A substrate for improving the hydraulic load of a sewage soil filtration system

Abstract

The present invention relates to a method for treating rural sewage by soil infiltration, specifically a substrate for improving the hydraulic load of a rural sewage soil infiltration system. The substrate bed is a mixture of an acidified-hydrothermally modified zeolite mixture and a corn paste-rice husk biochar mixture, which are mixed evenly according to a mass percentage of 15-25%:75-85%. The water content of the mixture reaches 35-40%, and then the substrate is obtained. After the zeolite is acidified-hydrothermally modified in the present invention, its permeability becomes more excellent. It can not only be used as an excellent molecular sieve material, but also be an important component of the substrate to improve the hydraulic characteristics of the substrate bed. Biochar is the product of high-temperature anaerobic pyrolysis of plant residues. It has well-developed pores and regular morphology. It can be used as a soil conditioner to improve soil texture, and at the same time, it can also provide important microstructural support for creating capillary hydraulics processes. The compounding of the above two materials can greatly improve the sewage hydraulic load and perfectly maintain the capillary hydraulics process of the soil infiltration substrate bed.

Description

Technical Field

[0001] The present invention relates to a method for treating rural sewage by soil infiltration, and more specifically to a substrate for improving the hydraulic load of a rural sewage soil infiltration system. Background Art

[0002] As a decentralized sewage land treatment technology, the sewage soil infiltration system is suitable for application in rural communities with relatively small water volumes and strong dispersion. Its principle is to controllably distribute sewage into a soil layer at a certain depth from the surface, with a certain structure and good diffusion performance. Through the capillary infiltration and filtration of the soil, the sewage diffuses around and is purified through processes such as precipitation, filtration, adsorption, biodegradation, and plant root absorption. It is a sewage ecological treatment method that combines natural ecological purification and artificial processes. The soil infiltration system has low investment, low energy consumption, stable effects, and is not affected by seasons, and is suitable for various decentralized sewage deep treatment occasions such as rural areas, suburbs, tourist scenic spots, and resorts.

[0003] The sewage soil infiltration system includes the following types: (1) The Niimi type system, also known as the soil capillary infiltration system. The lower part of the system is an impermeable layer, and the sewage slowly infiltrates upward and around through the capillary action of the soil in the ditch and diffuses into the surrounding soil. The sewage undergoes unsaturated filtration in the matrix layer at a depth of 0.3 - 0.5 m from the surface, and the pollutants are removed under the combined action of aerobic and anaerobic microorganisms. (2) The infiltration ditch system, whose principle is that the sewage is evenly distributed into the infiltration ditches buried in the matrix layer through the water distribution pipes, and then infiltrates, permeates, and diffuses into the surrounding matrix layer. (3) The artificial-natural composite process combines artificial treatment and ecological treatment. The sewage is first pretreated by the artificial treatment process to reduce the pollutant load, and the effluent is further deeply treated by the soil ecological treatment process. No matter which type of sewage soil infiltration system it is, its main process defect can be attributed to the too low hydraulic load. Usually, the suitable hydraulic load of the sewage soil infiltration system is only 0.05 - 0.1 m / m 2 , and in extreme cases, it cannot exceed 0.2 m / m 2 , and the too low hydraulic load results in the need to sacrifice land area to obtain a larger daily sewage treatment volume, thus greatly limiting the popularization and application of this technology.

[0004] To improve the treatment efficiency of sewage soil infiltration systems, the permeability of the matrix bed is generally increased by replacing the original soil with a more permeable matrix material. However, while simply increasing the permeability of the matrix bed can significantly increase the hydraulic load, it also destroys the hydraulic properties of the sewage in the matrix bed. Specifically, when the permeability coefficient is too large, the sewage cannot form capillary flow in the matrix, thus destroying the basic characteristics of the soil infiltration system and compromising the sewage treatment effect. Therefore, the construction or assembly of a matrix bed suitable for high hydraulic loads must simultaneously meet the two conditions of increasing permeability and creating capillary hydraulic processes. Summary of the Invention

[0005] The purpose of the present invention is to address the problem of low treatment efficiency of sewage soil infiltration systems and to provide a substrate for improving the hydraulic load of village and town sewage soil infiltration systems.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A matrix for improving the hydraulic load of a sewage soil infiltration system. The matrix bed is a mixture of an acidified and hydrothermally modified zeolite mixture and a mixture of corn paste and rice husk biochar, which are uniformly mixed in a mass percentage of 15-25%:75-85%. The moisture content of the mixture reaches 35-40%, thereby obtaining the matrix.

[0008] The acidified-hydrothermally modified zeolite mixture is a mixture of acidified-hydrothermally modified zeolite and sand with a particle size of 0.5-1.5 mm; wherein the sand accounts for 40-50% of the mass of the mixture.

[0009] The acidified-hydrothermally modified zeolite is mordenite, which is crushed to 80-100 mesh. The sieve product is immersed in a sulfuric acid solution with a pH of 2.5-5.0 for 40-60 minutes, and then the acid-soaked zeolite is soaked in deionized water for 4-5 hours. After dehydration, it is dried at 100°C for 30-50 minutes. After drying, the dried zeolite is purged with 400-500°C steam for 15-20 minutes to obtain the modified zeolite.

[0010] The corn paste-rice husk biochar mixture is a mixture of corn paste-rice husk biochar and meadow brown soil with a clay silt content of less than 5%, wherein the meadow brown soil with a clay silt content of less than 5% accounts for 60-70% of the mixture by mass.

[0011] The corn paste-rice husk biochar is prepared by crushing corn paste with a moisture content of less than 10% after drying to 0.1-0.5 mm, crushing rice husks with a moisture content of less than 8% after drying to 0.1-0.2 mm, and then mixing the two. The mass percentage of crushed corn paste to crushed rice husks is 20-30%:70-80%. The mixture is placed in a high-temperature anaerobic pyrolysis furnace and heated at a heating rate of 20-30 °C / min to 600-700 °C. After reaching the highest temperature, it is maintained for 4-6 h to obtain the corn paste-rice husk biochar.

[0012] The application of a substrate, the application of the substrate in constructing a sewage soil infiltration system.

[0013] The substrate is filled in the sewage area to be treated, and the laying thickness is 40-50 cm.

[0014] The substrate is filled in the sewage area to be treated. Every 5-10 cm thick is filled, and it is evenly infiltrated with tap water for 1 h. After the laying layer does not drop, continue to lay until the substrate thickness reaches 40-50 cm.

[0015] The present invention has the following advantages:

[0016] The present invention prepares zeolite molecular sieve by acidification-hydrothermal modification of zeolite, and then uses high-temperature adiabatic preparation of biochar from a mixture of corn paste and rice husk materials, and the two are compounded in a certain proportion to prepare a composite substrate with high permeability and mesoporous capillary channels, which is filled in the water-dispersing layer of the substrate bed, thereby improving the treatment efficiency of the sewage soil infiltration system. This method can increase the hydraulic load of the sewage soil infiltration system from 0.1 m / m 2 to 0.6 m / m 2 , and the treatment efficiency is increased by 6 times. In the substrate of the present invention, zeolite molecular sieve is used to improve the permeability of the substrate bed of the soil infiltration system, biochar is used to strengthen the capillary hydraulic trajectory of the substrate bed of the soil infiltration system, and the raw materials used are easily available, the cost is low, the modification measures are simple, and the effect is reliable. Specific embodiments

[0017] The following further describes the present invention in detail through examples.

[0018] After the zeolite of the present invention is acidified-hydrothermally modified, its permeability will become more excellent. It can not only be used as an excellent molecular sieve material, but also as an important component of the substrate to improve the hydraulic characteristics of the substrate bed. Biochar is the product of high-temperature anaerobic pyrolysis of plant residues. It has well-developed pores and regular morphology. It can be used as a soil conditioner to improve soil texture, and it can also provide important microscopic structural support for creating capillary hydraulics processes. Compounding the above two materials can greatly increase the sewage hydraulic load and perfectly maintain the capillary hydraulics process of the soil infiltration substrate bed. Example 1

[0019] 1. Crush the mordenite to 80 mesh. Immerse the sieve undersize fraction in a pH 2.5 sulfuric acid solution for 40 minutes. Drain the solution until bubbles disappear from the zeolite surface. Soak the acid-soaked zeolite in deionized water for 4 hours. Dehydrate and dry at 100°C for 30 minutes. Purge the dried zeolite with 400°C steam for 15 minutes. Air-dry and mix uniformly with 0.5 mm sand, denoted as Matrix FS. Sand constitutes 40% of the Matrix FS by mass and is set aside.

[0020] 2. Crush dried corn paste with a moisture content of less than 10% to 0.1 mm, and crush dried rice husks with a moisture content of less than 8% to 0.1 mm, then mix the two, with the crushed corn paste and crushed rice husk ratio being 20%:80% by mass. Place the mixed corn paste and rice husk powder in a high-temperature, oxygen-free pyrolysis furnace, heat the temperature to 600°C at a rate of 20°C / min, and maintain the temperature for 4 hours to produce corn paste-rice husk biochar. The corn paste-rice husk biochar is then mixed evenly with meadow brown soil with a clay content of less than 5%, referred to as the substrate BS, where the meadow brown soil accounts for 60% of the BS by mass and is set aside.

[0021] 3. The matrix FS and the matrix BS were mixed evenly in a mass percentage of 15%:85%, sprayed with tap water, and the moisture content of the mixture was adjusted to 35% to obtain the final matrix.

[0022] 4. The final matrix is laid in the diffused water layer of the sewage soil infiltration system with a laying thickness of 40 cm. During the laying process, every 5-10 cm thick is filled and evenly infiltrated with tap water for 1 hour. After the laying layer does not drop, continue to lay the final matrix until it reaches 40 cm.

[0023] 5. Taking the pollutant discharge standard of urban sewage treatment plants (GB 18918-2002) Level A as the treatment effect standard, compared with the traditional sewage soil infiltration system, the hydraulic load of the sewage soil infiltration system of the present invention can be reduced from 0.1m / m 2 Increased to 0.59m / m 2 . Example 2

[0024] 1. Crush the mordenite to 90 mesh. Immerse the sieve undersize fraction in a pH 4.0 sulfuric acid solution for 50 minutes. Drain the solution until bubbles disappear from the zeolite surface. Soak the acid-soaked zeolite in deionized water for 4.5 hours. Dehydrate and dry at 100°C for 40 minutes. Purge the dried zeolite with 450°C steam for 18 minutes. Air-dry and mix with 1.0 mm sand, referred to as matrix FS. The sand constitutes 45% of the matrix FS by mass and set aside.

[0025] 2. Crush corn paste having a moisture content of less than 10% after drying to 0.3 mm, and crush rice husks having a moisture content of less than 8% after drying to 0.15 mm, and then mix the two, with the crushed corn paste and crushed rice husks mixed in a ratio of 25% by mass to 75% by mass. Place the mixed corn paste and rice husk powder in a high-temperature anaerobic pyrolysis furnace, heat the temperature to 650°C at a rate of 25°C / min, and maintain the temperature for 5 hours to produce corn paste-rice husk biochar. Then, mix the corn paste-rice husk biochar with meadow brown soil having a clay content of less than 5%, and record it as the substrate BS, wherein the meadow brown soil accounts for 65% of the BS by mass, and set aside.

[0026] 3. The matrix FS and the matrix BS were mixed evenly in a mass percentage of 20%:80%, sprayed with tap water, and the moisture content of the mixture was adjusted to 37% to obtain the final matrix.

[0027] 4. The final matrix is laid in the diffused water layer of the sewage soil infiltration system with a laying thickness of 45 cm. During the laying process, every 5-10 cm thick is filled and evenly infiltrated with tap water for 1 hour. After the laying layer does not drop, continue to lay the final matrix until it reaches 45 cm.

[0028] 5. Taking the Class A of Pollutant Discharge Standard for Urban Wastewater Treatment Plants (GB 18918-2002) as the treatment effect standard, compared with the soil infiltration system of conventional sewage, the hydraulic load of the sewage soil infiltration system of the present invention can be reduced from 0.1m / m 2 Increased to 0.54m / m 2 . Example 3

[0029] 1. Crush the mordenite to 100 mesh. Immerse the sieve undersize fraction in a pH 5.0 sulfuric acid solution for 60 minutes. Drain the solution until bubbles disappear from the zeolite surface. Soak the acid-soaked zeolite in deionized water for 5 hours. Dehydrate and dry at 100°C for 50 minutes. Purge the dried zeolite with 500°C steam for 20 minutes. Air-dry and mix uniformly with 1.5 mm sand, denoted as Matrix FS. Sand constitutes 50% of the Matrix FS by mass and set aside.

[0030] 2. Crush the corn paste with a moisture content of less than 10% after drying to 0.5 mm, and crush the rice husks with a moisture content of less than 8% after drying to 0.2 mm. Then mix the two, and mix them evenly at a mass percentage of 30%:70% of the crushed corn paste to the crushed rice husks. Place the mixed corn paste and rice husk powder in a high-temperature anaerobic pyrolysis furnace, heat it up to 700 °C at a heating rate of 30 °C / min, and maintain it for 6 h after reaching the temperature to prepare corn paste-rice husk biochar; then mix the corn paste-rice husk biochar evenly with meadow brown soil with a clay particle content of less than 5%, denoted as matrix BS, where meadow brown soil accounts for 75% of the mass of BS, and set aside.

[0031] 3. Mix the matrix FS and matrix BS evenly at a mass percentage of 25%:75%, spray with tap water, and adjust the moisture content of the mixed material to 40% to compound the final matrix.

[0032] 4. Lay the final matrix on the water-dispersing layer of the sewage soil infiltration system, with a laying thickness of 50 cm. During the laying process, every 5 - 10 cm thick is filled, and tap water is evenly infiltrated for 1 h. After the laying layer does not drop, continue to lay the final matrix until 50 cm.

[0033] 5. Taking the pollutant discharge standard of urban sewage treatment plants (GB 18918 - 2002) Class A as the treatment effect standard, compared with the soil infiltration system for conventional sewage, the hydraulic load of the sewage soil infiltration system of the present invention can be increased from 0.1 m / m 2 to 0.58 m / m 2 . Example 4

[0034] 1. Crush the mordenite to 100 mesh, take the undersize product and mix it evenly with sand with a particle size of 1.5 mm, denoted as NFS, where sand accounts for 50% of the mass of matrix NFS, and set aside.

[0035] 2. Crush the corn paste with a moisture content of less than 10% after drying to 0.5 mm, and crush the rice husks with a moisture content of less than 8% after drying to 0.2 mm. Then mix the two, and mix them evenly at a mass percentage of 30%:70% of the crushed corn paste to the crushed rice husks. Place the mixed corn paste and rice husk powder in a high-temperature anaerobic pyrolysis furnace, heat it up to 700 °C at a heating rate of 30 °C / min, and maintain it for 6 h after reaching the temperature to prepare corn paste-rice husk biochar; then mix the corn paste-rice husk biochar evenly with meadow brown soil with a clay particle content of less than 5%, denoted as matrix BS, where meadow brown soil accounts for 75% of the mass of BS, and set aside.

[0036] 3. Mix the matrix NFS and the matrix BS evenly at a mass percentage of 25%:75%, spray with tap water, adjust the moisture content of the mixed material to 40%, and compound to obtain the final matrix.

[0037] 4. Lay the final matrix on the water-dispersing layer of the sewage soil infiltration system, with a laying thickness of 50 cm. During the laying process, for every 5-10 cm thickness filled, uniformly infiltrate with tap water for 1 h. After the laying layer does not drop, continue to lay the final matrix until it reaches 50 cm.

[0038] 5. Taking the first-class A of the pollutant discharge standard for urban sewage treatment plants (GB 18918-2002) as the treatment effect standard, compared with the conventional sewage soil infiltration system, the hydraulic load of the sewage soil infiltration system of the present invention can be increased from 0.1 m / m 2 to 0.25 m / m 2 , with a slight increase in the hydraulic load, but far lower than the improvement effect of the acidification-hydrothermal modified zeolite and the corn paste-rice husk biochar mixture on the hydraulic load.

Claims

1. A substrate for improving the hydraulic load of a sewage soil filtration system, characterized in that: The mixture of acidified-hydrothermally modified zeolite mixture and corn paste-rice husk biochar is mixed evenly according to the mass percentage of 15-25% : 75-85%, and the water content of the mixture reaches 35-40%, thus obtaining the substrate; The acidified-hydrothermally modified zeolite mixture is a mixture of acidified-hydrothermally modified zeolite and sand with a particle size of 0.5-1.5 mm; among them, the sand accounts for 40-50% of the mass of the mixture; The acidified-hydrothermally modified zeolite is mordenite, which is crushed to 80-100 meshes, and the undersize is immersed in a sulfuric acid solution with pH = 2.5-5.0 for 40-60 min, and then the acid-leached zeolite is soaked in deionized water for 4-5 h, dehydrated and dried at 100 °C for 30-50 min. After drying, the dried zeolite is purged with steam at 400-500 °C for 15-20 min, thus obtaining the modified zeolite; The mixture of corn paste-rice husk biochar is a mixture of corn paste-rice husk biochar and meadow brown soil with a clay silt content of less than 5%; among them, the meadow brown soil with a clay silt content of less than 5% accounts for 60-70% of the mass of the mixture; The corn paste-rice husk biochar is obtained by crushing corn paste with a water content of less than 10% after drying to 0.1-0.5 mm, crushing rice husk with a water content of less than 8% after drying to 0.1-0.2 mm, and then mixing the two. The mass percentage of crushed corn paste to crushed rice husk is 20-30% : 70-80%; after mixing, it is placed in a high-temperature anaerobic pyrolysis furnace and heated to 600-700 °C at a heating rate of 20-30 °C / min. After reaching the highest temperature, it is maintained for 4-6 h to prepare the corn paste-rice husk biochar.

2. Use of the substrate according to claim 1, characterized in that: The application of the substrate in constructing a sewage soil infiltration system.

3. The application according to claim 2, characterized in that: The substrate is filled in the sewage area to be treated, and the laying thickness is 40-50 cm.

4. The application according to claim 3, characterized in that: The substrate is filled in the sewage area to be treated. Every 5-10 cm thick is filled, and it is evenly infiltrated with tap water for 1 h. After the laying layer does not drop, continue to lay until the substrate thickness reaches 40-50 cm.