A biochar filler for denitrification and dephosphorization of rural sewage and a preparation method thereof

Abstract

This invention relates to the field of wastewater treatment technology, specifically to a biochar packing material for nitrogen and phosphorus removal in rural wastewater and its preparation method. The method involves uniformly mixing rice husks (60-80 mesh), straw, polyploid *Arundinaria fangchi* or cow dung with clay at a mass ratio of 1:5 to 1:6, controlling the moisture content of the mixture to approximately 20%, and allowing it to age for 10-15 days. After aging, the mixture is extruded into round strips with a diameter of 15-20 mm and a length of 30-50 mm. After sieving, the strips are calcined in air at 1150-1180℃ for 2 hours to obtain the biochar packing material. The resulting packing material has a porosity of approximately 59%, a compressive strength of approximately 1.2 MPa, and a bulk density of 0.45-0.8 g / cm³. 3 It combines the adsorption properties of biochar with high mechanical strength, is not easily lost and is easy to recycle, can provide attachment sites for microorganisms, and can achieve the synergistic removal of nitrogen and phosphorus in rural sewage through adsorption and biodegradation. It has low raw material cost and no pollution, making it suitable for promotion and application in rural areas.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a biochar packing material for denitrification and phosphorus removal in rural wastewater and its preparation method. Background Technology

[0002] Currently, the direct discharge of rural domestic sewage has become a significant cause of non-point source pollution in rural areas. Domestic sewage generally contains high levels of nitrogen, phosphorus, and organic matter, which can lead to eutrophication of water bodies. Adsorption is a commonly used method for concentrating pollutants from polluted water bodies and has received widespread attention in various wastewater purification research and application fields. Biochar is an adsorbent with widely available raw materials, low cost, and environmental friendliness. Its abundant pores provide ample sites and accessible active sites for pollutant adsorption, effectively removing pollutants such as COD, BOD, ammonia nitrogen, total nitrogen, and total phosphorus from water. Therefore, biochar has broad application prospects in the treatment of rural domestic sewage.

[0003] However, biochar suffers from drawbacks in wastewater treatment, including low strength, short lifespan, and easy loss. Biochar particles have a compressive strength of only 0.15-0.5 MPa, and under hydraulic shear and backwashing, the breakage rate can reach 15%-30% within 3 months, easily leading to fine powder loss, device clogging, rapid increase in head loss, and difficulty in recovery. Furthermore, due to the small particle size of commonly used biochar, its potential as a microbial carrier is not fully utilized in wastewater treatment, making it difficult to achieve synergistic removal of pollutants through adsorption and biodegradation. Therefore, there is an urgent need to develop a biochar packing material and its preparation method for nitrogen and phosphorus removal in rural wastewater to overcome the shortcomings in current practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide a biochar packing material for denitrification and phosphorus removal in rural sewage and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A biochar packing material for denitrification and phosphorus removal in rural sewage is provided. The biochar packing material is made by mixing biomass raw materials with clay and then calcining at high temperature. It has a porous structure and combines the adsorption properties of biochar with the high-strength skeleton formed by clay sintering. It can provide attachment sites for microorganisms and remove nitrogen and phosphorus pollutants in sewage through physical adsorption and microbial metabolism.

[0006] As a further aspect of the present invention: the biomass raw material is selected from one or more of rice husks, straw, polyploid sword-leaf reed, and cow dung.

[0007] As a further aspect of the present invention: the bulk density of the biochar packing is 0.45-0.8 g / cm³.3 The porosity is 59% and the cylinder compressive strength is 1.2 MPa.

[0008] As a further aspect of the present invention: the biochar packing is in the shape of a round bar with a diameter of 15-20 mm and a length of 30-50 mm.

[0009] A method for preparing biochar packing material for denitrification and phosphorus removal in rural sewage as described above includes the following steps: (1) After crushing the biomass raw materials, mix them evenly with clay and adjust the moisture content of the mixture. (2) Place the mixture in a sealed environment to age; (3) Extrude the aged material into round strips and screen out unqualified raw materials; (4) The green body is calcined at high temperature in air atmosphere, and after calcination, it is naturally cooled to room temperature to obtain the biochar filler.

[0010] As a further aspect of the present invention: in step (1), the mass ratio of the biomass raw material to clay is 1:(5-6); The biomass raw materials are pulverized to 60-80 mesh and pretreated to a moisture content of no more than 10%.

[0011] As a further aspect of the present invention: in step (1), the moisture content of the mixture is adjusted to 18%-22%.

[0012] As a further aspect of the present invention: in step (2), the aging temperature is 20-25℃, the relative humidity is 50%-60%, and the aging time is 10-15 days.

[0013] As a further aspect of the present invention: in step (4), the temperature is increased to 1150-1180°C at a rate of 3-5°C / min, and then calcined for 2 hours.

[0014] As a further aspect of the present invention: the clay is kaolin, the particle size of the kaolin is 200 mesh, and the purity is not less than 85%.

[0015] Compared with the prior art, the beneficial effects of the present invention are: The biochar packing material for denitrification and phosphorus removal in rural sewage provided by this invention is made by mixing and firing biomass and clay. The clay is expanded at high temperature to form a porous skeleton with high mechanical strength, so that the fired biochar packing material has both the adsorption performance of biochar and high mechanical strength. At the same time, the formed porous structure provides attachment sites for microorganisms. Biochar filler formed by burning clay and biomass has a large particle size, which can effectively prevent the loss of biochar and facilitate biochar recycling. The biochar packing material has a porosity of approximately 59%, a compressive strength of approximately 1.2 MPa, and a bulk density of 0.45-0.8 g / cm³. 3 It features low cost, no pollution, good nitrogen and phosphorus removal effect, not easy to break and long service life. In rural domestic sewage treatment, it can provide good attachment sites for microorganisms and realize the synergistic removal of pollutants by adsorption and biodegradation. Attached Figure Description

[0016] Figure 1 This is a photograph of the biochar packing material used for nitrogen and phosphorus removal in rural sewage, as described in an embodiment of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0019] Please see Figure 1 This invention provides a biochar packing material for denitrification and phosphorus removal in rural sewage and its preparation method. The method uses agricultural and forestry waste and clay as the main raw materials, and prepares a porous biochar packing material with large particle size and high strength through mixing and aging, extrusion molding and high-temperature calcination. It retains the adsorption performance of biochar, and the skeleton structure formed by high-temperature sintering of clay significantly improves the mechanical strength. At the same time, the rich pore structure provides a large number of attachment sites for microorganisms, which can realize the synergistic removal of nitrogen and phosphorus pollutants in rural domestic sewage by adsorption and biodegradation.

[0020] The general preparation method of the biochar packing material of the present invention is as follows: The biomass raw material, after being dried to a moisture content of ≤10% and impurities such as sand and gravel removed, is pulverized to 60-80 mesh and uniformly mixed with clay (particle size 200 mesh, purity ≥85%) at a mass ratio of 1:5 to 1:6. Deionized water is added, and the moisture content of the mixture is measured and controlled at 20%±2% using a drying method. After stirring evenly, the mixture is aged for 10-15 days in a sealed environment at a temperature of 20-25℃ and a relative humidity of 50%-60%. The aged material is stirred evenly again and extruded into round green bars with a diameter of 15-20mm and a length of 30-50mm using an extruder. After removing the green bars that do not meet the size requirements by sieving through a drum screen, the material is fed into a rotary kiln and heated to 1150-1180℃ at a rate of 3-5℃ / min. It is then calcined in an air atmosphere for 2 hours and allowed to cool naturally to room temperature after calcination to obtain the biochar filler.

[0021] In the above preparation method, controlling the moisture content of the mixture at 20%±2% ensures good plasticity of the material and avoids sticking to the mold or cracking of the green body during extrusion. Sealed aging allows for full hydration of the clay, improving material adhesion and significantly enhancing the mechanical strength of the filler after calcination. A heating rate of 3-5℃ / min prevents rapid escape of biomass volatiles, which could lead to through-cracks in the filler, ensuring structural integrity. A calcination temperature of 1150-1180℃ allows the clay to sinter into a high-strength skeleton while simultaneously enabling full carbonization of the biomass to form a rich porous structure. The prepared biochar filler has a porosity of approximately 59%, a compressive strength of approximately 1.2 MPa, and a bulk density of 0.45-0.8 g / cm³. 3 It has the advantages of high mechanical strength, wear resistance, low leakage, and easy recycling.

[0022] Example 1:

[0023] Rice husks, dried to a moisture content ≤10% and impurities removed, are pulverized to 60-80 mesh and mixed evenly with kaolin (particle size 200 mesh, purity ≥85%) at a mass ratio of 1:5. Deionized water is added, and the moisture content of the mixture is measured and controlled at 20%±2% using a drying method. After thorough mixing, the mixture is aged for 10 days in a sealed environment at 20-25℃ and 50%-60% relative humidity. The aged material is then stirred again and extruded into round green blocks with a diameter of 15-20mm and a length of 30-50mm using an extruder. After removing unqualified green blocks by sieving with a drum screen, the material is fed into a rotary kiln and heated to 1150℃ at a rate of 3-5℃ / min. It is then calcined in air for 2 hours and allowed to cool naturally to room temperature after calcination to obtain rice husk biochar filler.

[0024] Example 2:

[0025] After drying to a moisture content of ≤10% and removing impurities, straw is crushed to 60-80 mesh and mixed evenly with kaolin (particle size 200 mesh, purity ≥85%) at a mass ratio of 1:5.5. Deionized water is added, and the moisture content of the mixture is measured and controlled at 20%±2% using a drying method. After stirring evenly, the mixture is aged for 12 days in a sealed environment at a temperature of 20-25℃ and a relative humidity of 50%-60%. The aged material is stirred evenly again and extruded into round green blocks with a diameter of 15-20mm and a length of 30-50mm using an extruder. After removing unqualified green blocks by sieving with a drum screen, the material is sent to a rotary kiln and heated to 1160℃ at a rate of 3-5℃ / min. It is then calcined in air for 2 hours and allowed to cool naturally to room temperature after calcination to obtain straw biochar filler.

[0026] Example 3:

[0027] The polyploid *Arundinaria fangyinensis*, after being dried to a moisture content ≤10% and impurities removed, is pulverized to 60-80 mesh and uniformly mixed with kaolin (particle size 200 mesh, purity ≥85%) at a mass ratio of 1:6. Deionized water is added, and the moisture content of the mixture is measured and controlled at 20%±2% using a drying method. After stirring evenly, it is aged for 15 days in a sealed environment at a temperature of 20-25℃ and a relative humidity of 50%-60%. The aged material is stirred evenly again and extruded into round green strips with a diameter of 15-20mm and a length of 30-50mm using an extruder. After removing unqualified green strips by sieving with a drum screen, the material is sent to a rotary kiln and heated to 1170℃ at a rate of 3-5℃ / min. It is then calcined in air for 2 hours and allowed to cool naturally to room temperature after calcination to obtain polyploid *Arundinaria fangyinensis* biochar filler.

[0028] Example 4:

[0029] After drying to a moisture content of ≤10% and removing impurities, cow dung is pulverized to 60-80 mesh and mixed evenly with kaolin (particle size 200 mesh, purity ≥85%) at a mass ratio of 1:5.2. Deionized water is added, and the moisture content of the mixture is measured and controlled at 20%±2% using a drying method. After stirring evenly, the mixture is aged for 13 days in a sealed environment at a temperature of 20-25℃ and a relative humidity of 50%-60%. The aged material is stirred evenly again and extruded into round green blocks with a diameter of 15-20mm and a length of 30-50mm using an extruder. After removing unqualified green blocks by sieving with a drum screen, the material is sent to a rotary kiln and heated to 1180℃ at a rate of 3-5℃ / min. The kiln is then calcined in air for 2 hours and allowed to cool naturally to room temperature after calcination to obtain cow dung biochar filler.

[0030] Experimental example: 1. Adsorption performance test of biochar packing material 70g each of the rice husk biochar packing material, straw biochar packing material, polyploid *Arundinaria fanguta* biochar packing material, and cow dung biochar packing material prepared in Examples 1-4 were used to test the adsorption performance of ammonia nitrogen and total phosphorus. The initial pH values ​​of the ammonium chloride and potassium dihydrogen phosphate solutions used in the experiment were adjusted to 7.0±0.2, the shaking amplitude was 20mm, and the reactor was sealed to prevent ammonia nitrogen volatilization.

[0031] 2. Ammonia nitrogen removal rate test Each of the above biochar packing materials was added to 700 mL of a 50 mg / L ammonium chloride solution and cultured on a shaker at 27 °C and 130 r / min for 8 h. After culture, the solution was filtered through a 0.45 μm filter membrane, and the concentration of residual ammonium chloride in the solution was measured by Nessler's reagent spectrophotometry. The ammonia nitrogen removal rate of each biochar packing material was calculated, and the results are shown in Table 1.

[0032] Table 1. Removal rate of ammonia nitrogen by various biochar packing materials 3. Total phosphorus removal rate test Each of the above biochar packing materials was added to 700 mL of a 50 mg / L potassium dihydrogen phosphate solution and cultured on a shaker at 27 °C and 130 r / min for 8 h. After culture, the solution was filtered through a 0.45 μm filter membrane, and the concentration of residual potassium dihydrogen phosphate in the solution was measured using the molybdenum antimony spectrophotometric method. The total phosphorus removal rate of each biochar packing material was calculated, and the results are shown in Table 2.

[0033] Table 2. Total phosphorus removal rate of various biochar packing materials As shown in Tables 1 and 2, the four types of biochar packing materials prepared in this invention all possess certain adsorption capacities for ammonia nitrogen and total phosphorus. Among them, rice bran biochar shows the best removal effect for ammonia nitrogen, while straw biochar shows the best removal effect for total phosphorus. This packing material can initially remove nitrogen and phosphorus pollutants from wastewater through physical adsorption. Simultaneously, its porous structure provides attachment sites for functional microorganisms such as nitrifying bacteria, denitrifying bacteria, and polyphosphate-accumulating bacteria. Through the metabolic activity of these microorganisms, pollutants are further degraded, achieving a synergistic removal process of adsorption and biodegradation, significantly improving the nitrogen and phosphorus removal efficiency of rural domestic wastewater.

[0034] The biochar packing material prepared by this invention can be applied to rural domestic sewage treatment reactors such as biofilters and constructed wetlands. When in use, the packing material is filled into the reactor with a filling rate of 40%-60% and the hydraulic retention time is controlled at 6-12 hours. It can operate stably for a long time, is not easy to break and lose, maintains good performance after backwashing, has a long service life, and the raw materials are widely available and inexpensive, making it suitable for promotion and application in rural areas.

[0035] It should be noted that, in this invention, although the specification describes the embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A biochar packing material for denitrification and phosphorus removal in rural sewage, characterized in that, The biochar packing material is made by mixing biomass raw materials and clay and then calcining at high temperature. It has a porous structure and combines the adsorption properties of biochar with the high-strength skeleton formed by clay sintering. It can provide attachment sites for microorganisms and remove nitrogen and phosphorus pollutants in wastewater through physical adsorption and microbial metabolism.

2. The biochar packing material for denitrification and phosphorus removal in rural sewage according to claim 1, characterized in that, The biomass raw materials are selected from one or more of rice bran, straw, polyploid sword-leaf reed, and cow dung.

3. The biochar packing material for denitrification and phosphorus removal in rural sewage according to claim 1, characterized in that, The bulk density of the biochar packing is 0.45-0.8 g / cm³. 3 The porosity is 59% and the cylinder compressive strength is 1.2 MPa.

4. The biochar packing material for denitrification and phosphorus removal in rural sewage according to claim 1, characterized in that, The biochar packing material is in the shape of round bars, with a diameter of 15-20 mm and a length of 30-50 mm.

5. A method for preparing biochar packing material for denitrification and phosphorus removal in rural sewage as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) After crushing the biomass raw materials, mix them evenly with clay and adjust the moisture content of the mixture. (2) Place the mixture in a sealed environment to age; (3) Extrude the aged material into round strips and screen out unqualified raw materials; (4) The green body is calcined at high temperature in air atmosphere, and after calcination, it is naturally cooled to room temperature to obtain the biochar filler.

6. The method for preparing biochar packing material for denitrification and phosphorus removal in rural sewage according to claim 5, characterized in that, In step (1), the mass ratio of the biomass raw material to clay is 1:(5-6); The biomass raw materials are pulverized to 60-80 mesh and pretreated to a moisture content of no more than 10%.

7. The method for preparing biochar packing material for denitrification and phosphorus removal in rural sewage according to claim 5, characterized in that, In step (1), the moisture content of the mixture is adjusted to 18%-22%.

8. The method for preparing biochar packing material for denitrification and phosphorus removal in rural sewage according to claim 5, characterized in that, In step (2), the aging temperature is 20-25℃, the relative humidity is 50%-60%, and the aging time is 10-15 days.

9. The method for preparing biochar packing material for denitrification and phosphorus removal in rural sewage according to claim 5, characterized in that, In step (4), the temperature is increased to 1150-1180℃ at a rate of 3-5℃ / min and held for calcination for 2 hours.

10. The method for preparing biochar packing material for denitrification and phosphorus removal in rural sewage according to claim 5, characterized in that, The clay is kaolin, and the kaolin has a particle size of 200 mesh and a purity of not less than 85%.

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