A medical stone-based composite filler, its preparation method and application

Abstract

The present invention belongs to the field of sewage treatment technology, and in particular relates to a medical stone-based composite filler, its preparation method, and application. The present invention provides a medical stone-based composite filler comprising a medical stone substrate and a coating located within the pores and surface of the medical stone substrate; the medical stone substrate comprises medical stone, sulfur, activated carbon, iron powder, and polyethylene; and the coating comprises microcrystalline cellulose, calcium carbonate, polyhydroxy fatty acid, polyvinyl alcohol, sodium lauryl sulfate, and epoxy resin. The medical stone-based composite filler provided by the present invention exhibits excellent denitrification performance when used as a sulfur autotrophic denitrification filler.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and in particular relates to a medical stone-based composite filler and a preparation method and application thereof. Background Art

[0002] As denitrification standards continue to rise, traditional denitrification methods (physicochemical denitrification methods) struggle to meet these high standards. Sulfur autotrophic denitrification uses reduced sulfur as an electron donor under the action of autotrophic Thiobacillus denitrificans. This process requires no added organic matter and offers low operating costs and excellent denitrification results. Currently, sulfur autotrophic denitrification technology is increasingly being used for deep denitrification of low carbon-to-nitrogen ratios, such as in urban tailwater.

[0003] Sulfur autotrophic denitrification fillers are crucial to the success of sulfur autotrophic denitrification. Currently, sulfur is typically used as a filler to provide the sulfur source required for the reaction, with limestone added to balance the acid produced by elemental sulfur autotrophic denitrification. However, due to its poor solubility in water, sulfur requires "passive dissolution" by microorganisms before it can be utilized by sulfur autotrophic bacteria, which, to a certain extent, limits the denitrification efficiency of sulfur autotrophic denitrification. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a medical stone-based composite filler and a preparation method and application thereof. The medical stone-based composite filler provided by the present invention has a good denitrification effect when used as a sulfur autotrophic denitrification filler.

[0005] In order to achieve the above objectives, the present invention provides the following technical solutions:

[0006] The present invention provides a medical stone-based composite filler, comprising a medical stone matrix and a coating located in the pores and surface of the medical stone matrix; the components of the medical stone matrix include medical stone, sulfur, activated carbon, iron powder and polyethylene;

[0007] The components of the coating include microcrystalline cellulose, calcium carbonate, polyhydroxy fatty acid, polyvinyl alcohol, sodium lauryl sulfate and epoxy resin.

[0008] Preferably, the particle sizes of the medical stone, sulfur and activated carbon are independently 200-400 meshes.

[0009] Preferably, in parts by mass, the medical stone matrix comprises 30 to 60 parts of medical stone; 20 to 60 parts of sulfur; 20 to 40 parts of activated carbon; 5 to 20 parts of iron powder; and 5 to 10 parts of polyethylene.

[0010] Preferably, the coating comprises, by mass, 30 to 50 parts of microcrystalline cellulose; 10 to 20 parts of calcium carbonate; 3 to 8 parts of polyhydroxy fatty acid; 5 to 15 parts of polyvinyl alcohol; 4 to 9 parts of sodium lauryl sulfate; and 10 to 20 parts of epoxy resin.

[0011] Preferably, the particle sizes of the medical stone, sulfur and activated carbon are independently 200-400 meshes; and the particle sizes of the microcrystalline cellulose and calcium carbonate powder are independently 100-200 meshes.

[0012] Preferably, the coating has a thickness of 0.5 to 1 cm.

[0013] The present invention also provides a method for preparing the above-mentioned medical stone-based composite filler, which is characterized by comprising the following steps:

[0014] Firstly mixing medical stone, sulfur, activated carbon, iron powder and polyethylene, and granulating the obtained medical stone-based mixture to obtain a medical stone matrix;

[0015] secondly mixing the microcrystalline cellulose, calcium carbonate, polyhydroxy fatty acid, polyvinyl alcohol, sodium lauryl sulfate and epoxy resin to obtain a coating mixture solution;

[0016] The coating mixture solution and the medical stone matrix are mixed for the third time under alkaline conditions, and then heated, coated and aged in sequence to obtain the medical stone-based composite filler.

[0017] Preferably, the heating coating is a water bath heating coating; the temperature of the water bath heating coating is 70 to 90° C., and the time is 1 to 2 hours.

[0018] Preferably, the aging is heating aging, and the temperature of the heating aging is 70-90° C. and the time is 1.5-2.5 hours.

[0019] The present invention also provides the use of the medical stone-based composite filler or the medical stone-based composite filler prepared by the above-mentioned preparation method in sewage treatment.

[0020] The present invention provides a medical stone-based composite filler comprising a medical stone matrix and a coating located in the pores and on the surface of the medical stone matrix. The medical stone matrix comprises medical stone, sulfur, activated carbon, iron powder, and polyethylene; and the coating comprises microcrystalline cellulose, calcium carbonate, polyhydroxy fatty acid, polyvinyl alcohol, sodium lauryl sulfate, and epoxy resin. In the present invention, the trace elements (Al, Fe, and Ca) dissolved from the medical stone in the medical stone matrix not only enhance microbial activity, promote bioaggregation, and increase biomass, but also reduce redox potential, regulate pH fluctuations during sulfur autotrophic denitrification, and create a favorable living environment for microorganisms, thereby enhancing the denitrification efficiency of microorganisms for nitrogenous pollutants. The iron powder in the medical stone matrix can increase biological activity and promote synergistic denitrification. The activated carbon can make the filler interior loose and porous, resulting in a large specific surface area, good adsorption performance, and large adsorption capacity, thereby effectively enhancing the adsorption of nitrogenous pollutants in wastewater and providing a foundation for denitrification. At the same time, the microcrystalline cellulose in the medical stone matrix can slowly release the carbon source, and the sulfur provides an electron donor for sulfur autotrophic denitrification. Therefore, the reaction does not require the addition of additional organic sulfur and carbon sources. In addition, because the coating dissolves various trace elements such as Ga, Fe, and Al in the filler matrix, and sodium dodecyl sulfate acts as a solid surfactant to enhance its activity, the enrichment of microorganisms increases, greatly enhancing microbial activity and significantly increasing their utilization of sulfur, carbon, and nutrients. It can also improve the denitrification effect of microorganisms on nitrogen-containing pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a diagram showing the effect of sulfur autotrophic denitrification in Example 1;

[0022] Figure 2 This is a diagram showing the effect of sulfur autotrophic denitrification in Example 2;

[0023] Figure 3 This is a diagram showing the effect of sulfur autotrophic denitrification in Example 3. DETAILED DESCRIPTION

[0024] The present invention provides a medical stone-based composite filler, comprising a medical stone matrix and a coating located in the pores and surface of the medical stone matrix; the components of the medical stone matrix include medical stone, sulfur, activated carbon, iron powder and polyethylene;

[0025] The components of the coating include microcrystalline cellulose, calcium carbonate, polyhydroxy fatty acid, polyvinyl alcohol, sodium lauryl sulfate and epoxy resin.

[0026] In the present invention, unless otherwise specified, the components are commercially available products well known to those skilled in the art.

[0027] In the present invention, the specific surface area of the medical stone-based composite filler is preferably 1500 to 3000 m2 / g, more preferably 2000 to 2800 m 2 / g, the porosity of the medical stone-based composite filler is preferably 40-60%, more preferably 45-55%.

[0028] In the present invention, the medical stone-based composite filler comprises a medical stone matrix. In the present invention, the components of the medical stone matrix include medical stone, sulfur, activated carbon, iron powder and polyethylene.

[0029] In the present invention, in parts by mass, the medical stone matrix preferably comprises 30 to 60 parts of medical stones, more preferably 40 to 50 parts. In the present invention, the porosity of the medical stone is preferably 25 to 35%, more preferably 30%. In the present invention, the particle diameter of the medical stone is preferably 200 to 400 orders, more preferably 300 orders. In the present invention, the trace elements (Al, Fe, Ca) dissolved in the medical stone matrix can not only improve microbial activity, strengthen biological aggregation and increase biomass, but also can reduce redox potential, thereby creating a good living environment for microorganisms.

[0030] In the present invention, the medical stone matrix preferably includes 20 to 60 parts by mass of sulfur, more preferably 30 to 50 parts. The sulfur preferably has a particle size of 200 to 400 mesh, more preferably 300 mesh. In the present invention, the sulfur can be used as a sulfur source by Thiobacillus denitrificans to initiate sulfur autotrophic denitrification. Furthermore, the sulfur and medical stone activated carbon together form the filler matrix skeleton, supporting the entire filler.

[0031] In the present invention, the medical stone matrix preferably includes 20 to 40 parts by mass of activated carbon, more preferably 25 to 30 parts. In the present invention, the particle size of the activated carbon is preferably 200 to 400 mesh, more preferably 300 mesh. In the present invention, the specific surface area of the activated carbon is preferably 1000 to 2000 m 2 / g, more preferably 1500 to 1800 m 2 In the present invention, the activated carbon can make the interior of the filler loose and porous, with a large specific surface area, good adsorption performance and large adsorption capacity.

[0032] In the present invention, the medical stone matrix preferably includes 5 to 20 parts by mass of iron powder, more preferably 10 to 15 parts. In the present invention, the iron powder preferably has a particle size of 400 to 600 mesh, more preferably 450 to 550 mesh. In the present invention, the iron element can increase biological activity, promote denitrification synergy, and promote microbial growth.

[0033] In the present invention, the medical stone matrix preferably includes 5 to 10 parts by weight of polyethylene, more preferably 6 to 8 parts. In the present invention, the polyethylene is preferably high-density polyethylene, and the weight-average molecular weight of the high-density polyethylene is preferably 20,000 to 30,000, more preferably 25,000 to 30,000. In the present invention, the polyethylene can provide toughness, strength, and plasticity to the filler.

[0034] In the present invention, the medical stone-based composite filler comprises a coating located in the pores and surface of the medical stone matrix. In the present invention, the thickness of the coating is preferably 0.5 to 1 cm, more preferably 0.6 to 0.8 cm.

[0035] In the present invention, the components of the coating include microcrystalline cellulose, calcium carbonate, polyhydroxy fatty acid, polyvinyl alcohol, sodium lauryl sulfate and epoxy resin.

[0036] In the present invention, the components of the coating preferably include 30 to 50 parts of microcrystalline cellulose, more preferably 40 to 45 parts, by mass. In the present invention, the particle size of the microcrystalline cellulose is preferably 100 to 300 mesh, more preferably 200 to 250 mesh. In the present invention, the selected microcrystalline cellulose is preferably derived from wood cellulose, bamboo cellulose, wheat cellulose, corn straw cellulose, corn cob cellulose or sugarcane bagasse cellulose. In the present invention, the microcrystalline cellulose can provide a carbon source for sulfur autotrophic denitrification. In the present invention, the microcrystalline cellulose is completely biodegradable, so the filler after use can be re-coated and reused.

[0037] In the present invention, the coating preferably comprises 10 to 20 parts by mass of calcium carbonate, more preferably 15 parts by mass. In the present invention, the particle size of the calcium carbonate is preferably 100 to 200 mesh, more preferably 120 to 180 mesh. In the present invention, the calcium carbonate acts as a buffer to resist the influence of adverse external pH.

[0038] In the present invention, the coating preferably comprises 3 to 8 parts by weight of a polyhydroxy fatty acid, more preferably 5 parts. In the present invention, the polyhydroxy fatty acid preferably comprises one or more of hydroxybutyric acid, hydroxyvaleric acid, and hydroxycaproic acid, with hydroxybutyric acid being more preferred. In the present invention, the polyhydroxy fatty acid can enhance the sustained-release properties of the filler, slowly releasing the carbon and sulfur sources for utilization by microorganisms.

[0039] In the present invention, the coating preferably comprises 5 to 15 parts by weight of polyvinyl alcohol, more preferably 10 parts. In the present invention, the weight-average molecular weight of the polyvinyl alcohol is preferably 16,000 to 20,000, more preferably 17,000 to 19,000. In the present invention, the polyvinyl alcohol acts as a toughening agent, reducing filler brittleness, increasing filler toughness, improving filler strength, and enhancing the adhesion between the coating and the filler substrate.

[0040] In the present invention, the coating preferably comprises 4 to 9 parts by mass of sodium lauryl sulfonate, more preferably 7 to 8 parts by mass. In the present invention, sodium lauryl sulfonate is a synergist that increases the activity of microcrystalline cellulose, enhances biodegradability, and improves filler effect.

[0041] In the present invention, the coating composition preferably includes 10 to 20 parts by mass of epoxy resin, more preferably 15 to 18 parts. In the present invention, the epoxy value of the epoxy resin is preferably 0.51 to 0.54 Eq / 100 g, more preferably 0.52 to 0.53 Eq / 100 g. In the present invention, the epoxy resin serves to bond the medical stone matrix and other components in the coating mixture.

[0042] The present invention also provides a method for preparing the above-mentioned medical stone-based composite filler, comprising the following steps:

[0043] Firstly mixing medical stone, sulfur, activated carbon, iron powder and polyethylene, and granulating the obtained medical stone-based mixture to obtain a medical stone matrix;

[0044] secondly mixing the microcrystalline cellulose, calcium carbonate, polyhydroxy fatty acid, polyvinyl alcohol, sodium lauryl sulfate and epoxy resin to obtain a coating mixture solution;

[0045] The coating mixture solution and the medical stone matrix are mixed for the third time under alkaline conditions, and then heated, coated and aged in sequence to obtain the medical stone-based composite filler.

[0046] The invention first mixes medical stone, sulfur, activated carbon, iron powder and polyethylene, and granulates the obtained medical stone-based mixed material to obtain a medical stone matrix.

[0047] In the present invention, the first mixing method is preferably stirring, the stirring speed is preferably 10,000 to 20,000 rpm, more preferably 18,000 rpm, and the stirring time is preferably 0.5 to 1.5 h, more preferably 1.2 to 1.5 h.

[0048] In the present invention, the extrusion granulation is preferably carried out in a screw extruder. In the present invention, the granulation conditions include: the pressure is preferably 0.2-10 MPa, the temperature is preferably 280-430° C., and the holding time is preferably 10 min.

[0049] The present invention performs a second mixing of the microcrystalline cellulose, calcium carbonate, polyhydroxy fatty acid, polyvinyl alcohol, sodium lauryl sulfate and epoxy resin to obtain a coating mixture solution.

[0050] In the present invention, the second mixing is preferably performed by preliminarily mixing microcrystalline cellulose and calcium carbonate, and then mixing the preliminarily mixed material with polyhydroxy fatty acid, polyvinyl alcohol, sodium lauryl sulfate and epoxy resin.

[0051] In the present invention, the initial mixing method is preferably stirring, the stirring speed is preferably 8000-15000 rpm, more preferably 12000 rpm, the time is preferably 40-60 min, more preferably 50 min, and the secondary mixing method is preferably the same as the initial mixing, which will not be repeated.

[0052] After obtaining the coating mixture solution, the coating mixture solution and the medical stone matrix are mixed for the third time under alkaline conditions, and then heated, coated and aged in sequence to obtain the medical stone-based composite filler.

[0053] In the present invention, the alkaline condition is preferably provided by a sodium hydroxide solution, the mass concentration of the sodium hydroxide solution is preferably 20-30%, more preferably 25%. In the present invention, the pH value of the alkaline condition is preferably 10-11.

[0054] In the present invention, the heating is preferably water bath heating, the water bath heating temperature is preferably 70 to 90° C., more preferably 80° C., the heating time is preferably 1 to 2 hours, more preferably 1.5 hours.

[0055] After obtaining the coating mixture solution, the present invention mixes the coating mixture solution and the medical stone matrix for the third time under alkaline conditions, and then performs heating, coating and aging in sequence to obtain the medical stone-based composite filler.

[0056] In the present invention, the heating coating is preferably a water bath heating coating; the temperature of the water bath heating coating is preferably 70 to 90° C., more preferably 80° C., and the time is preferably 1 to 2 hours, more preferably 1.5 hours.

[0057] In the present invention, the aging is preferably heating aging, the temperature of the heating aging is preferably 70 to 90° C., more preferably 80° C., and the time is preferably 1.5 to 2.5 hours, more preferably 2 hours.

[0058] In the present invention, after the aging, the aging product is preferably washed and dried in sequence. In the present invention, the washing agent is preferably deionized water, and the washing is preferably performed until neutral. In the present invention, the drying temperature is preferably 50 to 70°C, more preferably 60°C, and the drying time is preferably 60 minutes.

[0059] The present invention also provides the use of the above-mentioned medical stone-based composite filler in sewage treatment. In the present invention, when used, the shape of the medical stone-based composite filler is preferably cylindrical, and the particle size of the medical stone-based composite filler is preferably 3 to 5 mm, more preferably 4 mm.

[0060] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0061] Example 1

[0062] The parameters of each component in Example 1 are as follows:

[0063] Medical stone: particle size is 200 mesh; porosity is 30%;

[0064] Sulfur: particle size is 200 mesh;

[0065] Activated carbon: particle size is 200 mesh, specific surface area: 1700m 2 / g;

[0066] Iron powder: particle size is 400 mesh;

[0067] High-density polyethylene: weight average molecular weight: 28,000;

[0068] Microcrystalline cellulose: Source: McLean reagent 200 mesh;

[0069] Calcium carbonate: particle size: 150 mesh;

[0070] Polyhydroxy fatty acids: specifically polyhydroxybutyric acid;

[0071] Polyvinyl alcohol: weight average molecular weight: 18000;

[0072] Epoxy resin: Epoxy value: 0.54Eq / 100g.

[0073] In parts by mass, 50 parts of medical stone, 40 parts of sulfur powder, 25 parts of activated carbon, and 15 parts of iron powder are mixed evenly, and then high-density polyethylene is added and stirred at a speed of 18000 rpm for 1.5 hours to obtain a medical stone-based mixture; the medical stone-based mixture is added to a screw granulator for extrusion granulation, and the extrusion granulation conditions are: pressure of 5MPa, temperature control at 300°C, and pressurization time of 10min to obtain a medical stone matrix.

[0074] By weight, 45 parts of microcrystalline cellulose and 15 parts of calcium carbonate are initially mixed, and then mixed with 5 parts of polyhydroxy fatty acid, 10 parts of polyvinyl alcohol, 7 parts of sodium lauryl sulfate and 15 parts of epoxy resin to obtain a coating mixture solution.

[0075] The coating mixture solution and the medical stone matrix are mixed, the pH is adjusted to 11 with a 25wt% NaOH solution, and then placed in a constant temperature water bath at 80°C for heating and coating for 1.5 hours, and aged in an 80°C oven for 2 hours. The resulting product is washed with deionized water until neutral, and then placed in an oven at 60°C for drying to obtain the medical stone-based composite filler.

[0076] Example 2

[0077] The parameters of each component in Example 1 are as follows:

[0078] Medical stone: particle size is 200 mesh; porosity is 30%;

[0079] Sulfur: particle size is 200 mesh;

[0080] Activated carbon: particle size is 200 mesh, specific surface area: 1700m 2 / g;

[0081] Iron powder: particle size is 400 mesh;

[0082] High-density polyethylene: weight average molecular weight: 28,000;

[0083] Microcrystalline cellulose: Source: McLean reagent 200 mesh;

[0084] Calcium carbonate: particle size: 150 mesh;

[0085] Polyhydroxy fatty acids: specifically polyhydroxybutyric acid;

[0086] Polyvinyl alcohol: weight average molecular weight: 18000;

[0087] Epoxy resin: Epoxy value: 0.54Eq / 100g.

[0088] In parts by mass, 35 parts of medical stone, 50 parts of sulfur powder, 25 parts of activated carbon, and 15 parts of iron powder are mixed evenly, and then high-density polyethylene is added and stirred at a speed of 18000 rpm for 1.5 hours to obtain a medical stone-based mixture; the medical stone-based mixture is added to a screw granulator for extrusion granulation under the following conditions: pressure of 5 MPa, temperature control at 300°C, and pressurization time of 10 minutes to obtain a medical stone matrix.

[0089] 30 parts of microcrystalline cellulose and 20 parts of calcium carbonate were initially mixed, and then mixed with 5 parts of polyhydroxy fatty acid, 10 parts of polyvinyl alcohol, 7 parts of sodium lauryl sulfate and 15 parts of epoxy resin to obtain a coating mixture solution.

[0090] The coating mixture solution and the medical stone matrix are mixed, the pH is adjusted to 11 with a 25wt% NaOH solution, and then placed in a constant temperature water bath at 80°C for heating and coating for 1.5 hours, and aged in an 80°C oven for 2 hours. The resulting product is washed with deionized water until neutral, and then placed in an oven at 60°C for drying to obtain the medical stone-based composite filler.

[0091] Example 3

[0092] The parameters of each component in Example 1 are as follows:

[0093] Medical stone: particle size is 200 mesh; porosity is 30%;

[0094] Sulfur: particle size is 200 mesh;

[0095] Activated carbon: particle size is 200 mesh, specific surface area: 1700m 2 / g;

[0096] Iron powder: particle size is 400 mesh;

[0097] High-density polyethylene: weight average molecular weight: 28,000;

[0098] Microcrystalline cellulose: Source: McLean reagent 200 mesh;

[0099] Calcium carbonate: particle size: 150 mesh;

[0100] Polyhydroxy fatty acids: specifically polyhydroxybutyric acid;

[0101] Polyvinyl alcohol: weight average molecular weight: 18000;

[0102] Epoxy resin: Epoxy value: 0.54Eq / 100g.

[0103] In parts by mass, 20 parts of medical stone, 50 parts of sulfur powder, 40 parts of activated carbon, and 15 parts of iron powder are mixed evenly, and then high-density polyethylene is added and stirred at a speed of 18000 rpm for 1.5 hours to obtain a medical stone-based mixture; the medical stone-based mixture is added to a screw granulator for extrusion granulation under the following conditions: pressure of 5 MPa, temperature control at 300°C, and pressurization time of 10 minutes to obtain a medical stone matrix.

[0104] 15 parts of microcrystalline cellulose and 45 parts of calcium carbonate were initially mixed, and then mixed with 5 parts of polyhydroxy fatty acid, 10 parts of polyvinyl alcohol, 7 parts of sodium lauryl sulfate and 15 parts of epoxy resin to obtain a coating mixture solution.

[0105] The coating mixture solution and the medical stone matrix are mixed, the pH is adjusted to 11 with a 25wt% NaOH solution, and then placed in a constant temperature water bath at 80°C for heating and coating for 1.5 hours, and aged in an 80°C oven for 2 hours. The resulting product is washed with deionized water until neutral, and then placed in an oven at 60°C for drying to obtain the medical stone-based composite filler.

[0106] Test Case

[0107] The filler prepared in Example 1 was placed in a 3.5L upflow anaerobic sludge blanket reactor in the laboratory with a filler filling rate of 50% (the volume ratio of the filler to the reactor), and 30% of the autotrophic denitrification sludge of the laboratory mother reactor was inoculated (the autotrophic denitrification sludge was gradually acclimated and cultured by the denitrifying bacteria for 60 days to form a microbial flora dominated by denitrifying thiobacillus with a certain autotrophic denitrification ability). The temperature was controlled at 32°C in a constant temperature water bath. The entire operation process was 60 days and was divided into three stages. The operation process was started by first changing the nitrogen load and gradually shortening the hydraulic retention time. The hydraulic retention time of the first stage was 10 hours and the operation was 20 days. The laboratory simulated influent NH4 + 40mg / L, NO3 - 50mg / L, second stage hydraulic retention time 7h, run 20d laboratory simulated influent NH4 + 70mg / L, NO3 - 80mg / L, third stage hydraulic retention time 4h, operation 20d, laboratory simulated influent NH4 + 40mg / L, NO3 - 50mg / L, sodium acetate was used as the carbon source for the influent, the COD of the influent in the three stages was 70.0mg / L, the C / N ratios of the three stages were 0.78, 0.47, and 0.78 respectively, and it was recorded as the R1 reactor. The results are as follows Figure 1 As shown. Figure 1 Approximately 20 days after biofilm formation, the R1 reactor achieved an ammonia-nitrogen removal rate of 90.22% and a nitrate-nitrogen removal rate of 95.7%. After successful biofilm formation, during the second phase, when the load was increased, the ammonia-nitrogen removal rate reached 94.99% and the nitrate-nitrogen removal rate reached 94.73% after 40 days of operation. During the third phase, when the load was reduced to simulate secondary effluent, the ammonia-nitrogen removal rate reached 97.9% and the nitrate-nitrogen removal rate reached 95.59% after 60 days of operation.

[0108] The filler prepared in Example 2 was placed in a 3.5L upflow anaerobic sludge blanket reactor in the laboratory with a filler filling rate of 50%. 30% of the autotrophic denitrification sludge from the laboratory mother reactor was inoculated and the temperature was controlled at 32°C with a constant temperature water bath. The entire operation process was 60 days and was divided into three stages. The operation process was started by first changing the nitrogen load and gradually shortening the hydraulic retention time. The hydraulic retention time of the first stage was 10 hours and the operation was carried out for 20 days. The laboratory simulated influent NH4 + 40mg / L, NO3 - 50mg / L, second stage hydraulic retention time 7h, run 20d laboratory simulated influent NH4 + 70mg / L, NO3 - 80mg / L, third stage hydraulic retention time 4h, operation 20d, laboratory simulated influent NH4 + 40mg / L, NO3 - 50mg / L, sodium acetate was used as the carbon source for the influent, the COD of the influent in the three stages was 70.0mg / L, the C / N ratios of the three stages were 0.78, 0.47, and 0.78 respectively, and it was recorded as the R2 reactor. The results are as follows Figure 2 As shown. Figure 2 It can be seen that around 20 days after the R2 reactor started forming biofilm, the ammonia nitrogen removal rate reached 84.86% and the nitrate nitrogen removal rate reached 84.12%. After the successful biofilm formation, in the second stage of increasing the load after the successful start-up, the ammonia nitrogen removal rate reached 89.12% and the nitrate nitrogen removal rate reached 90.78% after 40 days of operation. In the third stage of reducing the load to simulate secondary effluent, the ammonia nitrogen removal rate reached 88.66% and the nitrate nitrogen removal rate reached 91.92% after 60 days of operation.

[0109] The filler prepared in Example 3 was placed in a 3.5L upflow anaerobic sludge blanket reactor in the laboratory with a filler filling rate of 50%. 30% of the autotrophic denitrification sludge from the laboratory mother reactor was inoculated and the temperature was controlled at 32°C using a constant temperature water bath. The entire operation process was 60 days and was divided into three stages. The operation process was started by first changing the nitrogen load and gradually shortening the hydraulic retention time. The hydraulic retention time of the first stage was 10 hours and the operation was carried out for 20 days. The laboratory simulated influent NH4 + 40mg / L, NO3 - 50mg / L, second stage hydraulic retention time 7h, run 20d laboratory simulated influent NH4 + 70mg / L, NO3 - 80mg / L, third stage hydraulic retention time 4h, operation 20d, laboratory simulated influent NH4 + 40mg / L, NO3 -50mg / L, sodium acetate was used as the carbon source for the influent, the COD of the influent in the three stages was 70.0mg / L, the C / N ratios of the three stages were 0.78, 0.47, and 0.78 respectively, and it was recorded as the R3 reactor. The results are as follows Figure 3 As shown. Figure 3 Approximately 20 days after biofilm formation, the R3 reactor achieved an ammonia-nitrogen removal rate of 83.17% and a nitrate-nitrogen removal rate of 88.62%. After successful biofilm formation, during the second phase, when the load was increased, the ammonia-nitrogen removal rate reached 86.12% and the nitrate-nitrogen removal rate reached 93.26% after 40 days of operation. During the third phase, when the load was reduced to simulate secondary effluent, the ammonia-nitrogen removal rate reached 87.01% and the nitrate-nitrogen removal rate reached 90.55% after 60 days of operation.

[0110] In summary, after 60 days of operation of the three reactors R1, R2, and R3, the R1 reactor performed well, with rapid biofilm formation and stable effluent. In the later stages, effluent ammonia nitrogen remained below 3 mg / L, with a removal rate exceeding 95%. The R2 reactor, affected by the system pH and the adsorption capacity of the substrate, had a moderate removal rate of around 90%. In the R3 reactor, nitrogen levels initially decreased rapidly, likely due to activated carbon adsorption. However, adsorption reached saturation in the third stage, and R3 struggled to achieve deep denitrification.

[0111] The film-coated modified biological filler based on medical stone not only has a good removal effect on wastewater with high nitrogen load, but also has a deep denitrification effect on urban tail water with low carbon-nitrogen ratio. The application of autotrophic denitrification filler based on medical stone provides a new way to solve the problem of deep denitrification and has practical engineering guidance significance.

[0112] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A medical stone-based composite filler, characterized in that: The invention comprises a medical stone matrix and a coating located in the pores and surface of the medical stone matrix; In parts by mass, the medical stone matrix comprises 50 parts of medical stone; 40 parts of sulfur; 25 parts of activated carbon; 15 parts of iron powder; High-density polyethylene 5-10 parts; In parts by mass, the coating comprises 45 parts of microcrystalline cellulose; 15 parts of calcium carbonate; 5 parts of polyhydroxybutyric acid; and 10 parts of polyvinyl alcohol. 7 parts of sodium lauryl sulfonate and 15 parts of epoxy resin; The particle size of the microcrystalline cellulose is 200 meshes; the particle size of the calcium carbonate powder is 150 meshes.

2. The medical stone-based composite filler according to claim 1, wherein The thickness of the coating is 0.5 to 1 cm.

3. The method for preparing the medical stone-based composite filler according to any one of claims 1 to 2, characterized in that: The following steps are involved: Firstly mixing medical stone, sulfur, activated carbon, iron powder and polyethylene, and granulating the obtained medical stone-based mixture to obtain a medical stone matrix; secondly mixing the microcrystalline cellulose, calcium carbonate, polyhydroxy fatty acid, polyvinyl alcohol, sodium lauryl sulfate and epoxy resin to obtain a coating mixture solution; The coating mixture solution and the medical stone matrix are mixed for the third time under alkaline conditions, and then heated, coated and aged in sequence to obtain the medical stone-based composite filler.

4. The preparation method according to claim 3, characterized in that The heating coating is a water bath heating coating; the temperature of the water bath heating coating is 70 to 90° C., and the time is 1 to 2 hours.

5. The preparation method according to claim 3, characterized in that The aging is heating aging, the temperature of the heating aging is 70-90° C., and the time is 1.5-2.5 hours.

6. Use of the medical stone-based composite filler according to any one of claims 1 to 2 or the medical stone-based composite filler prepared by the preparation method according to any one of claims 3 to 5 in sewage treatment.

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