Aqueous polyurethane filler, process for its preparation and use

Abstract

The application discloses a kind of water-based polyurethane fillers, which is made of raw materials including the following components: polyol 80-100 parts by weight, isocyanate 35-50 parts by weight, hydrophilic cellulose 1-20 parts by weight, agarose 0.2-6 parts by weight, activated carbon 0.5-3 parts by weight, foaming agent 1-13 parts by weight, uniform foaming agent 0.5-1.5 parts by weight, gel catalyst 10-13 parts by weight. The application also discloses a preparation method of the water-based polyurethane filler and its application in wastewater treatment. The water-based polyurethane filler of the application has a large specific surface area, high treatment capacity, long service life, low sludge yield and high efficiency in treating wastewater.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical industry and environmental protection, and particularly relates to a water-based polyurethane filler, a preparation method and application thereof. BACKGROUND

[0002] The moving bed biofilm reactor (MBBR) is a new type of high-efficiency reactor between the activated sludge method and the fixed biofilm method, and its basic working principle is to add a certain proportion of suspended filler as a microbial growth carrier into an aeration tank, so that the sewage is purified by the action of microorganisms. The growing thick biofilm can be removed under the scouring action of water flow and gas, and is continuously renewed. Due to the cutting effect of the filler on aeration, the oxygen transfer efficiency in the reactor is greatly improved. The carrier has a large specific surface area, is suitable for microbial adsorption and growth, can efficiently degrade organic pollutants in the sewage, and the biofilm sludge age on the carrier is long, which is more suitable for the growth of nitrifying bacteria, and can significantly improve the nitrification denitrification effect.

[0003] In the practical application of the MBBR, the selection of the filler is particularly important, and the filler is required to have a large specific surface area, a rough surface, be beneficial to microbial attachment, and have a density slightly smaller than water (the density is equivalent to water when the biofilm is hung). In addition, it also needs to be wear-resistant and corrosion-resistant, and has high mechanical strength, so as to ensure the stability and economic efficiency of long-period operation.

[0004] The polyurethane filler is an excellent sewage treatment filler, has the advantages of controllable filler pore size and large specific surface area, is used for sewage upgrading and reconstruction, can effectively improve the sewage treatment load, solve the problem of site shortage, and has a good effect on the treatment of pollutants in the reactor to which the filler is added, so that the sewage can be discharged in accordance with the standard. However, the filler has a hydrophobic surface, which leads to a long biofilm formation time in the biochemical system, and the microbial adsorption is not firm and is easy to fall off. Therefore, it is of great significance to modify the MBBR filler to improve its hydrophilicity and biological affinity, so as to improve the purification efficiency of microorganisms on pollutants in the wastewater and the operation stability. SUMMARY

[0005] In view of the problems in the prior art, the purpose of the present application is to provide a water-based polyurethane filler, which can effectively remove biodegradable pollutants in the sewage by the MBBR technology. The water-based polyurethane filler provided by the present application can achieve the following purposes: (1) the filler has a controllable density range and a large specific surface area, and the pore structure is controllable; (2) the filler has good hydrophilicity, and can realize effective attachment of microorganisms, so that the start-up time of the reactor is short; (3) the filler has high mechanical strength, is wear-resistant and corrosion-resistant, and has a long service life; (4) the CODcr removal rate of the sewage treated by the filler is more than 70%, and the ammonia nitrogen removal rate is more than 95%.

[0006] To this end, the present application provides, in a first aspect, an aqueous polyurethane filler prepared from a raw material comprising 80-100 parts by weight of a polyol, 35-50 parts by weight of an isocyanate, 1-20 parts by weight of a hydrophilic cellulose, 0.2-6 parts by weight of agarose, 0.5-3 parts by weight of activated carbon, 1-13 parts by weight of a blowing agent, 0.5-1.5 parts by weight of a cell stabilizer, and 10-13 parts by weight of a gel catalyst.

[0007] In the present application, the aqueous polyurethane filler is generally prepared by mixing, foaming, and curing the raw material.

[0008] According to some embodiments of the present application, the aqueous polyurethane filler is prepared by mixing and reacting a raw material comprising 80-90 parts by weight of a polyol, 35-40 parts by weight of an isocyanate, 3-10 parts by weight of a hydrophilic cellulose, 1-3 parts by weight of agarose, 2-3 parts by weight of activated carbon, 1-5 parts by weight of a blowing agent, 0.5-1.5 parts by weight of a cell stabilizer, and 10-13 parts by weight of a gel catalyst.

[0009] According to some embodiments of the present application, the hydrophilic cellulose is selected from at least one of hydroxyethyl cellulose and hydroxypropyl methylcellulose.

[0010] According to some embodiments of the present application, the polyol is selected from at least one of a polyether polyol and a polyester polyol.

[0011] According to some embodiments of the present application, the polyether polyol has a functionality of 2-3.

[0012] According to some embodiments of the present application, the polyether polyol has an average molecular weight of 1500-4500.

[0013] According to some embodiments of the present application, the polyether polyol is at least one of a polyether diol and a polyether triol.

[0014] According to some embodiments of the present application, the polyester polyol has an average molecular weight of 2000-4000.

[0015] According to some embodiments of the present application, the polyester polyol has a functionality of 2-3.

[0016] According to some embodiments of the present application, the isocyanate is selected from at least one of diphenylmethane diisocyanate, toluene diisocyanate, and methylcyclohexyl diisocyanate.

[0017] According to some embodiments of the present application, the blowing agent is at least one of water and dichloromethane.

[0018] According to the present application, the cell stabilizer can use the commonly used or known cell stabilizer in the art for increasing the solubility of each component, stabilizing the foam and adjusting the cell, and in some preferred embodiments, the cell stabilizer is selected from at least one of methyl silicone oil, dimethyl silicone oil and hydroxyl silicone oil. In some preferred embodiments, the cell stabilizer is methyl silicone oil 201.

[0019] According to the present application, the gel catalyst is a catalyst for promoting the gel reaction of the polyurethane foam in the later stage, and in some preferred embodiments, the gel catalyst is at least one of triethylenediamine, stannous octoate and dibutyltin dilaurate.

[0020] According to some embodiments of the present application, the specific surface area of the water-based polyurethane filler is greater than 2000m 2 / m 3 , the porosity is not less than 90%, and the hydrophilic angle is less than 75°.

[0021] According to some embodiments of the present application, the relative density of the water-based polyurethane filler is 1.10-1.25kg / m 3 .

[0022] The second aspect of the present application provides a preparation method of the water-based polyurethane filler as described in the first aspect of the present application, which comprises the following steps:

[0023] (1) First mixing polyol, hydrophilic cellulose, agarose, activated carbon, foaming agent, cell stabilizer and gel catalyst to obtain a first mixture;

[0024] (2) Second mixing the obtained first mixture with isocyanate and standing to obtain a second mixture;

[0025] (3) Foaming the obtained second mixture and then curing to obtain the water-based polyurethane filler.

[0026] According to some embodiments of the present application, step (3) further comprises cutting the product obtained after curing so that the water-based polyurethane filler is a regular hexahedral particle, and the side length of the regular hexahedron is 1-5cm.

[0027] According to some embodiments of the present application, the temperature of the first mixing is 20-35℃.

[0028] According to some embodiments of the present application, the first mixing is stirring at a rotation speed of 1000-1500rpm, and the stirring time is 5-10min.

[0029] According to some embodiments of the present application, the second mixing is carried out at room temperature.

[0030] According to some embodiments of the present application, the second mixing is performed by stirring at a speed of 1500-2200 rpm, and the stirring time is 2-4 min.

[0031] According to some embodiments of the present application, the standing time is 5-10 min.

[0032] According to some embodiments of the present application, the foaming time is 30-60 min.

[0033] According to some embodiments of the present application, the foaming temperature is 15-35℃.

[0034] According to some embodiments of the present application, the solidification is performed at 20-40℃.

[0035] According to some embodiments of the present application, the solidification time is 40-72 h.

[0036] The third aspect of the present application provides an application of the waterborne polyurethane filler as described in the first aspect of the present application or prepared by the method as described in the second aspect of the present application in sewage treatment.

[0037] According to some embodiments of the present application, the application comprises the following steps:

[0038] a) adding the waterborne polyurethane filler as described in the present application to a biological aerated filter;

[0039] b) introducing inoculated sludge into the biological aerated filter to which the filler is added in step a);

[0040] c) introducing sewage to be treated into the biological aerated filter inoculated with sludge in step b), and completing the filler biofilm formation and start-up process in 7-14 days, and then performing sewage treatment.

[0041] According to some embodiments of the present application, in step a), the volume of the waterborne polyurethane filler added accounts for 10%-50% of the volume of the biological aerated filter. In some embodiments, the volume of the waterborne polyurethane filler added accounts for 15%-30% of the volume of the biological aerated filter, for example 15%, 20%, 25%, 30% and any value therebetween.

[0042] According to some embodiments of the present application, in step b), the initial concentration of the inoculated sludge introduced into the biological aerated filter is 1-2 g / L.

[0043] According to some embodiments of the present application, in step c), during the biofilm formation and start-up process, the final sludge concentration in the biological aerated filter is reduced to below 0.1 g / L and the sewage treatment is performed at this concentration. In some embodiments, during the biofilm formation and start-up process, the final sludge concentration in the biological aerated filter is reduced to 0.05-0.1 g / L.

[0044] According to some embodiments of the present application, the start-up of biofilm in step c) starts the process of filling biofilm under low COD load conditions, and gradually increases to high COD load for the start-up of filling biofilm.

[0045] According to some embodiments of the present application, the concentration of dissolved oxygen in the biological aeration tank in the sewage treatment is maintained at 2-6 g / L. In some preferred embodiments, the concentration of dissolved oxygen in the biological aeration tank in the sewage treatment is maintained at 2-4 g / L, such as 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L and any value therebetween.

[0046] According to some embodiments of the present application, the pH in the biological aeration tank in the sewage treatment process in step c) is 6-9.

[0047] According to some embodiments of the present application, the temperature in the biological aeration tank in the sewage treatment is 23-30℃.

[0048] According to some embodiments of the present application, the sewage flow is kept constant during the sewage treatment process.

[0049] According to some embodiments of the present application, the sewage is chemical wastewater, such as organic wastewater.

[0050] According to some embodiments of the present application, the sewage is ammonia-nitrogen wastewater.

[0051] In the present application, the "average molecular weight" index is the average molecular weight.

[0052] In the present application, the "functional degree" is the hydroxyl functional degree.

[0053] Compared with the prior art, the present application has the following advantages:

[0054] 1) The water-based polyurethane filler of the present application adds cellulose-based hydrophilic powder, activated carbon and agarose, wherein the addition of cellulose-based hydrophilic powder improves the hydrophilicity of the polyurethane filler, makes it sink quickly when encountering water, and can be completely fluidized in a short time after the filler is put in; the addition of activated carbon improves the adsorption capacity of the filler to pollutants, prolongs the residence time of pollutants on the filler, and improves the sewage treatment efficiency; the addition of agarose can improve the biological affinity of the polyurethane filler, which is more conducive to the growth of microorganisms on the surface of the filler and accelerates the biofilm formation speed.

[0055] 2) The hydrophilic polyurethane filler of the present application has large specific surface area, high treatment capacity, long service life, low sludge yield and high sewage treatment efficiency. DETAILED DESCRIPTION

[0056] In order to make the present application more readily understood, reference will be made to the following examples, it being expressly understood that the following examples are only by way of exemplification and should not be considered as limiting the scope of the application. Unless otherwise indicated, the conditions of the examples are conventional or manufacturer's recommended conditions. Where the manufacturer of reagents or instruments is not indicated, it should be assumed to be an available conventional product or reagent obtained either from a commercial vendor or by conventional or published methods.

[0057] Example 1

[0058] The foaming agent used in this example is dichloromethane, the polyol is polyether polyol (polypropylene glycol, functionality 2, average molecular weight 4000), the isocyanate is methylcyclohexyl diisocyanate, the cell stabilizer is methyl silicone oil 201, the gel catalyst is triethylenediamine, the hydrophilic cellulose is hydroxyethyl cellulose, and the activated carbon and agarose.

[0059] The specific preparation method of the waterborne polyurethane filler is as follows:

[0060] (1) At room temperature, 80 parts of polyether polyol, 3 parts of foaming agent, 1 part of cell stabilizer, 11 parts of gel catalyst, 5 parts of hydrophilic cellulose powder, 2 parts of activated carbon powder and 1 part of agarose are reacted at a temperature of 25±2°C and a rotation speed of 1200 rpm for 8 minutes to obtain a mixed liquid;

[0061] (2) 38 parts of methylcyclohexyl diisocyanate are added to the obtained mixed liquid, and stirred at a stirring speed of 1800 rpm for 4 minutes, and then left to stand for 10 minutes;

[0062] (3) The solution after standing is poured into a foaming box, foamed at 25°C for 40 minutes, and then placed in a vacuum thermostat for normal temperature curing for 40 hours to obtain a foaming body. The foaming body is mechanically cut to obtain a waterborne polyurethane filler, which is a regular hexahedron with a side length of 2 cm.

[0063] The specific preparation method of the waterborne polyurethane filler is as follows: 2 3 The specific preparation method of the waterborne polyurethane filler is as follows: 3

[0064] ​​Application evaluation of the waterborne polyurethane filler: the prepared waterborne polyurethane filler was put into a biological aerated tank, the waterborne polyurethane filler accounted for 25% of the volume of the biological aerated tank, inoculated sludge was introduced into the biological aerated tank, the initial inoculated sludge concentration was 1 g / L, and the filler was started for sewage treatment after 10 days of biofilm formation. The concentration of dissolved oxygen in the biological aerated tank was maintained at 2 g / L, the pH in the biological aerated tank during sewage treatment was 8, and the temperature in the biological aerated tank was 26°C. The sludge concentration in the biological aerated tank under normal operation conditions after the start was 0.05 g / L.

[0065] After the sewage treatment, the CODcr removal rate was 78%, and the NH3-N removal rate was 96%.

[0066] Example 2

[0067] The specific preparation method of the waterborne polyurethane filler was the same as that in Example 1, except that the prepared foam was mechanically cut, and finally the waterborne polyurethane filler with a regular hexahedron shape and a side length of 4 cm was obtained. The specific surface area of the prepared waterborne polyurethane filler was greater than 2000 m 2 / m 3 , the porosity was not less than 90%, the hydrophilic angle was less than 72°, and the relative density was in the range of 1.10-1.25 kg / m 3 .

[0068] Application evaluation of the waterborne polyurethane filler: the prepared waterborne polyurethane filler was put into a biological aerated tank, the waterborne polyurethane filler accounted for 10% of the volume of the biological aerated tank, inoculated sludge was introduced into the biological aerated tank, the initial inoculated sludge concentration was 1 g / L, and the filler was started for sewage treatment after 14 days of biofilm formation. The concentration of dissolved oxygen in the biological aerated tank was maintained at 2 g / L, the sludge concentration in the biological aerated tank under normal operation conditions after the start was 0.08 g / L. The pH in the biological aerated tank during sewage treatment was 6.5, and the temperature in the biological aerated tank was 23°C.

[0069] After the sewage treatment, the CODcr removal rate was 75%, and the NH3-N removal rate was 95%.

[0070] Example 3

[0071] The specific preparation method of the waterborne polyurethane filler was the same as that in Example 2, except that the raw material dosage was 80 parts of polyether polyol, 3 parts of foaming agent, 1 part of foam stabilizer, 11 parts of gel catalyst, 3 parts of hydrophilic cellulose powder, 3 parts of activated carbon powder, and 2 parts of agarose and 38 parts of isocyanate. The specific surface area of the prepared waterborne polyurethane filler was greater than 2000 m 2 / m 3 , the porosity was not less than 90%, the hydrophilic angle was less than 72°, and the relative density was in the range of 1.10-1.25 kg / m 3 .

[0072] The application evaluation of the waterborne polyurethane filler is as follows: the prepared waterborne polyurethane filler is put into a biological aerated tank, the proportion of the waterborne polyurethane filler in the volume of the biological aerated tank is 30%, inoculated sludge is introduced into the biological aerated tank, the initial concentration of the inoculated sludge is 2 g / L, the start-up of the filler biofilm formation is completed in 7 days, the concentration of dissolved oxygen in the biological aerated tank is kept at 3 g / L, the pH in the biological aerated tank during the sewage treatment process is 7, and the temperature in the biological aerated tank is 26°C. The sludge concentration in the biological aerated tank under the normal running condition after the start-up is completed is 0.03 g / L.

[0073] The results show that the removal rate of CODcr of the treated sewage is 82%, and the removal rate of NH3-N is 98%.

[0074] Example 4

[0075] The specific preparation method of the waterborne polyurethane filler is the same as that in Example 2, except that the dosages of the raw materials are 80 parts of polyether polyol, 3 parts of foaming agent, 1 part of foam stabilizer, 11 parts of gel catalyst, 3 parts of hydrophilic cellulose powder, 2 parts of activated carbon powder, 3 parts of agarose and 38 parts of methylcyclohexyl diisocyanate. The specific surface area of the prepared waterborne polyurethane filler is greater than 2000 m 2 / m 3 , the porosity is not less than 90%, the hydrophilic angle is less than 72°, and the relative density is in the range of 1.10-1.25 kg / m 3 .

[0076] The application evaluation of the waterborne polyurethane filler is as follows: the prepared waterborne polyurethane filler is put into a biological aerated tank, the proportion of the waterborne polyurethane filler in the volume of the biological aerated tank is 15%, inoculated sludge is introduced into the biological aerated tank, the initial concentration of the inoculated sludge is 1 g / L, the start-up of the filler biofilm formation is completed in 10 days, the concentration of dissolved oxygen in the biological aerated tank is kept at 4 g / L, the pH in the biological aerated tank during the sewage treatment process is 6.5, and the temperature in the biological aerated tank is 30°C. The sludge concentration in the biological aerated tank under the normal running condition after the start-up is completed is 0.05 g / L. The results show that the removal rate of CODcr of the treated sewage is 80%, and the removal rate of NH3-N is 97%.

[0077] Example 5

[0078] The specific preparation method of the waterborne polyurethane filler is the same as that in Example 2, except that the dosages of the raw materials are 80 parts of polyether polyol, 3 parts of foaming agent, 1 part of foam stabilizer, 11 parts of gel catalyst, 1 part of hydrophilic cellulose powder, 1 part of activated carbon powder, 6 parts of agarose and 38 parts of isocyanate. The specific surface area of the prepared waterborne polyurethane filler is greater than 2000 m 2 / m 3, porosity is not less than 90%, hydrophilic angle is less than 75°, relative density is in the range of 1.10-1.25 kg / m 3 .

[0079] Application evaluation of the waterborne polyurethane filler: the prepared waterborne polyurethane filler is put into a biological aerated tank, the proportion of the waterborne polyurethane filler in the volume of the biological aerated tank is 15%, inoculated sludge is introduced into the biological aerated tank, the initial concentration of the inoculated sludge is 2 g / L, the start-up of the biofilm on the filler is completed in 7 days, the concentration of dissolved oxygen in the biological aerated tank is maintained at 4 g / L, the pH in the biological aerated tank during the sewage treatment process is 7; the temperature in the biological aerated tank is 25°C. The concentration of the sludge in the biological aerated tank under the normal operation condition after the start-up is completed is 0.05 g / L. After the sewage is treated, the removal rate of CODcr is 77%, and the removal rate of NH3-N is 97%.

[0080] Comparative Example 1

[0081] The specific preparation method of the waterborne polyurethane filler is the same as that in Example 1, except that the dosages of the raw materials are 80 parts of polyether polyol, 3 parts of foaming agent, 1 part of foam stabilizer, 11 parts of gel catalyst, 2 parts of hydrophilic cellulose powder, 6 parts of activated carbon and 38 parts of isocyanate.

[0082] Application evaluation of the waterborne polyurethane filler: the prepared waterborne polyurethane filler is put into a biological aerated tank, the proportion of the waterborne polyurethane filler in the volume of the biological aerated tank is 30%, inoculated sludge is introduced into the biological aerated tank, the initial concentration of the inoculated sludge is 2 g / L, the start-up of the biofilm on the filler is completed in 20 days, the concentration of dissolved oxygen in the biological aerated tank is maintained at 3 g / L, the pH in the biological aerated tank during the sewage treatment process is 7; the temperature in the biological aerated tank is 25°C. The concentration of the sludge in the biological aerated tank under the normal operation condition after the start-up is completed is 0.1 g / L.

[0083] After the sewage is treated, the removal rate of CODcr is 73%, and the removal rate of NH3-N is 93%.

[0084] Comparative Example 2

[0085] The specific preparation method of the waterborne polyurethane filler is the same as that in Example 1, except that the dosages of the raw materials are 80 parts of polyether polyol, 3 parts of foaming agent, 1 part of foam stabilizer, 11 parts of gel catalyst, 2 parts of agarose and 6 parts of activated carbon and 38 parts of methylcyclohexyl diisocyanate.

[0086] Evaluation of the application of the waterborne polyurethane filler: the prepared waterborne polyurethane filler is put into a biological aerated tank, the proportion of the waterborne polyurethane filler in the volume of the biological aerated tank is 30%, inoculated sludge is introduced into the biological aerated tank, the initial concentration of the inoculated sludge is 2 g / L, the biofilm formation and start-up of the filler are completed in 22 days, the concentration of dissolved oxygen in the biological aerated tank is maintained at 3 g / L, the pH in the sewage treatment process is 7, and the temperature in the biological aerated tank is 25℃. The concentration of sludge in the biological aerated tank under the conditions of start-up completion and normal operation is 0.13 g / L.

[0087] After the treatment, the removal rate of CODcr is 70%, and the removal rate of NH3-N is 92%.

[0088] It should be noted that the above-described embodiments are only used to explain the present application and do not constitute any limitation on the present application. The present application is described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than limiting words. The present application can be modified as specified within the scope of the claims of the present application, and the present application can be revised without departing from the scope and spirit of the present application. Although the present application described therein relates to specific methods, materials and embodiments, it does not mean that the present application is limited to the specific examples disclosed therein, on the contrary, the present application can be extended to all other methods and applications with the same function.

Claims

1. An aqueous polyurethane filler prepared from a raw material consisting of the following components: polyol 80-100 parts by weight, isocyanate 35-50 parts by weight, hydrophilic cellulose 1-20 parts by weight, agarose 0.2-6 parts by weight, activated carbon 0.5-3 parts by weight, foaming agent 1-13 parts by weight, uniform foaming agent 0.5-1.5 parts by weight, and gel catalyst 10-13 parts by weight; the hydrophilic cellulose is at least one selected from hydroxyethyl cellulose and hydroxypropyl methyl cellulose; the foaming agent is dichloromethane; and the uniform foaming agent is at least one selected from methyl silicone oil, dimethyl silicone oil and hydroxyl silicone oil. The preparation method of the aqueous polyurethane filler comprises the following steps: (1) first mixing polyol, hydrophilic cellulose, agarose, activated carbon, foaming agent, uniform foaming agent and gel catalyst to obtain a first mixture; (2) second mixing the obtained first mixture with isocyanate and standing to obtain a second mixture; (3) foaming the obtained second mixture and then curing to obtain the aqueous polyurethane filler.

2. The aqueous polyurethane filler according to claim 1, characterized in that, The raw material of the aqueous polyurethane filler consists of the following components: polyol 80-90 parts by weight, isocyanate 35-40 parts by weight, hydrophilic cellulose 3-10 parts by weight, agarose 1-3 parts by weight, activated carbon 2-3 parts by weight, foaming agent 1-5 parts by weight, uniform foaming agent 0.5-1.5 parts by weight, and gel catalyst 10-13 parts by weight.

3. The aqueous polyurethane filler of claim 1, wherein, The polyol is at least one selected from polyether polyol and polyester polyol; and / or the isocyanate is at least one selected from diphenylmethane diisocyanate, toluene diisocyanate and methylcyclohexyl diisocyanate.

4. The aqueous polyurethane filler of claim 3, wherein, The polyether polyol has a functionality of 2-3 and an average molecular weight of 1500-4500; and / or the polyester polyol has an average molecular weight of 2000-4000 and a functionality of 2-3.

5. The aqueous polyurethane filler of claim 4, wherein, The polyether polyol is at least one selected from polyether diol and polyether triol.

6. The aqueous polyurethane filler according to any one of claims 1 to 5, characterized in that, The gel catalyst is at least one selected from triethylenediamine, stannous octoate and dibutyltin dilaurate.

7. The aqueous polyurethane filler according to any one of claims 1 to 5, characterized in that, The specific surface area of the aqueous polyurethane filler is greater than 2000 m 2 / m 3 , the porosity is not less than 90%, and the hydrophilic angle is less than 75°.

8. The aqueous polyurethane filler according to claim 7, characterized in that, The relative density of the aqueous polyurethane filler is 1.10-1.25 kg / m 3 .

9. A preparation method of the aqueous polyurethane filler according to any one of claims 1-8, comprising the following steps: (1) first mixing polyol, hydrophilic cellulose, agarose, activated carbon, foaming agent, uniform foaming agent and gel catalyst to obtain a first mixture; (2) second mixing the obtained first mixture with isocyanate and standing to obtain a second mixture; (3) foaming the obtained second mixture and then curing to obtain the aqueous polyurethane filler.

10. The method of claim 9, wherein, Step (3) further comprises cutting the product obtained after curing so that the aqueous polyurethane filler is a regular hexahedral particle, and the side length of the regular hexahedron is 1-5 cm.

11. The preparation method according to claim 9, characterized in that, The temperature of the first mixing is 20-35°C, and / or the first mixing is stirring at a rotation speed of 1000-1500 rpm for 5-10 min; and / or the second mixing is carried out at 20-35℃; and / or the second mixing is carried out by stirring at a rotation speed of 1500-2200 rpm, the stirring time is 2-4 min, and / or the standing time is 5-10 min.

12. The production method according to any one of claims 9 to 11, characterized by, In step (3), the foaming time is 30-60 min, and the foaming temperature is 15-35℃; and / or the solidification is carried out at 20-40℃, and the solidification time is 40-72 h.

13. Use of the aqueous polyurethane filler according to any one of claims 1-8 or prepared by the preparation method according to any one of claims 9-12 in sewage treatment.

14. Use according to claim 13, characterized in that, The use comprises the following steps: a) adding the aqueous polyurethane filler according to any one of claims 1-8 or prepared by the preparation method according to any one of claims 9-12 into a biological aerated filter; b) introducing inoculated sludge into the biological aerated filter to which the filler is added in step a); c) introducing sewage to be treated into the biological aerated filter inoculated with sludge in step b), and completing the filler biofilm formation start-up process in 7-14 days, and then carrying out sewage treatment.

15. The use according to claim 13, characterized in that, In step a), the volume of the added aqueous polyurethane filler accounts for 10%-50% of the volume of the biological aerated filter; and / or in step b), the initial concentration of the inoculated sludge introduced into the biological aerated filter is 1-2 g / L; and / or in step c), the final sludge concentration in the biological aerated filter during the biofilm formation start-up process is reduced to below 0.1 g / L, and the sewage treatment is carried out while maintaining this concentration.

16. The use according to any one of claims 13 to 15, characterized in that, In the sewage treatment, the concentration of dissolved oxygen in the biological aerated filter is maintained at 2-6 g / L, and / or in step c), the pH in the biological aerated filter during the sewage treatment process is 6-9; and / or the temperature in the biological aerated filter is 23-30℃.