In some embodiments of the present invention, the method for preparing the biochar includes the following steps:

[0046] a1) The sawdust was pretreated by soaking in an acidic solution, then washed and dried to obtain pretreated sawdust;

[0047] a2) Pyrolysis is carried out under oxygen-free conditions;

[0048] a3) After grinding and sieving, biochar is obtained.

[0049] In step a1):

[0050] In some embodiments of the present invention, the acidic solution is a 5wt% to 20wt% hydrochloric acid solution, preferably a 15wt% hydrochloric acid solution.

[0051] In some embodiments of the present invention, the soaking time is 0.5 to 3 hours, preferably 1.5 hours.

[0052] In some embodiments of the present invention, the cleaning process includes rinsing with deionized water until the pH value of the cleaning solution after cleaning is close to neutral, for example, a pH value of 6.5 to 7.5, preferably 7.0.

[0053] In some embodiments of the present invention, the drying process is completed in an oven; the drying temperature is 35-60°C, preferably 60°C.

[0054] In step a2):

[0055] In some embodiments of the present invention, the condition of isolating oxygen is achieved by introducing high-purity nitrogen gas before pyrolysis heating; the time for introducing nitrogen gas before pyrolysis heating is 20 to 60 minutes, preferably 30 minutes; the nitrogen gas flow rate is 60 to 200 sccm, preferably 80 sccm; and the purity of the high-purity nitrogen gas is 99.99%.

[0056] In some embodiments of the present invention, the pyrolysis process is completed in a tube furnace; the pyrolysis temperature is 200-600°C, preferably 600°C; the pyrolysis time is 2-3 hours, preferably 3 hours; and the heating rate to the pyrolysis temperature is 5°C / min.

[0057] In some embodiments of the present invention, the process after pyrolysis further includes cooling.

[0058] In step a3):

[0059] In some embodiments of the invention, the grinding process is performed in a mortar.

[0060] In some embodiments of the present invention, the sieve used for sieving is 100 to 500 mesh, preferably 200 mesh.

[0061] In some embodiments of the present invention, the conductive material is obtained by mixing biochar and iron oxide, specifically by mixing biochar and iron oxide and then ball milling; the conductive material is obtained by mixing conductive graphite and iron oxide, specifically by mixing conductive graphite and iron oxide and then ball milling.

[0062] The mass ratio of biochar to iron oxide is 0.7–1.3:1–1.5, preferably 1:1;

[0063] The mass ratio of conductive graphite to iron oxide is 0.5–1.2:0.8–1.3, preferably 1:1;

[0064] The ball milling process was carried out under an N2 gas atmosphere; the ball milling conditions were: 300 rpm for 2 minutes, followed by a 20-minute pause, and repeated 5 times.

[0065] In some embodiments of the present invention, the thickness of the conductive material functional layer is 0.01 to 0.3 mm, for example, 0.3 mm.

[0066] In some embodiments of the present invention, the mass ratio of the polyethylene biocarrier, the polyurethane adhesive layer and the conductive material functional layer is 3-3.5:1-2.5:0.5-3, preferably 3:1:1.2-2.

[0067] This invention also provides a method for preparing the biological carrier described above, comprising the following steps:

[0068] A) Place the polyethylene biocarrier in a polyurethane adhesive, stir and mix well, and then remove it to obtain an adhesive carrier substrate.

[0069] B) The viscous carrier substrate is placed in a conductive material solid powder, stirred and mixed evenly, and then dried and cured to obtain a biological carrier.

[0070] In step A):

[0071] In some embodiments of the present invention, the polyurethane adhesive is obtained by mixing component a and component b. The mixing is performed by stirring.

[0072] In some embodiments of the present invention, the mass ratio of the polyethylene biocarrier to the polyurethane adhesive is 3-3.5:1-2.5, preferably 3:1.

[0073] In step B):

[0074] In some embodiments of the present invention, the drying temperature is 35-60°C, preferably 60°C; and the drying time is 12-24 hours, preferably 12 hours.

[0075] In some embodiments of the present invention, after drying and curing, the method further includes:

[0076] The substrate is ultrasonically cleaned 2-3 times with deionized water to remove any conductive material solid powder that has not adhered to the adhesive carrier substrate. After cleaning, it needs to be dried and cured to obtain the biological carrier. The re-drying temperature is 35-60℃, preferably 60℃; the re-drying time is 12-24 hours, preferably 12 hours.

[0077] This invention also provides an application of the biological carrier described above or the biological carrier prepared by the method described above in the field of anaerobic wastewater digestion treatment. Specifically, it provides an application of the biological carrier described above or the biological carrier prepared by the method described above as a suspended packing material in anaerobic wastewater digestion treatment. In anaerobic wastewater digestion treatment, the biological carrier can serve as a suspended packing material, providing a habitat for microorganisms to attach, grow, and perform certain functions.

[0078] Beneficial effects:

[0079] (1) The functional biological carrier for surface conductive modification for enhancing anaerobic digestion provided by the present invention uses castor oil-based adhesive in the preparation process. The adhesive has high adhesion. Once the conductive material is bonded and cured, it is firmly bonded and not easy to fall off. The operating cycle can be as long as 40 to 60 days.

[0080] (2) The functional biological carrier for surface conductive modification for enhancing anaerobic digestion provided by the present invention preferably uses castor oil-based polyurethane adhesive as the adhesive used in the preparation process. Castor oil, as a bio-based polyol, has less toxicity to microorganisms and is more conducive to the attachment and growth of microorganisms.

[0081] (3) The functional biological carrier with surface conductive modification for enhancing anaerobic digestion provided by the present invention has conductive material attached only to the surface, which reduces the amount of material used and saves operating costs, making it economical and friendly. At the same time, compared with the existing carrier modification method of coating after mixing conductive material with adhesive, it increases the surface exposure of conductive material, which is more conducive to biological attachment and the occurrence of DIET process.

[0082] (4) The functional biological carrier with surface conductive modification for enhancing anaerobic digestion provided by the present invention uses conductive materials that are not limited to single carbon-based or iron-based materials, and can further improve the electron transfer capability at all scales (i.e., electron transfer over short and long distances).

[0083] (5) The functional biological carrier provided by the present invention enhances the interspecies electron transfer of microorganisms while providing microbial attachment, thereby improving the efficiency of anaerobic digestion and the ability to produce methanogens.

[0084] The present invention does not impose any special restrictions on the source of the raw materials used above, and they can be commercially available.

[0085] To further illustrate the present invention, the following detailed description of a biological carrier, its preparation method and application provided by the present invention is provided in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0086] Example 1

[0087] Preparation of polyurethane adhesives :

[0088] Castor oil and polymeric MDI were mixed evenly at a volume ratio of 4:1 to obtain a polyurethane adhesive.

[0089] Preparation of conductive biochar :

[0090] 1) The sawdust was pretreated by soaking it in a 15wt% hydrochloric acid solution for 1.5 hours, then washed with deionized water until the pH of the washing solution was 7.0, and dried in an oven at 60℃ to obtain pretreated sawdust.

[0091] 2) The pretreated wood chips were placed in an alumina ceramic boat and placed in a tube furnace. High-purity nitrogen (99.99% purity) was first introduced at a flow rate of 80 sccm for 30 min to isolate oxygen. Then the temperature was increased to 600℃ at a heating rate of 5℃ / min and pyrolyzed for 3 h. After cooling, the raw material of biochar was obtained.

[0092] 3) The biochar raw material is ground in a mortar and then passed through a 200-mesh sieve to obtain biochar.

[0093] Preparation of biological carriers :

[0094] 1) Place the polyethylene biological carrier (K1 type suspended carrier filler) in the polyurethane adhesive, stir and mix well, and then take it out to obtain a viscous carrier substrate;

[0095] The mass ratio of the polyethylene biocarrier to the polyurethane adhesive is 3:1;

[0096] 2) Place the adhesive carrier substrate in the biochar, stir and mix evenly, dry and cure at 60°C for 12 hours, then ultrasonically clean with deionized water twice to remove biochar that is not adhered to the adhesive carrier substrate, and dry and cure at 60°C for 12 hours to obtain the biological carrier.

[0097] The biological carrier includes :

[0098] Polyethylene biological carrier (K1 type suspended carrier filler), with a thickness of 0.4 mm;

[0099] The polyurethane adhesive layer laminated onto the surface of the polyethylene biocarrier has a thickness of 0.2 mm.

[0100] A conductive material functional layer (conductive material is biochar) is laminated on the surface of the polyurethane adhesive layer, with a thickness of 0.3 mm.

[0101] The biological carrier was added to the anaerobic digestion moving bed biofilm reactor, with the added biological carrier accounting for 20% of the reactor's working volume. The COD concentration of the reactor influent was 1800 mg / L (including 288.46 mg / L of ethanol, 769.24 mg / L of anhydrous sodium acetate, and 512.82 mg / L of sodium propionate, i.e., ethanol COD equivalent: anhydrous sodium acetate COD equivalent: sodium propionate COD equivalent = 1:1:1). The hydraulic retention time of the reactor was 24 h. The COD removal rate of the anaerobic digestion moving bed biofilm reactor was measured, and the methanogenesis performance was monitored. The results are shown in Table 1.

[0102] Example 2

[0103] The conductive material in Example 1 was changed to conductive graphite, and the remaining steps were carried out in accordance with Example 1 to obtain a biological carrier.

[0104] Following the test method of Example 1, the COD removal rate of the anaerobic digestion moving bed biofilm reactor was determined and the methanogenic performance was monitored. The results are shown in Table 1.

[0105] Example 3

[0106] The conductive material in Example 1 was changed to iron(III) oxide, and the remaining steps were carried out in accordance with Example 1 to obtain the biological carrier.

[0107] Following the test method of Example 1, the COD removal rate of the anaerobic digestion moving bed biofilm reactor was determined and the methanogenic performance was monitored. The results are shown in Table 1.

[0108] Example 4

[0109] The conductive material in Example 1 was changed to a conductive material composed of a mixture of biochar and iron oxide (the total mass of the conductive material was the same). The conductive material composed of the mixture of biochar and iron oxide was prepared according to the following steps:

[0110] The biochar and iron oxide were mixed evenly by ball milling in an N2 atmosphere at a mass ratio of 1:1. The ball milling conditions were: 300 rpm for 2 min, followed by a 20 min pause, and repeated 5 times.

[0111] The remaining steps were performed in accordance with Example 1 to obtain the biological vector.

[0112] Following the test method of Example 1, the COD removal rate of the anaerobic digestion moving bed biofilm reactor was determined and the methanogenic performance was monitored. The results are shown in Table 1.

[0113] Example 5

[0114] The conductive material in Example 1 was changed to a conductive material composed of a mixture of conductive graphite and iron oxide (the total mass of the conductive material is the same). The conductive material composed of the mixture of conductive graphite and iron oxide was prepared according to the following steps:

[0115] The conductive graphite and iron oxide are mixed evenly by ball milling in an N2 atmosphere at a mass ratio of 1:1. The ball milling conditions are: ball milling at 300 rpm for 2 minutes, followed by a 20-minute pause, and repeated 5 times.

[0116] The remaining steps were performed in accordance with Example 1 to obtain the biological vector.

[0117] Following the test method of Example 1, the COD removal rate of the anaerobic digestion moving bed biofilm reactor was determined and the methanogenic performance was monitored. The results are shown in Table 1.

[0118] Example 6

[0119] The COD concentration of the reactor influent in Example 1 was changed to 3600 mg / L (including 576.92 mg / L of ethanol, 1538.48 mg / L of anhydrous sodium acetate, and 1025.64 mg / L of sodium propionate, i.e., ethanol COD equivalent: anhydrous sodium acetate COD equivalent: sodium propionate COD equivalent = 1:1:1), and the hydraulic retention time of the reactor was 24 h. The COD removal rate of the anaerobic digestion moving bed biofilm reactor was measured and the methanogenic performance was monitored. The results are shown in Table 1.

[0120] Example 7

[0121] The COD concentration of the reactor influent in Example 2 was changed to 3600 mg / L (including 576.92 mg / L of ethanol, 1538.48 mg / L of anhydrous sodium acetate, and 1025.64 mg / L of sodium propionate, i.e., ethanol COD equivalent: anhydrous sodium acetate COD equivalent: sodium propionate COD equivalent = 1:1:1), and the hydraulic retention time of the reactor was 24 h. The COD removal rate of the anaerobic digestion moving bed biofilm reactor was measured and the methanogenic performance was monitored. The results are shown in Table 1.

[0122] Example 8

[0123] The COD concentration of the reactor influent in Example 3 was changed to 3600 mg / L (including 576.92 mg / L of ethanol, 1538.48 mg / L of anhydrous sodium acetate, and 1025.64 mg / L of sodium propionate, i.e., ethanol COD equivalent: anhydrous sodium acetate COD equivalent: sodium propionate COD equivalent = 1:1:1), and the hydraulic retention time of the reactor was 24 h. The COD removal rate of the anaerobic digestion moving bed biofilm reactor was measured and the methanogenic performance was monitored. The results are shown in Table 1.

[0124] Example 9

[0125] The COD concentration of the reactor influent in Example 4 was changed to 3600 mg / L (including 576.92 mg / L of ethanol, 1538.48 mg / L of anhydrous sodium acetate, and 1025.64 mg / L of sodium propionate, i.e., ethanol COD equivalent: anhydrous sodium acetate COD equivalent: sodium propionate COD equivalent = 1:1:1), and the hydraulic retention time of the reactor was 24 h. The COD removal rate of the anaerobic digestion moving bed biofilm reactor was measured and the methanogenic performance was monitored. The results are shown in Table 1.

[0126] Example 10

[0127] The COD concentration of the reactor influent in Example 5 was changed to 3600 mg / L (including 576.92 mg / L of ethanol, 1538.48 mg / L of anhydrous sodium acetate, and 1025.64 mg / L of sodium propionate, i.e., ethanol COD equivalent: anhydrous sodium acetate COD equivalent: sodium propionate COD equivalent = 1:1:1), and the hydraulic retention time of the reactor was 24 h. The COD removal rate of the anaerobic digestion moving bed biofilm reactor was measured and the methanogenic performance was monitored. The results are shown in Table 1.

[0128] Comparative Example 1

[0129] The K1 carrier (K1 type suspended carrier packing) obtained directly from the market was added to the moving bed biofilm reactor for anaerobic digestion. The volume of the added K1 carrier accounted for 20% of the working volume of the reactor. The COD concentration of the reactor influent was 1800 mg / L (which included 288.46 mg / L of ethanol, 769.24 mg / L of anhydrous sodium acetate, and 512.82 mg / L of sodium propionate, i.e., ethanol COD equivalent: anhydrous sodium acetate COD equivalent: sodium propionate COD equivalent = 1:1:1). The hydraulic retention time of the reactor was 24 h. The COD removal rate of the moving bed biofilm reactor for anaerobic digestion was measured and the methanogenic performance was monitored. The results are shown in Table 1.

[0130] Comparative Example 2

[0131] The COD concentration of the reactor in Comparative Example 1 was changed to 3600 mg / L (including 576.92 mg / L of ethanol, 1538.48 mg / L of anhydrous sodium acetate, and 1025.64 mg / L of sodium propionate, i.e., ethanol COD equivalent: anhydrous sodium acetate COD equivalent: sodium propionate COD equivalent = 1:1:1), and the hydraulic retention time of the reactor was 24 h. The COD removal rate of the anaerobic digestion moving bed biofilm reactor was measured and the methanogenesis performance was monitored. The results are shown in Table 1.

[0132] Table 1. Summary of Reactor COD Removal Efficiency and Methanogenesis Performance in Examples 1-10 and Comparative Examples 1-2

[0133]

[0134]

[0135] As shown in Table 1, the operation examples 1-5 and 6-10, which added surface-conductive functional biological carriers to enhance anaerobic digestion, significantly improved the substrate degradation and utilization capacity (COD removal rate) under an influent environment with continuously increasing influent COD, compared to Comparative Examples 1 and 2, which directly added K1 carriers. Simultaneously, they also significantly improved the methanogenesis performance in anaerobic digestion. Specifically, the introduction of surface-modified functional biological carriers increased the methanogenesis rate and significantly shortened the methanogenesis lag period during anaerobic digestion, resulting in an increase in the final methane production volume and the proportion of methane in biogas. Therefore, the addition of surface-conductive functional biological carriers to enhance anaerobic digestion effectively improved the resource utilization and energy recovery capabilities of the substrate during anaerobic digestion.

[0136] Furthermore, compared to Comparative Example 2, in Examples 6-10, when the influent COD concentration further increases and the organic load is too high, the addition of functional biological carriers with surface conductive modification used to enhance anaerobic digestion can effectively improve the buffering capacity of the reactor, that is, maintain a higher COD removal rate and methanogenic capacity. Specifically, in Example 6 (conductive carrier containing only biochar), Example 7 (conductive carrier containing only conductive graphite), Example 8 (conductive carrier containing only iron oxide), Example 9 (conductive carrier composed of a mixture of activated carbon and iron oxide), and Example 10 (conductive carrier composed of a mixture of conductive graphite and iron oxide), compared to Comparative Example 2, their COD removal rates increased by 21.90%, 24.85%, 21.63%, 30.73%, and 27.79%, respectively, and their methane production was 1.73 times, 1.82 times, 1.79 times, 1.96 times, and 2.10 times that of Comparative Example 2, respectively.

[0137] Furthermore, compared to Examples 1-3, Examples 4-5 and Examples 9-10 compared to Examples 6-8 have further improved the COD removal rate and methanogenic capacity, and can further shorten the lag period of anaerobic digestion methanogenesis and increase its methanogenic rate.

[0138] Therefore, based on the above implementation results, it is believed that: 1) By introducing polyurethane adhesives, such as castor oil-based polyurethane adhesives, to modify the surface of polyethylene carriers, a functional biological carrier with surface conductive modification for enhancing anaerobic digestion can be obtained. Compared with directly adding polyethylene carriers, this can significantly improve anaerobic digestion performance, specifically manifested in improved COD removal rate and methanogenic capacity; 2) Carriers modified with a mixture of iron-based and carbon-based conductive materials can further improve anaerobic digestion performance compared with carriers modified with a single material.

[0139] 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 biological carrier used as a suspended packing material for anaerobic digestion of wastewater, comprising: Polyethylene biological carrier; A polyurethane adhesive layer laminated onto the surface of the polyethylene biocarrier; A conductive material functional layer laminated on the surface of a polyurethane adhesive layer; The polyurethane adhesive layer is prepared from raw materials including component a and component b; Component a includes castor oil; Component b includes at least one of polymeric MDI, TDI, MDI, HDI, IPDI, and PAPI; The volume ratio of component a to component b is 3.5~5.5:1; The method for preparing the biological carrier includes the following steps: A) The polyethylene biocarrier is placed in a polyurethane adhesive, stirred and mixed, and then removed to obtain an adhesive carrier substrate; B) The viscous carrier substrate is placed in a conductive material solid powder, stirred and mixed evenly, and then dried and cured to obtain a biological carrier.

2. The biological carrier according to claim 1, characterized in that, The polyethylene biological carrier includes K1 type suspended carrier packing, K2 type suspended carrier packing or K3 type suspended carrier packing.

3. The biological carrier according to claim 1, characterized in that, The thickness of the polyurethane adhesive layer is 0.04~0.3 mm.

4. The biological carrier according to claim 1, characterized in that, The conductive material of the conductive material functional layer includes at least one of carbon-based conductive materials and iron-based conductive materials; The carbon-based conductive material includes at least one of biochar, activated carbon, conductive graphite, graphene, carbon nanotubes, carbon cloth, carbon fiber, and carbon black. The iron-based conductive material includes at least one of zero-valent iron, iron(II,III) oxide, and iron(III) oxide.

5. The biological carrier according to claim 4, characterized in that, The conductive material is biochar; or the conductive material is conductive graphite; or the conductive material is iron(III) oxide; or the conductive material is obtained by mixing biochar and iron(III) oxide, wherein the mass ratio of biochar to iron(III) oxide is 0.7~1.3:1~1.5; or the conductive material is obtained by mixing conductive graphite and iron(III) oxide, wherein the mass ratio of conductive graphite to iron(III) oxide is 0.5~1.2:0.8~1.

3.

6. The biological carrier according to claim 1, characterized in that, The thickness of the conductive material functional layer is 0.01~0.3 mm.

7. The biological carrier according to claim 1, characterized in that, The mass ratio of the polyethylene biocarrier, the polyurethane adhesive layer, and the conductive material functional layer is 3~3.5:1~2.5:0.5~3.

8. The application of the biological carrier according to any one of claims 1 to 7 as a suspended packing material for anaerobic digestion treatment of wastewater.

Images