A method for preventing groundwater leakage in waste treatment plants

Abstract

The application belongs to the technical field of landfill anti-seepage, and specifically discloses a groundwater anti-seepage treatment method for a waste treatment plant. The method comprises the following steps: laying an exhaust layer on the upper side of a waste pile, wherein the exhaust layer is composed of gravel; laying an under-membrane protection layer on the upper side of the exhaust layer, wherein the under-membrane protection layer is composed of modified clay; laying an HDPE geomembrane on the upper side of the under-membrane protection layer, and laying an over-membrane protection layer on the upper side of the HDPE geomembrane; laying a drainage layer on the upper side of the over-membrane protection layer; and laying a green soil layer on the upper side of the drainage layer, and the treatment method is obtained. Raw material components of the modified clay include modified attapulgite, sodium carboxymethyl cellulose, modified zeolite, betaine, polyvinyl alcohol, deionized water, defoaming agent and water reducing agent. The drainage net comprises a modified polyethylene fiber layer, a polyethylene interlayer and a geotextile layer. The treatment method has good effects and excellent anti-seepage and anti-leakage effects.

Description

Technical Field

[0001] This application relates to the technical field of landfill seepage prevention, and in particular to a method for preventing groundwater leakage in waste treatment plants. Background Technology

[0002] With the rapid development of my country's economy and the acceleration of the process of building civilized cities, people's requirements for the urban environment are getting higher and higher, and the amount of urban domestic waste is also increasing, which has brought adverse effects to the environment. At present, the main methods of domestic waste disposal are composting, landfilling and incineration. Among them, composting and incineration have certain drawbacks, while landfilling is the most widely used disposal method.

[0003] Landfilling refers to the process of placing urban waste in low-lying areas and then covering the pile with soil to create land. During landfilling, some waste is not treated to render it harmless, leaving behind a large number of bacteria, viruses, and heavy metal pollutants. These pollutants are easily discharged with leachate, polluting nearby land and groundwater, thus wasting natural resources. Summary of the Invention

[0004] In order to improve the problem of pollutants in waste being discharged with leachate, thereby polluting nearby land and groundwater, this application provides a method for preventing groundwater leakage in waste treatment plants.

[0005] This application provides a method for preventing groundwater leakage in waste treatment plants, which adopts the following technical solution:

[0006] A method for preventing groundwater seepage in a waste treatment plant includes the following steps:

[0007] (1) Lay an exhaust layer on the upper side of the garbage pile. The exhaust layer is composed of crushed stone with a particle size of 25-50mm and a thickness of 30-40cm.

[0008] (2) A protective layer under the membrane is laid on the upper side of the venting layer. The protective layer under the membrane is composed of modified clay.

[0009] (3) Lay an HDPE geomembrane on the upper side of the lower protective layer. The thickness of the HDPE geomembrane is 1.5-2mm. Lay an upper protective layer on the upper side of the HDPE geomembrane. The upper protective layer is a three-dimensional composite drainage net.

[0010] (4) A drainage layer is laid on the upper side of the protective layer on the membrane. The drainage layer is composed of gravel with a particle size of 20-30mm and a thickness of 20-30cm.

[0011] (5) A green soil layer is laid on the upper side of the drainage layer, and the thickness of the green soil layer is 16-20cm.

[0012] The raw material components of the modified clay include: modified attapulgite, sodium carboxymethyl cellulose, modified zeolite, betaine, polyvinyl alcohol, deionized water, defoamer, and water-reducing agent.

[0013] The drainage net comprises a modified polyethylene fiber layer, a polyethylene interlayer, and a geotextile layer.

[0014] By adopting the above technical solution, the venting layer is composed of crushed stone and serves as the bottom layer of the sealed waste pile, supporting the entire waste pile and venting the waste gas generated by waste decomposition. The protective layer under the membrane is composed of modified clay, which can bond the venting layer and ensure its structural stability. Moreover, the modified clay can also bond the HDPE geomembrane, ensuring its structural stability. The HDPE geomembrane has the functions of seepage prevention, waterproofing, and isolation. It not only effectively blocks the growth of flies and bacteria and the spread of waste odors, but also blocks the infiltration of external rainwater, dew, and other moisture, preventing groundwater pollution.

[0015] The membrane protective layer is set as a three-dimensional composite drainage net, and a drainage layer is laid on the upper side of the membrane protective layer. The function of the drainage net and the drainage layer is to drain the rainwater that seeps in from the upper part in time and play a buffering role. Rainwater and surface water seep into the drainage layer through the green soil layer above, and then the drainage layer drains the seepage water from the upper layer, thereby preventing a large amount of rainwater from seeping in and damaging the impermeable layer, generating a large amount of leachate, and protecting the stability of the lower impermeable layer.

[0016] The greening soil layer is mainly planted with vegetation or turf. If the root system of the greening soil layer extends into the HDPE geomembrane, the HDPE geomembrane ensures resistance to plant roots. HDPE geomembrane has excellent puncture resistance and can resist most plant roots.

[0017] Among the raw material components of modified clay, modified attapulgite has good adsorption properties, capable of adsorbing toxic gases released from waste, reducing the seepage of toxic gases from the protective layer under the membrane into the air and thus polluting the environment. Simultaneously, the HDPE geomembrane further prevents seepage, further inhibiting the seepage of toxic gases. Sodium carboxymethyl cellulose dissolves in deionized water to produce viscosity, which can bind modified attapulgite and modified zeolite, resulting in a tight structural connection in the modified clay. Modified zeolite has a large surface area and pore volume, exhibiting strong adsorption capacity, and can be loaded onto the modified attapulgite. The surface and pores further enhance the adsorption capacity and bonding tightness of the modified attapulgite; betaine has a bactericidal effect, which can reduce bacteria and fungi in the landfill, and can also adjust the viscosity of the modified clay system, so that the components are mixed evenly; polyvinyl alcohol has lubricating, solubilizing and film-forming properties, which can adjust the mixing uniformity of the components, and can also coat the modified attapulgite, so that the modified zeolite and modified attapulgite are tightly connected, and further increase the connectivity between other components, and further increase the seepage prevention and leakage prevention performance of the modified clay.

[0018] The drainage net consists of a modified polyethylene fiber layer, a polyethylene interlayer, and a geotextile layer. The modified polyethylene fiber layer features high strength, wear resistance, and excellent impact resistance. The polyethylene interlayer provides mechanical protection and corrosion prevention. The geotextile layer provides reinforcement, filtration, drainage, protection, and puncture resistance. The combination of the modified polyethylene fiber layer, polyethylene interlayer, and geotextile layer has good water conductivity, allowing the main body to form drainage channels to discharge excess gas and water, further reducing the probability of water entering the HDPE geomembrane, thereby improving the efficiency of landfill.

[0019] Preferably, the modified clay comprises, by weight, the following raw material components: 50-60 parts modified attapulgite, 10-15 parts sodium carboxymethyl cellulose, 15-30 parts modified zeolite, 5-10 parts betaine, 20-30 parts polyvinyl alcohol, 75-85 parts deionized water, 1-5 parts defoamer, and 2-6 parts water-reducing agent.

[0020] By adopting the above technical solution and further limiting the mass ratio of each component, a modified clay with better seepage prevention and adsorption effects is obtained. Modified attapulgite and modified zeolite have good adsorption properties and can adsorb toxic gases. Sodium carboxymethyl cellulose and polyvinyl alcohol further increase the adhesion between modified attapulgite and modified zeolite. At the same time, the film coating of modified attapulgite and modified zeolite further increases the seepage prevention and leakage prevention performance of the modified clay system. Betaine adjusts the viscosity of the system, thereby increasing the mixing uniformity between the components. Through the synergistic effect of the above components, the seepage prevention and leakage prevention effect of the modified clay system is improved, which helps to further inhibit the emission of toxic gases and inhibit the entry of moisture into the landfill.

[0021] Preferably, the method for preparing the modified attapulgite includes the following steps:

[0022] (1) Crush and grind the attapulgite, then disperse it in oxalic acid solution, stir at 60-70℃ for 2-3 hours, filter, and calcine at 350-380℃ for 1-2 hours to obtain pretreated attapulgite.

[0023] (2) Disperse straw fibers in anhydrous ethanol, then add nano titanium dioxide, sonicate for 1-3 hours, filter, and dry to obtain modified straw fibers.

[0024] (3) Disperse the pretreated attapulgite in step (1) in deionized water, then add the modified straw fiber from step (2), stir at 80-90℃ for 2-3 hours, then add xanthan gum and continue stirring to obtain modified attapulgite.

[0025] By adopting the above technical solution, oxalic acid is used to treat the surface of attapulgite, which erodes the surface of attapulgite to a certain extent, making the surface of attapulgite rough. Then, it is further calcined to increase the specific surface area of ​​attapulgite.

[0026] The surface of straw fibers has a large number of grooves. Nano-titanium dioxide is loaded in the grooves of straw fibers, which increases the mechanical properties of straw fibers. Moreover, nano-titanium dioxide has the functions of sterilization, anti-fouling and deodorization, which can reduce the number of bacteria and fungi generated in the garbage pile and further purify the environment.

[0027] The modified straw fibers were mixed with pretreated attapulgite, and the straw fibers were loaded on the surface of the attapulgite, further increasing the specific surface area of ​​the attapulgite and thus improving its adsorption capacity. In addition, xanthan gum bonded the straw fibers and attapulgite together, increasing the connectivity between them and thus improving the mechanical properties of the attapulgite. This helps to improve the mechanical properties, adhesion and adsorption properties of the modified clay in the future.

[0028] Preferably, the mass ratio of the attapulgite clay, straw fiber, and nano-titanium dioxide is 1:0.1-0.3:0.05-0.08.

[0029] By adopting the above technical solution, the mass ratio of attapulgite, straw fiber, and nano-titanium dioxide is further limited within a certain range, resulting in modified clay with superior mechanical properties, adhesion, and adsorption properties. Nano-titanium dioxide is loaded on the surface of straw fiber, and straw fiber is loaded on the surface of attapulgite, further improving the adhesion, mechanical properties, and adsorption properties of attapulgite, which is helpful for subsequent seepage prevention and leakage prevention treatment.

[0030] Preferably, the modified zeolite is pretreated by the following method: dispersing natural zeolite in wood vinegar, stirring for 1-3 hours, filtering, then adding it to a hexadecyltrimethylammonium bromide solution, adding serpentine powder, stirring evenly, filtering, and drying to obtain the modified zeolite.

[0031] By adopting the above technical solution, wood vinegar exhibits strong antioxidant, anti-inflammatory, antiviral, and antibacterial activities. The wood vinegar erodes the surface of natural zeolite to a certain extent, increasing its specific surface area. Then, hexadecyltrimethylammonium bromide solution activates the surface of natural zeolite, further expanding its porosity. Serpentine powder, with its heat resistance, corrosion resistance, and wear resistance, can be loaded onto the surface of natural zeolite, increasing its mechanical properties, bactericidal properties, and adsorption properties. This, in turn, facilitates the loading of modified zeolite with other components, further modifying the clay.

[0032] Preferably, the defoamer is selected from one or more of fatty alcohol polyoxyethylene ether, liquid paraffin, and polyether.

[0033] By adopting the above technical solution, the defoamer is used to reduce the probability of generating bubbles during the component mixing process, improve the uniformity of mixing of each component, and help to make the components in the modified clay mix evenly, so as to obtain a modified clay with a dense structure.

[0034] Preferably, the water-reducing agent is a polycarboxylate-based water-reducing agent and / or a naphthalene-based water-reducing agent.

[0035] By adopting the above technical solution, the water-reducing agent is used to change the viscosity and fluidity of the system, thereby enhancing the strength, durability and weather resistance of the modified clay.

[0036] Preferably, the method for preparing the modified polyethylene fiber layer includes the following steps:

[0037] (1) Mix polyethylene, bamboo nanofiber, cotton fiber, ethylene glycol and basalt fiber, stir at 90-95℃ for 3-5 hours, then add compatibilizer and antioxidant, stir evenly, melt and knead, extrude, cool, granulate and dry to obtain polyethylene layer material.

[0038] (2) Disperse carbon nanotubes in deionized water, then add acetic acid solution, stir for 1-2 hours, then add chitosan and polyethylene layer material obtained in step (1), and then perform hot pressing to obtain modified polyethylene fiber layer.

[0039] By adopting the above technical solutions, polyethylene has excellent heat resistance, corrosion resistance, impact resistance and fatigue resistance, bamboo nanofiber has the functions of moisture absorption and breathability, antibacterial and bacteriostatic properties, UV resistance and deodorization and adsorption, cotton fiber has good water absorption, basalt fiber has good mechanical properties, and the polyethylene layer material obtained by mixing the above raw materials has good mechanical properties and antibacterial properties.

[0040] Carbon nanotubes have a very high surface area ratio and good mechanical properties. Chitosan is used to coat carbon nanotubes and polyethylene layer material obtained in step (1). Carbon nanotubes are loaded on the surface of polyethylene layer material. Chitosan coats carbon nanotubes and polyethylene layer material, which further increases the adhesion of carbon nanotubes on the surface of polyethylene layer material, thereby improving the mechanical properties of the system.

[0041] Preferably, the mass ratio of polyethylene, carbon nanotubes and chitosan is 1:0.3-0.6:0.02-0.05.

[0042] By adopting the above technical solution, the mass ratio of polyethylene, carbon nanotubes and chitosan is further limited within a certain range, resulting in a modified polyethylene fiber layer with good mechanical properties. Polyethylene has excellent heat resistance, corrosion resistance, impact resistance and fatigue resistance, while carbon nanofibers have excellent mechanical properties. Carbon nanofibers are loaded on the surface of polyethylene, and chitosan coats the polyethylene, further increasing the connectivity between carbon nanotubes and polyethylene, thereby improving the mechanical properties and other corresponding properties of polyethylene.

[0043] Preferably, the method for preparing the drainage net includes the following steps: coating one side of the modified polyethylene fiber layer with epoxy resin adhesive, and then bonding it to one side of the polyethylene interlayer; coating the side of the polyethylene interlayer away from the modified polyethylene fiber layer with epoxy resin adhesive, and then bonding the geotextile layer to obtain the drainage net.

[0044] By adopting the above technical solution and using epoxy resin adhesive for bonding, the resulting drainage net has good mechanical properties and structural stability, and can be used for a long time.

[0045] In summary, this application has the following beneficial effects:

[0046] 1. In this application, the venting layer is composed of crushed stone and serves as the bottom layer of the enclosed waste pile, supporting the entire waste pile and venting the exhaust gas generated by waste decomposition. The protective layer under the membrane is composed of modified clay, which can bond the venting layer and ensure its structural stability. Moreover, the modified clay can also bond the HDPE geomembrane, ensuring its structural stability. The HDPE geomembrane has the functions of seepage prevention, waterproofing, and isolation. It not only effectively blocks the growth of flies and bacteria and the spread of waste odors, but also blocks the infiltration of external rainwater, dew, and other moisture, preventing groundwater pollution.

[0047] 2. In the raw material components of the modified clay in this application, the modified attapulgite has good adsorption properties, which can adsorb toxic gases released from garbage, reduce the leakage of toxic gases from the protective layer under the membrane into the air and thus pollute the environment. At the same time, the HDPE geomembrane further prevents seepage and further inhibits the leakage of toxic gases. Sodium carboxymethyl cellulose dissolves in deionized water to produce viscosity, which can bind the modified attapulgite and modified zeolite, making the modified clay structure tightly connected.

[0048] 3. The modified zeolite in this application has a large surface area and pore volume, and a strong adsorption capacity. The modified zeolite can be loaded on the surface and in the pores of the modified attapulgite, further increasing the adsorption capacity and tightness of the modified attapulgite. Betaine has a bactericidal effect, which can reduce bacteria and fungi in the landfill, and can also adjust the viscosity of the modified clay system, so that the components are mixed evenly. Polyvinyl alcohol has lubricating, solubilizing and film-forming properties, which can adjust the uniformity of the components and can also coat the modified attapulgite, so that the modified zeolite and modified attapulgite are tightly connected, and further increase the connectivity between other components, further increasing the seepage prevention and leakage prevention performance of the modified clay. Detailed Implementation

[0049] The present application will be further described in detail below with reference to the embodiments.

[0050] The raw materials used in the examples and comparative examples are all commercially available. The defoamer is fatty alcohol polyoxyethylene ether, and the water-reducing agent is a polycarboxylate water-reducing agent.

[0051] Preparation example of modified attapulgite

[0052] Preparation Example 1-1

[0053] The preparation method of modified attapulgite includes the following steps:

[0054] (1) 1.5 kg of attapulgite was crushed and ground, then dispersed in 3 L of oxalic acid solution with a mass fraction of 10%, stirred at 65°C for 3 h, filtered, and calcined at 360°C for 2 h to obtain pretreated attapulgite.

[0055] (2) Disperse straw fibers in 2L of anhydrous ethanol, then add nano titanium dioxide, sonicate for 3h, filter, and dry to obtain modified straw fibers.

[0056] (3) Disperse the pretreated attapulgite in step (1) in 3L of deionized water, then add the modified straw fiber in step (2), stir at 85℃ for 3h, then add 0.2kg xanthan gum and continue stirring to obtain modified attapulgite; wherein, the mass ratio of attapulgite, straw fiber and nano titanium dioxide is 1:0.1:0.08.

[0057] Preparation Examples 1-2

[0058] The difference from preparation example 1-1 is that step (1) is not performed.

[0059] Preparation Examples 1-3

[0060] The difference from Preparation Example 1-1 is that no straw fiber is added.

[0061] Preparation Examples 1-4

[0062] The difference from Preparation Example 1-1 is that no nano-titanium dioxide is added.

[0063] Preparation Examples 1-5

[0064] The difference from Preparation Example 1-1 is that the mass ratio of attapulgite clay, straw fiber and nano titanium dioxide is 1:0.3:0.05.

[0065] Preparation Examples 1-6

[0066] The difference from Preparation Example 1-1 is that the mass ratio of attapulgite clay, straw fiber and nano titanium dioxide is 1:0.7:0.01.

[0067] Preparation example of modified polyethylene fiber layer

[0068] Preparation Example 2-1

[0069] The method for preparing the modified polyethylene fiber layer includes the following steps:

[0070] (1) Mix 1 kg polyethylene, 0.2 kg bamboo nanofiber, 0.1 kg cotton fiber, 2 kg ethylene glycol and 0.5 kg basalt fiber, stir at 95℃ for 4 h, then add 0.2 kg PVC compatibilizer and 0.1 kg antioxidant 1010, stir evenly, melt mix and extrude, then cool, granulate and dry to obtain polyethylene layer material;

[0071] (2) Disperse carbon nanotubes in 2L of deionized water, then add 0.9kg of acetic acid solution with a mass concentration of 10%, stir for 2h, then add chitosan and polyethylene layer material obtained in step (1), and then perform hot pressing to obtain modified polyethylene fiber layer; wherein, the mass ratio of polyethylene, carbon nanotubes and chitosan is 1:0.3:0.05.

[0072] Preparation Example 2-2

[0073] The difference from preparation example 2-1 is that carbon nanotubes are not added.

[0074] Preparation Examples 2-3

[0075] The difference from Preparation Example 2-1 is that chitosan is not added.

[0076] Preparation Examples 2-4

[0077] The difference from Preparation Example 2-1 is that the mass ratio of polyethylene, carbon nanotubes and chitosan is 1:0.6:0.02.

[0078] Preparation Examples 2-5

[0079] The difference from Preparation Example 2-1 is that the mass ratio of polyethylene, carbon nanotubes and chitosan is 1:0.9:0.01.

[0080] Example

[0081] Example 1

[0082] A method for preventing groundwater seepage in a waste treatment plant includes the following steps:

[0083] (1) Lay an exhaust layer on the upper side of the garbage heap. The exhaust layer is composed of crushed stone with a particle size of 25-50mm and a thickness of 35cm.

[0084] (2) A protective layer under the membrane is laid on the upper side of the venting layer. The protective layer under the membrane is composed of modified clay.

[0085] (3) Lay an HDPE geomembrane on the upper side of the lower protective layer. The thickness of the HDPE geomembrane is 2mm. Lay an upper protective layer on the upper side of the HDPE geomembrane. The upper protective layer is a three-dimensional composite drainage net.

[0086] (4) A drainage layer is laid on the upper side of the protective layer of the membrane. The drainage layer is composed of gravel with a particle size of 20-30mm and a thickness of 25cm.

[0087] (5) A green soil layer is laid on the upper side of the drainage layer, and the thickness of the green soil layer is 20cm.

[0088] The drainage net consists of a modified polyethylene fiber layer, a polyethylene interlayer, and a geotextile layer.

[0089] The modified clay, by weight, comprises the following raw material components: 60 kg of modified attapulgite, 10 kg of sodium carboxymethyl cellulose, 30 kg of modified zeolite, 10 kg of betaine, 30 kg of polyvinyl alcohol, 85 kg of deionized water, 5 kg of defoamer, and 6 kg of water-reducing agent.

[0090] The modified zeolite was pretreated by the following method: natural zeolite was dispersed in 5L of wood vinegar, stirred for 3 hours, filtered, and then added to 0.2kg of cetyltrimethylammonium bromide solution, followed by 0.6kg of serpentine powder. The mixture was stirred evenly, filtered, and dried to obtain the modified zeolite.

[0091] The method for preparing a drainage net includes the following steps: coating one side of a modified polyethylene fiber layer with an epoxy resin adhesive, and then bonding it to one side of a polyethylene interlayer; coating the side of the polyethylene interlayer away from the modified polyethylene fiber layer with an epoxy resin adhesive, and then bonding a geotextile layer to obtain a drainage net.

[0092] The modified attapulgite was prepared using Preparation Example 1-1, and the modified polyethylene fiber layer was prepared using Preparation Example 2-1.

[0093] Example 2

[0094] A method for preventing groundwater leakage in a waste treatment plant, which differs from Example 1, is that the modified clay, by weight, includes the following raw material components: 50 kg of modified attapulgite, 15 kg of sodium carboxymethyl cellulose, 15 kg of modified zeolite, 5 kg of betaine, 20 kg of polyvinyl alcohol, 75 kg of deionized water, 1 kg of defoamer, and 2 kg of water-reducing agent.

[0095] Example 3

[0096] A method for preventing groundwater leakage in a waste treatment plant, which differs from Example 1, is that the modified clay, by weight, includes the following raw material components: 80 kg of modified attapulgite, 5 kg of sodium carboxymethyl cellulose, 10 kg of modified zeolite, 15 kg of betaine, 35 kg of polyvinyl alcohol, 100 kg of deionized water, 0.5 kg of defoamer, and 1 kg of water-reducing agent.

[0097] Example 4

[0098] A method for preventing groundwater leakage in a waste treatment plant differs from Example 1 in that serpentine powder is not added during the pretreatment of modified zeolite.

[0099] Example 5

[0100] A method for preventing groundwater leakage in a waste treatment plant differs from Example 1 in that wood vinegar is not added during the pretreatment of the modified zeolite.

[0101] Example 6

[0102] A method for preventing groundwater leakage in a waste treatment plant differs from Example 1 in that cetyltrimethylammonium bromide solution is not added during the pretreatment of modified zeolite.

[0103] Example 7

[0104] A method for preventing groundwater leakage in a waste treatment plant, which differs from Example 1 in that the modified attapulgite soil is prepared using Preparation Examples 1-2.

[0105] Example 8

[0106] A method for preventing groundwater leakage in a waste treatment plant, which differs from Example 1 in that the modified attapulgite soil is prepared using Preparation Examples 1-3.

[0107] Example 9

[0108] A method for preventing groundwater leakage in a waste treatment plant, which differs from Example 1 in that the modified attapulgite soil is prepared using Preparation Examples 1-4.

[0109] Example 10

[0110] A method for preventing groundwater leakage in a waste treatment plant, which differs from Example 1 in that the modified attapulgite soil is prepared using Preparation Examples 1-5.

[0111] Example 11

[0112] A method for preventing groundwater leakage in a waste treatment plant, which differs from Example 1 in that the modified attapulgite soil is prepared using Preparation Examples 1-6.

[0113] Example 12

[0114] A method for preventing groundwater leakage in a waste treatment plant, which differs from Example 1 in that the modified polyethylene fiber layer is prepared using Preparation Example 2-2.

[0115] Example 13

[0116] A method for preventing groundwater leakage in a waste treatment plant, which differs from Example 1 in that the modified polyethylene fiber layer is prepared using Preparation Examples 2-3.

[0117] Example 14

[0118] A method for preventing groundwater leakage in a waste treatment plant, which differs from Example 1 in that the modified polyethylene fiber layer is prepared using Preparation Examples 2-4.

[0119] Example 15

[0120] A method for preventing groundwater leakage in a waste treatment plant, which differs from Example 1 in that the modified polyethylene fiber layer is prepared using Preparation Examples 2-5.

[0121] Comparative Example

[0122] Comparative Example 1

[0123] A method for preventing groundwater leakage in a waste treatment plant differs from Example 1 in that, in the modified clay, the modified attapulgite is replaced by an equal amount of attapulgite.

[0124] Comparative Example 2

[0125] A method for preventing groundwater leakage in a waste treatment plant differs from Example 1 in that, in the modified clay, the modified zeolite is replaced by an equal amount of zeolite.

[0126] Comparative Example 3

[0127] A method for preventing groundwater leakage in a waste treatment plant differs from Example 1 in that, in the drainage network, the modified polyethylene fiber layer is replaced by an equal amount of polyethylene fiber layer.

[0128] Performance testing

[0129] The samples obtained by simulating the treatment methods of Examples 1-11 and Comparative Examples 1-2 were tested;

[0130] The 28-day permeability coefficient was tested using the method in GB / T50082-2009. The retention rate of pollutants in landfill leachate was tested using a permeameter with a sample diameter of 10 cm and a thickness of 3 cm. The retention rate was calculated by the difference in the amount of pollutants in the leachate before and after permeation of a unit length of sample.

[0131] The mechanical properties of the modified polyethylene fiber layers obtained in Examples 1, 12-15 and Comparative Example 3 were tested according to GB / T 40006.2-2021 standard, and the results are shown in Table 1.

[0132] Table 1 Test data for the examples and comparative examples

[0133]

[0134]

[0135] As can be seen from Table 1, Examples 1-2, 10, and 14 of this application all exhibit good anti-seepage and anti-leakage technical effects. Among them, the permeability coefficient K of Example 1 is 0.111 × 10⁻⁶. -8 The compressive strength is 65 MPa, and the unit length retention rate is 38.9% / cm for ammonia nitrogen, 36.9% / cm for Pb, 37.9% / cm for Hg, and 39.7% / cm for Cd. This indicates that the groundwater seepage prevention and control method for waste treatment plants proposed in this application has a good effect on preventing the discharge of landfill leachate. The prepared modified polyethylene fiber layer has good mechanical properties, with a tensile strength of 20 MPa and an elongation at break of 243%. It has good long-term usability when subsequently applied to drainage networks.

[0136] Example 3: By changing the amount of each raw material in the modified clay, as shown in Table 1, the permeability coefficient, compressive strength, and unit length resistance rate all decreased to varying degrees. This indicates that a treatment method with good seepage prevention effect can be obtained by mixing each raw material component in a certain ratio. Even when the mass ratio of each raw material component is not within a certain range, it still has a good seepage prevention effect.

[0137] In Example 4, no serpentine powder was added during the pretreatment of the modified zeolite; in Example 5, no wood vinegar was added during the pretreatment of the modified zeolite; and in Example 6, no hexadecyltrimethylammonium bromide solution was added during the pretreatment of the modified zeolite. Table 1 shows that the permeability coefficient, compressive strength, and resistance per unit length all decreased significantly. This indicates that the wood vinegar eroded the surface of the natural zeolite to a certain extent, increasing its specific surface area and facilitating the loading of subsequent components. Therefore, the absence of wood vinegar has a certain impact on the performance of the modified zeolite. Hexadecyltrimethylammonium bromide solution can activate the surface of the natural zeolite, further expanding its porosity and thus affecting its performance, which in turn affects the performance of the modified zeolite. Serpentine powder has heat resistance, corrosion resistance, and wear resistance, and can be loaded onto the surface of the natural zeolite, increasing its mechanical properties, bactericidal properties, and adsorption properties. This facilitates the loading of the modified zeolite with other components and further modifies the clay.

[0138] In Example 7, the preparation method of modified attapulgite soil does not include step (1). As shown in Table 1, the permeability coefficient K is 0.987 × 10⁻⁶. -8 The compressive strength was 55 MPa, and the unit length retention rate was 30.1% / cm for ammonia nitrogen, 29.5% / cm for Pb, 30.2% / cm for Hg, and 31.4% / cm for Cd. This indicates that oxalic acid erodes the surface of attapulgite to a certain extent, making the surface rough. Further calcination increases the specific surface area of ​​attapulgite, which in turn affects the subsequent load on the attapulgite and thus its modification properties.

[0139] In Example 8, the preparation method of modified attapulgite did not include straw fiber, and in Example 9, the preparation method of modified attapulgite did not include nano-titanium dioxide. As shown in Table 1, the permeability coefficient, compressive strength, and unit length retention rate all decreased significantly. This indicates that there are a large number of grooves on the surface of straw fiber. The nano-titanium dioxide is loaded in the grooves of straw fiber, which increases the mechanical properties of straw fiber. The straw fiber is loaded on the surface of attapulgite, which further increases the specific surface area of ​​attapulgite, thereby improving the adsorption capacity of attapulgite.

[0140] Example 11 changed the mass ratio of attapulgite, straw fiber, and nano-titanium dioxide. As shown in Table 1, the test data of permeability coefficient, compressive strength, and unit length retention rate were significantly better than those of Examples 8-9, but worse than those of Examples 1 and 10. This indicates that there is a synergistic effect between attapulgite, straw fiber, and nano-titanium dioxide. The nano-titanium dioxide is loaded on the surface of the straw fiber, and the straw fiber is loaded on the surface of the attapulgite, which further improves the adhesion, mechanical properties, and adsorption properties of the attapulgite, which is helpful for subsequent seepage prevention and leakage prevention treatment.

[0141] In Example 12, the modified polyethylene fiber layer was prepared without the addition of carbon nanotubes. As shown in Table 1, the tensile strength was 15 MPa and the elongation at break was 210%, indicating that carbon nanotubes have a very high surface area ratio and good mechanical properties, which in turn affect the mechanical properties of the modified polyethylene fiber layer. In Example 13, the modified polyethylene fiber layer was prepared without the addition of chitosan. As shown in Table 1, the tensile strength was 16 MPa and the elongation at break was 220%, indicating that chitosan coats the carbon nanotubes and the polyethylene layer material, further increasing the adhesion of carbon nanotubes to the surface of the polyethylene layer material, thereby improving the mechanical properties of the system.

[0142] Example 15 changed the mass ratio of polyethylene, carbon nanotubes and chitosan. As shown in Table 1, the tensile strength was 17 MPa and the elongation at break was 225%, indicating that there is a synergistic effect among polyethylene, carbon nanotubes and chitosan. Carbon nanofibers have excellent mechanical properties. Carbon nanofibers are loaded on the surface of polyethylene, and chitosan coats the polyethylene, further increasing the connectivity between carbon nanotubes and polyethylene, thereby improving the mechanical properties and other corresponding properties of polyethylene.

[0143] In Comparative Example 1, the modified attapulgite was replaced by an equal amount of attapulgite. Table 1 shows that the permeability coefficient K is 5.654 × 10⁻⁶. -8 The compressive strength is 43 MPa, and the unit length retention rate is 20.1% / cm for ammonia nitrogen, 19.4% / cm for Pb, 21.3% / cm for Hg, and 21.4% / cm for Cd. This indicates that the modified attapulgite in this application has excellent adsorption properties and will have good seepage prevention and leakage prevention performance when subsequently applied to modified clay.

[0144] In Comparative Example 2, the modified clay was replaced by an equal amount of zeolite. Table 1 shows that the permeability coefficient K was 5.521 × 10⁻⁶. -8 The compressive strength is 45 MPa, and the unit length retention rate is 21.1% / cm for ammonia nitrogen, 20.1% / cm for Pb, 21.5% / cm for Hg, and 21.6% / cm for Cd. This indicates that the zeolite modified in this application has superior mechanical properties, bactericidal properties, and adsorption properties, which will help the subsequent modified zeolite to load other components and further modify the clay.

[0145] In Comparative Example 3, the modified polyethylene fiber layer was replaced by an equal amount of polyethylene fiber layer in the drainage net. As shown in Table 1, the tensile strength was 10 MPa and the elongation at break was 195%, indicating that the modified polyethylene fiber layer prepared in this application has superior mechanical properties and can be used in the drainage net for a long time.

[0146] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for groundwater seepage control in a waste treatment plant, characterized in that, It comprises the following steps: (1) laying an exhaust layer on the upper side of the garbage pile, the exhaust layer is composed of gravel with a particle size of 25-50mm, the thickness of the exhaust layer is 30-40cm; (2) laying an under-film protection layer on the upper side of the exhaust layer, the under-film protection layer is composed of modified clay; (3) laying an HDPE geomembrane on the upper side of the under-film protection layer, the thickness of the HDPE geomembrane is 1.5-2mm, laying an over-film protection layer on the upper side of the HDPE geomembrane, the over-film protection layer is a three-dimensional composite drainage net; (4) laying a drainage layer on the upper side of the over-film protection layer, the drainage layer is composed of gravel with a particle size of 20-30mm, the thickness of the drainage layer is 20-30cm; (5) laying a green soil layer on the upper side of the drainage layer, the thickness of the green soil layer is 16-20cm, and the preparation is completed; The raw material components of the modified clay include modified attapulgite, sodium carboxymethyl cellulose, modified zeolite, betaine, polyvinyl alcohol, deionized water, defoaming agent and water reducing agent; The modified clay comprises the following raw material components by weight: modified attapulgite 50-60 parts, sodium carboxymethyl cellulose 10-15 parts, modified zeolite 15-30 parts, betaine 5-10 parts, polyvinyl alcohol 20-30 parts, deionized water 75-85 parts, defoaming agent 1-5 parts and water reducing agent 2-6 parts; The preparation method of the modified attapulgite comprises the following steps: (1) crushing and grinding attapulgite, then dispersing it in oxalic acid solution, stirring at 60-70℃ for 2-3h, filtering, and calcining at a temperature of 350-380℃ for 1-2h to obtain pretreated attapulgite; (2) dispersing straw fibers in anhydrous ethanol, then adding nano titanium dioxide, ultrasonicating for 1-3h, filtering, and drying to obtain modified straw fibers; (3) dispersing the pretreated attapulgite in deionized water, then adding the modified straw fibers, stirring at a temperature of 80-90℃ for 2-3h, and then adding xanthan gum to continue stirring to obtain modified attapulgite; The modified zeolite is pretreated by the following method: dispersing natural zeolite in wood vinegar solution, stirring for 1-3h, filtering, then adding into a cetyltrimethylammonium bromide solution, adding serpentine powder, stirring uniformly, filtering, and drying to obtain the modified zeolite.

2. The method for preventing groundwater leakage in a landfill site according to claim 1, wherein The mass ratio of the attapulgite, straw fibers and nano titanium dioxide is 1:0.1-0.3:0.05-0.

08.

3. The method for preventing groundwater leakage in a landfill site according to claim 1, wherein The defoaming agent is selected from one or more of fatty alcohol polyoxyethylene ether, liquid paraffin and polyether.

4. The method for preventing groundwater leakage in a landfill site according to claim 1, wherein The water reducing agent is a polycarboxylic acid type water reducing agent and / or a naphthalene type water reducing agent.

5. The method for preventing groundwater leakage in a landfill site according to claim 1, wherein The drainage net comprises a modified polyethylene fiber layer, a polyethylene interlayer and a geotextile layer; The preparation method of the modified polyethylene fiber layer comprises the following steps: (1) mixing polyethylene, bamboo nanofibers, cotton fibers, ethylene glycol and basalt fibers, stirring at a temperature of 90-95℃ for 3-5h, then adding a compatibilizer and an antioxidant, stirring uniformly, and then melting and mixing, extruding, cooling, granulating and drying to obtain a polyethylene layer material; (2) dispersing the carbon nanotube in deionized water, then adding acetic acid solution, stirring for 1-2 hours, then adding chitosan and polyethylene layer material obtained in step (1), and then performing hot pressing to obtain the modified polyethylene fiber layer.

6. The method for preventing groundwater leakage in a landfill site according to claim 5, wherein The mass ratio of the polyethylene, the carbon nanotube and the chitosan is 1:0.3-0.6:0.02-0.

05.

7. The method for preventing groundwater leakage in a landfill site according to claim 5, wherein The preparation method of the drainage net comprises the following steps: coating one side of the modified polyethylene fiber layer with an epoxy resin adhesive, then bonding the one side of the polyethylene interlayer, coating the side of the polyethylene interlayer away from the modified polyethylene fiber layer with an epoxy resin adhesive, then bonding the geotextile layer, and obtaining the drainage net.

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