A method for accelerating aerobic stabilization of a landfill

Abstract

The application provides a method for accelerating aerobic stabilization of a landfill, and belongs to the technical field of landfill treatment, and comprises the following steps: arranging a leachate recharge well in a garbage layer and arranging two water injection pipes with different positions in the leachate recharge well; covering the garbage layer; and respectively adding leachate with different microbial compound inoculants into the water injection pipes with different positions. The method provided by the application can shorten the degradation time of organic matters in the garbage, accelerate the stabilization of the garbage, and reduce the operation cost of the stabilization.

Description

Technical Field

[0001] This invention relates to the field of landfill remediation technology, and in particular to a method for accelerating the aerobic stabilization of landfills. Background Technology

[0002] Currently, there are a large number of informal landfills in my country. These informal landfills fail to meet the requirements of sanitary landfill technical specifications and standards, and fail to cover the landfills in a timely manner or properly dispose of pollutants such as leachate and landfill gas. This results in serious environmental pollution, which manifests as pollution of surface water and groundwater, air pollution, encroachment on land resources, pollution of soil and farmland, and breeding of mosquitoes and flies that spread diseases.

[0003] Aerobic bioreactor technology for the remediation of informal landfills is a landfill management technology that has emerged in recent years. The basic principle is to treat the landfill as a large bioreactor, using methods such as forced ventilation, water injection, and leachate recharge to transform the anaerobic conditions within the landfill into an aerobic environment. Under suitable oxygen, temperature, and moisture conditions, organic waste in the landfill undergoes aerobic degradation, generating stable organic matter, inorganic matter, CO2, and water, reducing pollution to soil, atmosphere, and water, and accelerating the stabilization process of the landfill.

[0004] However, in practice, it has been found that leachate from informal landfills contains high concentrations of ammonia nitrogen. Repeated refilling of leachate leads to a continuous increase in ammonia nitrogen content, causing an imbalance in the C / N ratio of the landfill, which to some extent inhibits the aerobic fermentation process and slows down the stabilization process of the landfill. The limited variety and lack of specificity of the indigenous microorganisms in the waste also lead to unstable aerobic treatment effects and prolonged treatment cycles, thereby increasing the operation and management costs of the process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention creatively proposes a method for accelerating the aerobic stabilization of landfills. Through optimization of the selection and addition of microbial agents, the construction of leachate reinjection wells, and the method of landfill sealing, this method achieves excellent aerobic stabilization effects on landfills, especially informal landfills with high-concentration ammonia nitrogen leachate. Specifically:

[0006] A method for accelerating aerobic stabilization of landfills includes:

[0007] Step S1: Install leachate reinjection wells within the landfill layer;

[0008] Step S2: On the surface of the garbage layer outside the leachate reinjection well, from bottom to top, a lower layer of water-conducting filler, an upper layer of water-conducting filler, and a greening soil layer are formed in sequence.

[0009] Step S3: Insert the first water injection pipe and the second water injection pipe into the leachate reinjection well. The first water injection pipe is inserted to the upper layer of the water-conducting packing layer, and the second water injection pipe is inserted to the depth of the waste layer. At least a portion of the first water injection pipe located in the upper layer of the water-conducting packing layer and at least a portion of the second water injection pipe located in the waste layer are perforated pipes.

[0010] Step S4: Fill the leachate reinjection well with gravel to the upper surface of the water-conducting filler layer, and then fill the upper surface of the gravel with bentonite and red clay to the position of the leachate reinjection wellhead.

[0011] Step S5: Inject leachate containing microbial compound agent A into the first water injection pipe, and inject leachate containing microbial compound agent B into the second water injection pipe.

[0012] Optionally, in step S2, the upper layer of the water-conducting filler layer is composed of a mixture of cinder, ceramsite, and coarse sand in a mass ratio of 2:1:1; the lower layer of the water-conducting filler layer is a covering material made of bentonite, slow-release carbon source, gravel, and organic polymer, with a thickness of 5 cm. Specifically, when preparing the covering material, the organic polymer is formed into a liquid (e.g., dissolved in water), and then the gravel is moistened with the liquid organic polymer. Bentonite and slow-release carbon source are added sequentially and mixed to form the covering material. The gravel diameter is 6-10 mm, and the mass ratio of bentonite, slow-release carbon source, gravel, and organic polymer is 30%:3%:65%:2%. The organic polymer is selected from polyacrylamide, and the slow-release carbon source is selected from rice husks or sawdust.

[0013] Optionally, in step S2, nitrogen-fixing plants, such as ryegrass and legumes, are planted on the greening soil layer. Preferably, the upper surface of the greening soil layer is flush with the inlet of the leachate reinjection well.

[0014] Optionally, in step S3, the perforated portion of the first and second water injection pipes is a perforated opening or a slit-shaped opening; the diameter of the perforated opening is no greater than 6 mm, and the slit width of the slit-shaped opening is no greater than 1 mm; the open surface area of ​​the perforated pipe is between 25% and 30% of the perforated pipe area, and the perforated pipe is wrapped with geotextile.

[0015] Optionally, in step S3, the thickness of the upper layer of the water-conducting packing layer is 50cm, and the length of the perforated section of the first water injection pipe is 40cm; the length of the perforated section of the second water injection pipe is set according to the thickness of the garbage layer.

[0016] Optionally, in step S5, the microbial compound agent A is composed of solid microbial powders of Pseudomonas schlegelii, Pichia pastoris, Bacillus subtilis, and Halomonas.

[0017] *Pseudomonas schrenckii*, accession number CGMCC1.15316;

[0018] Pichia pastoris, preservation number CGMCC2.2179;

[0019] Bacillus subtilis, preservation number CGMCC1.7740;

[0020] Halomonas, preservation number CGMCC NO. 9941;

[0021] The preparation method of compound microbial agent A is as follows: after the four microbial agents are cultured separately, they are mixed in a mass ratio of 30% *Pseudomonas schrenckii*, 10% *Pichia pastoris*, 20% *Bacillus subtilis*, and 40% *Haloxylon ammodendron* to prepare a dried microbial agent.

[0022] Optionally, in step S5, the microbial compound agent B is composed of solid bacterial powders of Bacillus subtilis, Pichia pastoris, lactic acid bacteria, Phanerochaete chrysosporium, and Acidobacterium ferrooxidans.

[0023] Bacillus subtilis, preservation number CGMCC1.7740;

[0024] Pichia pastoris, preservation number CGMCC2.2179;

[0025] *Procambarus chrysosporus*, preservation number CGMCC3.7212;

[0026] Lactic acid bacteria, preservation number CGMCC No. 5959;

[0027] Thiobacillus ferrooxidans, accession number CGMCC NO.0727;

[0028] The preparation method of compound microbial agent B is as follows: after the five microbial agents are cultured separately, they are mixed in a mass ratio of 25% Bacillus subtilis, 15% Pichia pastoris, 45% lactic acid bacteria, 10% P. chrysophagus flavosus, and 5% thiobacillus ferrooxidans to prepare a dried microbial agent.

[0029] The beneficial effects of the technical solution provided by this invention include at least the following:

[0030] This invention can efficiently remove ammonia nitrogen from leachate and landfill by simultaneously utilizing plant absorption, filler adsorption, and microbial action. The fillers involved in this invention are diverse, can make full use of solid waste in the industrial field, are environmentally friendly, low-cost, and stable. According to the types of pollutants in aerobic treatment of landfills, this invention selectively adds different microbial compound agents in layers, utilizing the enhancing effect of exogenous functional microorganisms to improve the degradation efficiency of pollutants, enhance the removal of pollutants in leachate, reduce the difficulty of subsequent water treatment, shorten the remediation cycle, and reduce treatment costs. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a cross-sectional view of the leachate reinjection well according to the present invention;

[0033] Among them: 1-first water injection pipe, 2-second water injection pipe, 3-red clay, 4-leachate recharge well, 5-green soil layer, 6-upper layer of water-conducting filler, 7-lower layer of water-conducting filler, 8-garbage layer, 9-geotextile, 10-flower pipe, 11-gravel, 12-bentonite. Detailed Implementation

[0034] The technical solution of this invention is described below.

[0035] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0036] In this embodiment of the invention, sometimes a subscript such as W1 may be mistakenly written as a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0037] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0038] The present invention provides a method for optimizing and accelerating the aerobic stabilization of informal landfills, which includes: the selection and addition of microbial agents, the construction of leachate reinjection wells, and the method of landfill sealing and covering.

[0039] Two φ50mm water injection pipes are installed in the φ200mm leachate reinjection well 4, namely the first water injection pipe 1 and the second water injection pipe 2. The first water injection pipe 1 is used for reinjection of leachate with added microbial compound agent A, and the second water injection pipe 2 is used for reinjection of leachate with added microbial compound agent B.

[0040] The first water injection pipe 1 enters the upper layer 6 of the water-conducting filler layer as a perforated pipe. The depth of the water injection pipe 1 is determined by the green soil layer and the upper layer of the water-conducting filler layer, with the bottom of the pipe located 10cm above the bottom of the upper layer of the water-conducting filler layer. The second water injection pipe 2 enters the garbage layer 8 as a perforated pipe 10, the length of which is adjusted according to the actual thickness of the garbage layer. The perforated pipe 10 has perforated openings with a diameter not exceeding 6mm and an open surface area between 25% and 30%. It needs to be wrapped with 150g / m² material. 2 Geotextile 9. The perforated pipe 10 can also be replaced by a slotted pipe, with a slot width not exceeding 1mm. Gravel 11 with a particle size of 1~2mm is filled between the walls of the first water injection pipe 1, the second main water pipe 2 and the leachate reinjection well 4. The gravel 11 is backfilled to the top of the upper layer 6 of the water-conducting filler. Bentonite is first backfilled on the gravel 11 with a thickness of 10cm, and then red clay 3 is further backfilled to the top of the water injection well, so that it is on the same plane as the surrounding green soil layer.

[0041] The greening soil layer 5 is a layer of soil with a thickness of 20-30cm. Nitrogen-fixing plants, such as ryegrass, are preferred to be planted on the greening soil layer 5.

[0042] The water-conducting packing layer consists of an upper layer 6 and a lower layer 7. The upper layer 6 and the lower layer 7 are each composed of different materials. The upper layer 6 is composed of coal slag, ceramsite, and coarse sand with a mass ratio of 2:1:1 and a diameter of 2-4 mm, with a thickness of 50 cm. The lower layer 7 is a pre-synthesized covering material composed of bentonite, slow-release carbon source, gravel, and organic polymer, with a thickness of 5 cm.

[0043] The working process of this invention for accelerating the aerobic stabilization of informal landfills is as follows:

[0044] Moisture content in the landfill is a fundamental condition and the most important factor for ensuring aerobic operation. Based on the needs of aerobic remediation reactions in landfills, water (leachate or additional water) needs to be injected into the landfill to ensure favorable conditions for aerobic reactions. According to the monitoring of landfill landfill moisture, the leachate reinjection system automatically controls the start of the reinjection pump. Leachate with added microbial compound agent A is reinjected at a certain speed and flow rate through the first water injection pipe 1 into the upper layer 6 of the water-conducting packing layer. During the seepage of the leachate, some ammonia nitrogen, organic matter, and inorganic matter in the leachate are adsorbed onto the surface of the packing material. Some ammonia nitrogen, sulfate, and other inorganic matter are absorbed and utilized by plant roots, while some are degraded and transformed by the added compound agent through microbial action. Microbial compound agent A is mainly used to remove ammonia nitrogen and nitrate nitrogen from the leachate. The ammonia nitrogen adsorbed on the surface of the packing material is converted into nitrate under the action of microorganisms and then detaches from the surface, thus regenerating the adsorbed packing material. The lower layer 7 of the water-conducting packing layer expands upon hydrolysis in water, forming a uniform, adhesive, non-permeable, high-quality elastic layer that provides a nutrient substrate for microorganisms. The added slow-release carbon source is continuously and slowly released outwards, enabling the packing to effectively remove pollutants from the leachate over a long period, preventing pollutants and gases from escaping upwards from the landfill layer, and facilitating the collection of exhaust gases by the landfill's exhaust system. Simultaneously, the leachate reinjected with the added microbial compound agent B enters the landfill layer 8 through the second water injection pipe 2. Informal landfills are typically under anaerobic conditions, containing large amounts of H2S and difficult-to-degrade organic matter. This invention enhances biological activity by enriching the functional microbial species in the landfill, thereby improving waste degradation efficiency. In addition to decomposing organic matter, the compound agent B of this invention also consumes H2S and removes odors.

[0045] Example 1

[0046] The average concentration of ammonia nitrogen in the groundwater extracted from the area of ​​an informal landfill was 10 mg / L, while the average COD content in the leachate inside the landfill was 5620 mg / L, and the average ammonia nitrogen content was 392 mg / L. Based on the site survey results, 21 injection wells were designed with a depth of 5-10 m, and the well pipe diameter was 200 mm. All well pipes leading into the landfill waste were perforated pipes. Two injection pipes were installed in each injection well. The first injection pipe had a perforated pipe length of 65 cm, with micropores of 1 mm in diameter and an open surface area of ​​30% of the perforated pipe area. The length of the second injection pipe was determined according to the depth of the waste, ranging from 4.15 to 9.15 m, and the perforated pipe specifications were the same as the first injection pipe. The upper layer of the water-conducting filler is composed of a mixture of coal slag, ceramsite, and coarse sand with a particle size of 2-4 mm in a mass ratio of 2:1:1, with a thickness of 50 cm. The lower layer of the water-conducting filler is a covering material made of bentonite, rice husks, gravel, and polyacrylamide in a mass ratio of 30%:3%:65%:2%, with a thickness of 5 cm. After placing two water injection pipes in the injection well, 2 mm diameter gravel is backfilled to the top of the upper layer of the water-conducting filler. Then, 10 cm of bentonite is backfilled on the gravel layer, followed by red clay backfilling to the top of the injection well. The first water injection pipe is injected with a compound microbial agent composed of 30% *Pseudomonas schlegelii*, 10% *Pichia pastoris*, 20% *Bacillus subtilis*, and 40% *Haloxylon ammodendron* in a mass ratio of 1:5000, that is, 200 g of the agent is added for every 1 cubic meter of leachate re-injected. A compound microbial agent, prepared by mixing 25% Bacillus subtilis, 15% Pichia pastoris, 45% lactic acid bacteria, 10% P. chrysosporium spp., and 5% A. ferrooxidans by mass ratio, was injected through a long water injection pipe. The dosage of the compound microbial agent was 1:10000, meaning 100g of agent was added for every 1 cubic meter of leachate recharged. The entire leachate recharge system operated intermittently, with adjustments made based on data from the temperature and humidity monitoring system. A 0.3m thick soil cover layer was planted on top. After 5 months of operation, the planted ryegrass grew well, with most settlement points showing a settlement of 5-37mm, and some individual points showing a settlement as high as 159mm. Through continuous extraction and recharge of the landfill leachate, the fluctuation range of the landfill's moisture content decreased from 27.49%–51.05% to 37.25%–39.49%, resulting in a more uniform moisture content distribution, which is beneficial for aerobic reactions. The ammonia content in the groundwater at the monitoring point decreased to 0.44 mg / L, the ammonia nitrogen content in the leachate from the heap decreased to 34 mg / L, and the COD content decreased to 490 mg / L.

[0047] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for accelerating the aerobic stabilization of landfills, characterized in that, include: Step S1: Install leachate reinjection wells within the landfill layer; Step S2: On the surface of the landfill outside the leachate reinjection well, from bottom to top, a lower layer of water-conducting filler, an upper layer of water-conducting filler, and a greening soil layer are formed sequentially. Step S3: Insert the first water injection pipe and the second water injection pipe into the leachate reinjection well. The first water injection pipe is inserted to the upper layer of the water-conducting packing layer, and the second water injection pipe is inserted to the depth of the waste layer. At least a portion of the first water injection pipe located in the upper layer of the water-conducting packing layer and at least a portion of the second water injection pipe located in the waste layer are perforated pipes. Step S4: Fill the leachate reinjection well with gravel to the upper surface of the water-conducting filler layer, and then fill the upper surface of the gravel with bentonite and red clay to the position of the leachate reinjection wellhead. Step S5: Inject leachate containing microbial compound agent A into the first water injection pipe, and inject leachate containing microbial compound agent B into the second water injection pipe; In step S5, the microbial compound agent A is composed of solid microbial powders of Pseudomonas schlegelii, Pichia pastoris, Bacillus subtilis, and Halomonas. *Pseudomonas schrenckii*, accession number CGMCC1.15316; Pichia pastoris, preservation number CGMCC2.2179; Bacillus subtilis, preservation number CGMCC1.7740; Halomonas, preservation number CGMCC NO. 9941; The preparation method of compound microbial agent A is as follows: after the four microbial agents are cultured separately, they are mixed in a mass ratio of 30% Pseudomonas schrenckii, 10% Pichia pastoris, 20% Bacillus subtilis, and 40% Halomonas to prepare a dried microbial agent. In step S5, the microbial compound agent B is composed of solid bacterial powders of Bacillus subtilis, Pichia pastoris, lactic acid bacteria, Phanerochaete chrysosporium, and Acidobacterium ferrooxidans. Bacillus subtilis, preservation number CGMCC1.7740; Pichia pastoris, preservation number CGMCC2.2179; *Procambarus chrysosporus*, preservation number CGMCC3.7212; Lactic acid bacteria, preservation number CGMCC No. 5959; Thiobacillus ferrooxidans, accession number CGMCC NO.0727; The preparation method of the compound microbial agent is as follows: after the five microbial agents are cultured separately, they are mixed in a mass ratio of 25% Bacillus subtilis, 15% Pichia pastoris, 45% lactic acid bacteria, 10% P. chrysophagus flavosus, and 5% thiobacillus ferrooxidans to prepare a dried microbial agent.

2. The method according to claim 1, characterized in that, In step S2, the upper layer of the water-conducting filler layer is composed of a mixture of coal slag, ceramsite, and coarse sand in a mass ratio of 2:1:1; the lower layer of the water-conducting filler layer is a covering material made of bentonite, slow-release carbon source, gravel, and organic polymer, with a thickness of 5cm.

3. The method according to claim 1, characterized in that, In step S2, nitrogen-fixing plants are planted on the green soil layer.

4. The method according to claim 1, characterized in that, In step S3, the perforated part of the first and second water injection pipes has a hole-shaped opening or a slit-shaped opening; the diameter of the hole-shaped opening is no more than 6 mm, and the slit width of the slit-shaped opening is no more than 1 mm; the open surface area of ​​the perforated pipe is between 25% and 30%, and the perforated pipe is wrapped with geotextile.

5. The method according to claim 1, characterized in that, In step S3, the thickness of the upper layer of the water-conducting filler layer is 50cm, and the length of the perforated section of the first water injection pipe is 40cm; the length of the perforated section of the second water injection pipe is set according to the thickness of the garbage layer.

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