Barrier wall-permeable reactive wall combination structure suitable for deep groundwater purification

Abstract

The present invention discloses a barrier wall-permeable reaction wall combination structure suitable for deep groundwater purification. A low-permeability barrier wall is arranged at the downstream groundwater outlet of a landfill, and a permeable reaction wall is arranged on the upper part of the middle section of the low-permeability barrier wall. The low-permeability barrier wall is formed by filling with low-permeability barrier wall materials such as soil-bentonite, cement-bentonite or grouting curtain; the section below the water level of the permeable reaction wall is filled with reactive fillers such as activated carbon, limestone or zeolite, and pollutants in the groundwater are removed by the reactive fillers; the section above the water level of the permeable reaction wall is filled with non-reactive fillers such as coarse sand or gravel. The present invention can solve the problems of large excavation depth, high construction cost and low filler utilization rate in the traditional permeable reaction wall structure for purifying deep contaminated groundwater, and can effectively purify target pollutants such as COD, ammonia nitrogen and heavy metals in deep contaminated groundwater.

Description

Technical Field

[0001] The present invention belongs to the technical field of groundwater pollution control and remediation at contaminated sites and relates to a combined structure for purifying deep groundwater pollution plumes, in particular to a barrier wall-permeable reaction wall combined structure suitable for deep groundwater purification. Background Art

[0002] my country has a large number of municipal solid waste landfills, resulting in high pollution loads and high leachate levels. The problem of bottom liner failure is particularly serious, and leachate leakage is a frequent occurrence. According to a 2018 survey by the Ministry of Housing and Urban-Rural Development, approximately 1,600 landfills and 27,000 simple landfills in China are at risk of leachate leakage. High-concentration leachate can seriously pollute surrounding surface water, groundwater, and soil, impacting human health and ecological safety. Valley-type landfills utilize natural mountain formations to create storage capacity, reducing the cost of excavation to increase storage capacity. However, valley-type sites have highly variable topography and deep groundwater depths. Typically, the groundwater dip is ≥15° and the hydraulic gradient is >0.02. These hydrodynamic conditions are more complex than those of plain and terraced landfills, posing a higher risk of groundwater contamination. Some valley-type landfills in my country continue to generate low-concentration wastewater even after closure, resulting in high operating costs and the need for disposal measures.

[0003] Permeable reactive wall technology is widely considered a sustainable in-situ remediation method for contaminated groundwater. The principle behind this technology is to install a permeable reactive wall downstream of a contaminated site, perpendicular to the groundwater flow direction. This allows contaminated groundwater to flow through the reaction zone within the wall, where the filler within the wall reacts with the contaminants physically and chemically, reducing the contaminants to the target remediation concentration. Its advantages include passive in-situ remediation, readily available and low-cost filler, low ongoing maintenance costs, and environmental sustainability. The structural selection of a permeable reactive wall requires comprehensive consideration of the site's hydrogeological characteristics and the distribution of the contamination plume, aiming to intercept the contamination plume as much as possible while achieving cost-effective purification. Permeable reactive wall structures primarily include continuous wall, water-blocking funnel-gate, passive collection belt reaction unit, and injection treatment belt. However, when the contamination plume is large and the groundwater and bedrock are deep, traditional permeable reactive wall structures present significant challenges in excavation and support, significantly increasing construction costs. Furthermore, uneven distribution of the contamination plume concentration leads to low utilization of the reactive filler within the wall.

[0004] Pilot trials or demonstration projects involving permeable reactive wall technology have been conducted at some sites in China, but these have so far only employed permeable reactive walls embedded in a relatively impermeable layer or constructed as impermeable units. Further development is needed to apply this technology to remediation projects involving deep contaminated groundwater at landfills. In 2012, Tian Lei et al. constructed a 5-meter-high underground concrete reaction tank in Jiaozuo, Henan Province, for pilot trials of trichloroethylene and toluene remediation in groundwater. In 2015, Teng Ying et al. employed a 10-11-meter-deep injection reaction system combined with a impermeable wall to remediate sulfate in tailings pond groundwater in Baotou, Inner Mongolia. In 2018, Song Xin et al. employed a 15-meter-deep permeable reactive wall to remediate groundwater contaminated by a chromium salt plant in Changsha, Hunan Province.

[0005] In addition, there are several patent reports in China regarding permeable reactive walls, a few of which combine hydraulic barriers with passive flow collection structures (Zheng Kaixuan et al., CN113896273A; Yang Qifeng et al., CN111153529A), some using externally driven flow collection structures (Pu Shengyan et al., CN115636464A; Zhu Zongqiang et al., CN113751493A), and some involving combined passive and externally driven flow collection (Wu Daishe et al., CN107311286A). However, there is currently no precedent in the prior art for using a low-permeability barrier wall-permeable reactive wall combination structure to purify and treat deep contaminated groundwater. Summary of the Invention

[0006] In response to the defects and problems existing in the background technology, the purpose of the present invention is to provide a barrier wall-permeable reaction wall combination structure suitable for deep groundwater purification, which is used to solve the problems of large excavation depth, great support difficulty, high construction cost and low filler utilization rate existing in the traditional permeable reaction wall purification of deep contaminated groundwater, and can effectively remove the main polluting components such as COD, ammonia nitrogen and heavy metals in contaminated groundwater.

[0007] The technical solutions adopted in the present invention are as follows:

[0008] The low permeability barrier wall-permeable reaction wall combination structure of the present invention is arranged at the downstream groundwater outlet of the landfill. The low permeability barrier wall-permeable reaction wall combination structure includes a low permeability barrier wall and a permeable reaction wall. The permeable reaction wall is arranged in the upper part of the middle of the low permeability barrier wall. The two sides of the low permeability barrier wall are respectively embedded in the mountains on both sides of the landfill. The upper surface of the permeable reaction wall is flush with the upper surface of the low permeability barrier wall. The permeable reaction wall and the low permeability barrier wall are both arranged perpendicular to the direction of groundwater flow. The low permeability barrier wall is mainly formed by filling low permeability anti-fouling materials, and the permeable reaction wall is mainly formed by layering non-reactive fillers and reactive fillers for purifying contaminated groundwater.

[0009] The non-reactive filler is filled in the area above the groundwater level of the permeable reaction wall, and the reactive filler is filled in the area below the groundwater level of the permeable reaction wall. The reactive filler is used to remove COD, ammonia nitrogen and heavy metals in the groundwater.

[0010] The non-reactive filler is one or more of coarse sand and gravel; the reactive filler is one or more of activated carbon, limestone and zeolite; the permeability coefficient of the non-reactive filler and the reactive filler is 1×10 -5 ~1×10 -3 m / s.

[0011] The low permeability antifouling material is made of soil-bentonite, cement-bentonite or grouting curtain. The permeability coefficient of the low permeability antifouling material is 1×10 -11 ~1×10 -9 m / s.

[0012] The downstream groundwater outflow of the landfill specifically refers to the downstream valley mouth of a valley-type landfill.

[0013] The low permeability barrier wall is embedded in the relative water-proof layer, and the thickness of the low permeability barrier wall is 0.6-1.2m.

[0014] The ratio of the depth of the low-permeability barrier wall to the depth of the permeable reaction wall is 6:1 to 10:1, the depth of the permeable reaction wall does not exceed 5m, and the thickness of the permeable reaction wall is 1.0 to 5.0m.

[0015] The thickness of low-permeability barrier walls is designed based on the performance of the barrier material, water head height, and the service life of the wall, and is generally 0.6 to 1.2 meters. The thickness of permeable reactive walls is designed based on the performance of the filler, the actual flow rate of the site, and pollutant information, and is generally 1.0 to 5.0 meters.

[0016] A low-permeability barrier wall is placed in the contaminated aquifer to prevent deep contaminated groundwater from flowing downstream, forcing the groundwater level to rise. Permeable reaction walls are installed in sections within the low-permeability barrier wall to allow the high-level groundwater to flow evenly through the permeable reaction wall.

[0017] A low-permeability barrier wall and permeable reactive wall combination is installed in situ at the downstream valley entrance of a valley-type landfill. The low-permeability barrier wall is embedded in the relative aquiclude, leaving a gap for the permeable reactive wall. This allows groundwater containing multi-component pollutants, intercepted by the low-permeability barrier wall, to overflow into the permeable reactive wall for purification and disposal via the reactive filler.

[0018] The present invention builds a low-permeability barrier wall at the downstream valley entrance of a valley-type landfill, raises the groundwater to the permeable reaction wall, and then uses the head difference to make the contaminated groundwater overflow into the permeable reaction wall under the action of driving force. In this way, the pollutants in the contaminated groundwater will fully react with the reactive filler to achieve purification.

[0019] This invention utilizes a low-permeability barrier wall to funnel contaminated groundwater into a permeable reactive wall, preventing the plume from flowing downstream and causing contamination within the landfill. This allows for in-situ capture and purification of the plume. Furthermore, the elevated groundwater level created by the low-permeability barrier wall forces all contaminated groundwater to flow evenly through the permeable reactive wall for centralized treatment, rather than embedding the permeable reactive wall within a relatively impermeable layer to dispose of the unevenly distributed plume. This allows for optimized placement of the permeable reactive wall based on the site's actual total amount of seepage, eliminating the need to consider the impact of high-concentration seepage pathways. This passive treatment approach achieves in-situ purification of the landfill's groundwater plume.

[0020] The beneficial effects of the present invention are:

[0021] 1. The low-permeability barrier wall-permeable reaction wall combination structure of the present invention can solve the problem of deep groundwater pollution. The low-permeability barrier wall intercepts the pollution plume and introduces the deep contaminated groundwater into the permeable reaction wall for purification and disposal.

[0022] 2. The low-permeability barrier wall-permeable reaction wall combination structure of the present invention operates autonomously by relying on the hydraulic head difference. The hydraulic head difference drives the contaminated groundwater to continuously flow into the permeable reaction wall without the need for external force, and is easy to operate and maintain.

[0023] 3. In the low-permeability barrier wall-permeable reactive wall combination structure of the present invention, the uneven distribution of groundwater pollution plumes caused by natural attenuation becomes relatively uniform after Yonggao, which prolongs the breakdown time of reactive fillers, realizes efficient utilization of fillers and efficient purification of polluted water.

[0024] In summary, the low-permeability barrier wall-permeable reactive wall combination structure of the present invention allows contaminated groundwater to passively rise and evenly pass through the permeable reactive wall, allowing pollutants and filler to fully react, significantly improving filler utilization and the wall's efficiency in purifying pollutants. The active filler material can be adjusted according to the target pollutants, achieving functions such as oxidation, precipitation, and adsorption, effectively purifying multi-component pollutants in contaminated groundwater. This invention offers advantages such as low construction cost, high filler utilization, strong design flexibility, easy operation and maintenance, and environmental sustainability, making it highly promising for widespread application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic plan view of the low permeability barrier wall-permeable reaction wall combined structure;

[0026] Figure 2 Schematic diagram of the cross section of the low permeability barrier wall-permeable reactive wall combined structure at AA;

[0027] Figure 3 This is a numerical simulation particle tracking effect diagram of the combined structure in the embodiment in the XY plane;

[0028] Figure 4 This is a particle tracking effect diagram of the numerical simulation of the combined structure in three-dimensional space in the embodiment.

[0029] In the figure: 1. Low-permeability barrier wall; 2. Permeable reactive wall; 3. Low-permeability anti-fouling material; 4. Non-reactive filler; 5. Reactive filler; 6. Initial groundwater level of the site; 7. Groundwater level after Yonggao; 8. Valley mouth boundary line of the valley-type landfill; 9. Particle tracking streamlines. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the embodiments.

[0031] The low permeability barrier wall-permeable reaction wall combination structure of the present invention is arranged at the downstream groundwater outlet of the landfill. The low permeability barrier wall-permeable reaction wall combination structure includes a low permeability barrier wall 1 and a permeable reaction wall 2. The permeable reaction wall 2 is arranged in the upper part of the middle of the low permeability barrier wall 1. The upper surface of the permeable reaction wall 2 is flush with the upper surface of the low permeability barrier wall 1. The permeable reaction wall 2 and the low permeability barrier wall 1 are both arranged perpendicular to the direction of groundwater flow; the low permeability barrier wall 1 is mainly formed by filling low permeability anti-fouling material 3, and the permeable reaction wall 2 is mainly formed by layered filling of non-reactive filler 4 and reactive filler 5 for purifying contaminated groundwater.

[0032] The non-reactive filler 4 is filled in the area above the groundwater level of the permeable reaction wall 2, and the reactive filler 5 is filled in the area below the groundwater level of the permeable reaction wall 2. The reactive filler 5 is used to remove pollutants such as COD, ammonia nitrogen and heavy metals in the groundwater.

[0033] The non-reactive filler 4 is one or more of coarse sand and gravel; the reactive filler 5 is one or more of activated carbon, limestone and zeolite; the permeability coefficients of the non-reactive filler 4 and the reactive filler 5 are both 1×10 -5 ~1×10 -3 m / s.

[0034] The low permeability barrier wall 1 is specifically a barrier wall filled with low permeability antifouling material. The low permeability antifouling material 3 is made of low permeability materials such as soil-bentonite, cement-bentonite or grouting curtain. The permeability coefficient of the low permeability antifouling material 3 is 1×10-11 ~1×10 -9 m / s.

[0035] The downstream groundwater outflow of the landfill specifically refers to the downstream valley mouth of the valley-type landfill.

[0036] The low permeability barrier wall 1 is embedded in the relative impermeable layer, and the thickness of the low permeability barrier wall 1 is 0.6-1.2 m.

[0037] The ratio of the depth of the low permeability barrier wall 1 to the depth of the permeable reaction wall 2 is 6:1 to 10:1, the depth of the permeable reaction wall (2) should not exceed 5m, and the thickness of the permeable reaction wall 2 is 1.0 to 5.0m.

[0038] The depth of the permeable reactive wall should not exceed 5m. If it is greater than 5m, support is required.

[0039] Both the low-permeability barrier wall and the permeable reactive wall are higher than the groundwater level after Yonggao. Reactive fillers are filled below the water level of the permeable reactive wall to purify contaminated groundwater, while non-reactive fillers are filled above the water level, making the upper surfaces of the low-permeability barrier wall and the permeable reactive wall flush, increasing the overall stability and strength of the structure, and preventing the upper part of the permeable reactive wall from being damaged due to stress concentration, which would affect the service life of the low-permeability barrier wall-permeable reactive wall combination structure.

[0040] In contaminated aquifers at valley-type landfills with large hydraulic gradients, low-permeability barrier walls are installed at the downstream valley mouth to block contaminated groundwater from flowing downstream.

[0041] The low-permeability barrier wall 1 penetrates weathered layers, fractured rock layers and other strata where seepage may occur, and is embedded in the underground relative impermeable layer 0.5 to 1.0 m. If the bedrock cracks at the bottom of the contaminated site are relatively developed, grouting and sealing measures must be adopted within a certain range at the bottom of the low-permeability barrier wall 1 to reduce permeability and prevent groundwater from flowing around the wall or the bottom, forcing the groundwater to stagnate.

[0042] The low-permeability barrier wall 1 captures the contaminated groundwater and raises it to the setting height of the permeable reaction wall 2. When water flows out of the permeable reaction wall 2, the water head upstream of the low-permeability barrier wall 1 is lower than the water head of the surrounding contaminated groundwater, resulting in a head difference. The head difference drives the contaminated groundwater around the low-permeability barrier wall 1 to flow evenly through the permeable reaction wall 2, reducing the size of the pollution plume and making the concentration distribution uniform, thereby improving the purification and disposal efficiency of the permeable reaction wall. There is no bypass of the contaminated groundwater, and efficient capture of downstream groundwater can be achieved.

[0043] like Figure 1As shown in the figure, the low permeability barrier wall-permeable reaction wall combination structure is arranged at the downstream valley mouth of the valley-type landfill. The downstream valley mouth specifically refers to the only downstream outflow under the condition that the surrounding mountains of the valley-type landfill form a natural water-isolating boundary. Figure 1 The solid arrow indicates the direction of the contaminated plume. The low-permeability barrier wall-permeable reactive wall composite structure comprises low-permeability barrier wall 1 and permeable reactive wall 2. During the construction of low-permeability barrier wall 1, a gap was reserved for permeable reactive wall 2. The two walls work synergistically, and the order of their construction cannot be omitted or interchanged.

[0044] The low permeability barrier wall 1 is formed by filling with low permeability anti-fouling materials 3 such as soil-bentonite, cement-bentonite or grouting curtain. After the construction, the groundwater level 7 upstream of the wall is higher than the initial groundwater level 6 of the site before construction.

[0045] The permeable reactive wall 2 is formed by filling at least one reactive filler 5, such as activated carbon, limestone, or zeolite, with a non-reactive filler 4, such as coarse sand or gravel. Depending on the target pollutant, the reactive filler 5 is selected to purify the groundwater by adsorption, precipitation, or oxidation. For example, if ammonia nitrogen and heavy metals are the primary components exceeding standards in the contaminated groundwater, a mixture of zeolite and activated carbon can be used as the reactive filler 5.

[0046] The low-permeability barrier wall-permeable reaction wall combination structure is arranged at 8 valley boundary lines of the valley-type landfill and embedded to a certain depth in the mountains on both sides of the landfill to improve the efficiency of capturing low-concentration contaminated groundwater downstream.

[0047] In the permeable reactive wall 2, if multiple types of fillers are involved, each vertical wall layer is arranged adjacent to each other in sequence.

[0048] With this arrangement, except for the permeable reaction wall 2 in the middle and upper part, the rest of the wall is made of low-permeability barrier wall 1. This causes the groundwater level to continuously rise, and the head difference drives the contaminated groundwater to overflow into the permeable reaction wall, where it can be smoothly purified and flow downstream.

[0049] The embodiments of the present invention are as follows:

[0050] A domestic waste landfill in Zhejiang Province, my country, mainly exposes Paleozoic clastic rock strata and Quaternary Middle and Holocene strata, with an aquifer thickness of about 45 to 50 meters.

[0051] The low-permeability barrier wall-permeable reaction wall combination structure is located at the downstream valley mouth of the valley-type landfill, with a hydraulic gradient of approximately 0.023 and a lateral distance of approximately 208m from the downstream valley mouth. According to the groundwater level and water volume at the site, the initial groundwater level and the groundwater level after Yonggao can be determined. Combined with the width of the groundwater pollution plume and the total amount of target pollutants, the dimensions of the low-permeability barrier wall 1 and the permeable reaction wall 2 are designed. The length L1 of the low-permeability barrier wall 1 is 210m, and the bottom of the low-permeability barrier wall 1 is embedded in a relative impermeable layer. The depth H1 of the low-permeability barrier wall 1 is 48m, and the thickness T1 is designed to be 0.6m. The length L2 of the permeable reaction wall 2 is 40m, the depth H2 is 5m, and the thickness T2 is 2m;

[0052] In practice, the pouring process for the low-permeability barrier wall (1) involves constructing a guide wall, preparing slurry, excavating a trench, retaining the slurry, backfilling with wall materials, and cleaning the top cover. A gap is reserved in the middle section based on the dimensions of the permeable reactive wall (2). The filler for the permeable reactive wall (2) can be loaded into prefabricated cubic steel cages, facilitating stacking, lifting, and replacement while preventing filler loss. After the low-permeability barrier wall-permeable reactive wall structure is filled, the soil layer is applied to the original elevation, and the surface is covered with greenery.

[0053] Using the groundwater flow module in Visual MODFLOW to simulate, the water discharge at the downstream boundary of the landfill is about 140m 3 / day. The main pollutants in the permeable reaction wall 2 and its upstream area are ammonia nitrogen (concentration ≤ 500mg / L) and manganese (concentration ≤ 3.1mg / L). Referring to the groundwater Class V standard, the maximum width of the pollution plume is about 100m. The permeable reaction wall 2 below the water level is filled with a mixed filler of zeolite and activated carbon with a particle size of 2.0-3.0mm, and above the water level is filled with coarse sand with a particle size greater than 0.5mm. The layout is as follows: Figure 1 and Figure 2 shown.

[0054] Adsorption reactions primarily occur within permeable reaction wall 2. Zeolite absorbs ammonia nitrogen and heavy metals through ion exchange, while coconut shell activated carbon physically adsorbs target pollutants through its large surface area and multi-level pore structure. The functional groups on the coconut shell activated carbon's surface also complex with pollutants to remove them.

[0055] The permeability coefficient of the filler in the permeable reactive wall 2 is about 10 -4 m / s. Under the condition of natural seepage field, the groundwater flow velocity in the permeable reaction wall 2 can reach up to 0.2m / d. When the downstream permeable water flow section is reduced to 19.2% of the original section, the actual groundwater flow velocity will increase to 5.2 times the original flow velocity, and the permeable reaction wall 2 will realize gravity flow driven by the head difference.

[0056] When the thickness T2 of the permeable reactive wall 2 is 2m, the cross section in the permeable reactive wall 2 (length L2 is 40m, depth H2 is 5m, thickness T2 is 2m) can generate a maximum of 208m 3 A flow rate of / d can achieve sufficient capture of the groundwater contamination plume upstream of the permeable reaction wall 2.

[0057] The particle tracking module in VisualMODFLOW was used to generalize the flow path of groundwater flowing through the "low permeability barrier wall-permeable reaction wall" in the example. The permeability coefficient of the aquifer is 10 -6 m / s, and the east and west boundaries are set as the upstream and downstream constant head boundaries respectively. Tracking particles are set at the upstream boundary, and the simulation calculation results in the XY plane and three-dimensional space are as follows: Figure 3 and Figure 4 As shown in the figure, the permeable reaction wall 2 has a significant flow collection effect due to the high permeability of its filler. The streamline distribution in the middle area is relatively uniform. The closer to the junction of the low permeability barrier wall and the permeable reaction wall, the denser the streamlines, that is, the greater the flow rate.

[0058] The low permeability barrier wall-permeable reactive wall combined structure forces water to flow uniformly through the reactive filler 5, effectively improving filler utilization and pollution plume purification efficiency.

[0059] Comparative Example

[0060] Under the same case conditions, an ordinary continuous permeable reaction wall is set up at the downstream valley entrance of the valley-type landfill. To ensure that the downstream contaminated groundwater can flow through the permeable reaction wall for purification and disposal, the bottom of the wall must be embedded in the relative impermeable layer for at least 0.6m, and the depth H is set to 48m; the length is 1.2 to 1.5 times the width of the pollution plume, and the length L is set to 120m; the thickness T of the reaction wall is 2m. The total volume of the continuous permeable reaction wall in this comparative example is 11520m 3 , and the total volume of the low permeability barrier wall-permeable reaction wall combined structure of the embodiment is about 6340m 3 , the excavation volume of the comparative example is large, the construction cost is high, and the filler utilization rate is low.

[0061] The present invention adopts a combined structure of a large-area low-permeability barrier wall and a small-area permeable reaction wall, so that a large head difference is generated on both sides of the low-permeability barrier wall. The large head difference drives the contaminated groundwater into the permeable reaction wall without the need for external force and is easy to operate; and the contaminated groundwater can be concentrated in a small-area permeable reaction wall for filtration, and the uneven distribution of the groundwater pollution plume caused by natural attenuation becomes relatively uniform after it is elevated; on the premise of ensuring that the filler thickness of the permeable reaction wall matches the groundwater flow rate and the inflow pollutant concentration, and the decontamination capacity matches the total amount of target pollutants, that is, ensuring that the filler has sufficient reaction time and adsorption capacity with the target pollutants, the same filtration effect as the large-area permeable reaction wall can be achieved, while achieving efficient utilization of the filler and efficient purification of the contaminated water flow, effectively reducing the filtration cost of contaminated groundwater.

Claims

1. A barrier wall-permeable reaction wall combination structure suitable for deep groundwater purification, characterized by: The barrier wall-permeable reaction wall combination structure is arranged at the downstream groundwater outflow of the landfill. The barrier wall-permeable reaction wall combination structure includes a low-permeability barrier wall (1) and a permeable reaction wall (2). The permeable reaction wall (2) is arranged in the upper part of the middle of the low-permeability barrier wall (1). Both sides of the low-permeability barrier wall (1) are embedded in the mountains on both sides of the landfill. The upper surface of the permeable reaction wall (2) is flush with the upper surface of the low-permeability barrier wall (1). The permeable reaction wall (2) and the low-permeability barrier wall (1) are both arranged perpendicular to the flow direction of the groundwater. The low-permeability barrier wall (1) is mainly formed by filling with a low-permeability anti-fouling material (3). The permeable reaction wall (2) is mainly formed by layering a non-reactive filler (4) and a reactive filler (5) for purifying contaminated groundwater.

2. The barrier wall-permeable reaction wall combined structure suitable for deep groundwater purification according to claim 1, characterized in that: The non-reactive filler (4) is filled in the area above the groundwater level of the permeable reaction wall (2), and the reactive filler (5) is filled in the area below the groundwater level of the permeable reaction wall (2). The reactive filler (5) is used to remove COD, ammonia nitrogen and heavy metals in the groundwater.

3. The barrier wall-permeable reaction wall combined structure suitable for deep groundwater purification according to claim 1, characterized in that: The non-reactive filler (4) is one or more of coarse sand and gravel; the reactive filler (5) is one or more of activated carbon, limestone and zeolite; The permeability coefficients of the non-reactive filler (4) and the reactive filler (5) are both 1×10 -5 ~1×10 -3 m / s.

4. The barrier wall-permeable reaction wall combined structure suitable for deep groundwater purification according to claim 1, characterized in that: The low permeability antifouling material (3) is made of soil-bentonite or cement-bentonite; The permeability coefficient of the low permeability antifouling material (3) is 1×10 -11 ~1×10 -9 m / s.

5. The barrier wall-permeable reaction wall combined structure suitable for deep groundwater purification according to claim 1, characterized in that: The downstream groundwater outflow outlet of the landfill specifically refers to the downstream valley mouth of a valley-type landfill.

6. The barrier wall-permeable reaction wall combined structure suitable for deep groundwater purification according to claim 1, characterized in that: The low permeability barrier wall (1) is embedded in the relative water-repellent layer, and the thickness of the low permeability barrier wall (1) is 0.6-1.2 m.

7. The barrier wall-permeable reaction wall combined structure suitable for deep groundwater purification according to claim 1, characterized in that: The ratio of the depth of the low permeability barrier wall (1) to the depth of the permeable reaction wall (2) is 6:1 to 10:1, the depth of the permeable reaction wall (2) does not exceed 5 m, and the thickness of the permeable reaction wall (2) is 1.0 to 5.0 m.

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