Groundwater treatment system

Abstract

The application provides a groundwater treatment system and relates to the technical field of environmental protection, and solves the technical problem that the removal effect of heavy metals in groundwater is poor due to the presence of nitrate at present. The groundwater treatment system comprises a nitrate removal unit and a first permeable reactive wall; wherein the nitrate removal unit is used for removing nitrate in a target contaminated area, the first permeable reactive wall is arranged downstream of the target contaminated area, and the first permeable reactive wall is filled with an iron-based material.

Description

Technical Field

[0001] This application relates to the field of environmental protection technology, and in particular to a groundwater treatment system. Background Technology

[0002] Permeable reactive barriers are a commonly used in-situ treatment technology for groundwater remediation. They use permeable barriers filled with reactive media to intercept and remediate groundwater. Filling the reactive barrier with iron-based materials to remove heavy metals is currently a frequently used method for treating heavy metal-contaminated groundwater.

[0003] For example, CN106315816A discloses a permeable reactive wall technology, which removes various heavy metal ions from wastewater by filling a permeable reactive wall with a mixture of zero-valent iron and zero-valent aluminum. As another example, CN111320216A discloses a groundwater heavy metal remediation reactive medium material, which treats groundwater contaminated with various heavy metals by filling a permeable reactive wall with a reactive medium comprising quartz sand, iron powder, and zeolite powder.

[0004] However, groundwater flowing through permeable reactive barriers often contains not only heavy metal ions but also nitrates. The inventors discovered that the presence of nitrates can easily deactivate the iron-based materials in the permeable reactive barrier, resulting in poor removal of heavy metals from the groundwater. Summary of the Invention

[0005] This application provides a groundwater treatment system that can solve the current technical problem that the presence of nitrates easily leads to poor removal of heavy metals from groundwater.

[0006] In a first aspect, embodiments of this application provide a groundwater treatment system, the groundwater treatment system including a nitrate removal unit and a first permeable reactive barrier;

[0007] The nitrate removal unit is used to remove nitrates from the target contaminated area. The first permeable reactive wall is located downstream of the target contaminated area and is filled with iron-based material.

[0008] Optionally, in one embodiment, the target contaminated area includes in-situ nitrate-reducing bacteria, and the nitrate removal unit includes a first delivery unit for delivering a nutrient solution to the target contaminated area to promote the growth and reproduction of the in-situ nitrate-reducing bacteria.

[0009] Optionally, in one embodiment, the system further includes an iodate removal unit for removing iodate from the target in-situ reaction zone, the target in-situ reaction zone being disposed between the target contaminated area and the first permeable reactive wall.

[0010] Optionally, in one embodiment, the nutrient solution includes a calcium salt solution, and the iodate removal unit includes a second delivery unit; the second delivery unit is used to deliver a carbonate solution to the target in-situ reaction region.

[0011] Optionally, in one embodiment, the first delivery unit includes a first injection well connecting the surface and groundwater, and the second delivery unit includes a second injection well connecting the surface and groundwater.

[0012] Optionally, in one embodiment, the system further includes a water filtration unit disposed between the target in-situ reaction zone and the first permeable reactive wall.

[0013] Optionally, in one embodiment, the system further includes a second permeable reactive wall disposed downstream of the first permeable reactive wall, the second permeable reactive wall being filled with a carbon-based adsorbent material.

[0014] Optionally, in one embodiment, the carbon-based adsorbent comprises Ag-based adsorbents. + Modified carbon-based materials.

[0015] Optionally, in one embodiment, the system further includes a water-proof unit disposed on top of the first permeable reactive wall and the second permeable reactive wall.

[0016] Optionally, in one embodiment, the first permeable reactive wall is further filled with clinoptilolite.

[0017] The beneficial effects of the embodiments in this application are as follows:

[0018] The groundwater treatment system provided in this application includes a nitrate removal unit and a first permeable reactive barrier. The nitrate removal unit removes nitrates from a target contaminated area. The first permeable reactive barrier is located downstream of the target contaminated area and is filled with an iron-based material. By removing nitrates from the target contaminated area upstream of the first permeable reactive barrier filled with iron-based material, the amount of nitrates flowing into the groundwater flowing towards the first permeable reactive barrier can be significantly reduced, thereby improving the removal efficiency of heavy metals from the groundwater. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0020] Figure 1 This is a schematic diagram of the structure of a groundwater treatment system provided in an embodiment of this application;

[0021] Figure 2 This is a schematic diagram of another groundwater treatment system provided in an embodiment of this application;

[0022] Figure 3 This is a schematic diagram of the structure of another groundwater treatment system provided in the embodiments of this application;

[0023] Figure 4 This is a schematic diagram of the structure of another groundwater treatment system provided in the embodiments of this application;

[0024] Figure 5 This is a schematic diagram of another groundwater treatment system provided in an embodiment of this application.

[0025] Figure label:

[0026] 10—Groundwater treatment system; 1011—Nutrient solution storage tank; 1012—First main pipeline; 1013—First branch pipeline; 1014—First flow meter; 102—First permeable reactive wall; 1031—Carbonate storage tank; 1032—Second main pipeline; 1033—Second branch pipeline; 1034—Second flow meter; 104—Water filtration unit; 105—Second permeable reactive wall; 106—Waterproof unit; 1061—Barrier hardening layer; 1062—Backfill layer. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] As described in the background section of this application, groundwater flowing through a permeable reactive barrier filled with iron-based materials often contains not only heavy metal ions but also nitrates. The inventors have discovered that the presence of nitrates can significantly impair the removal of heavy metals from groundwater. Nitrates affect the redox potential in the groundwater environment, thus impacting the reduction performance of the iron-based materials. Furthermore, the presence of nitrates can cause a passivation film to form on the surface of the iron-based materials (such as a passivated magnetite film on the surface of zero-valent iron), leading to the deactivation of the iron-based materials.

[0029] To address this, this application provides a groundwater treatment system 10, which can solve the aforementioned technical problem that the presence of nitrates easily leads to poor removal of heavy metals from groundwater. Specifically, as... Figure 1 As shown, the groundwater treatment system may include a nitrate removal unit and a first permeable reactive wall 102; the nitrate removal unit is used to remove nitrates from the target contaminated area A, and the first permeable reactive wall 102 is located downstream of the target contaminated area A, and the first permeable reactive wall 102 is filled with iron-based material.

[0030] The groundwater treatment system 10 can be used to treat various types of wastewater, including groundwater and surface water. For ease of explanation of the solutions provided in this application, the following description will primarily focus on groundwater as the object of treatment in the groundwater treatment system. In groundwater layers, groundwater often coexists with soil, flowing through pores in the soil.

[0031] When the target water is groundwater, the target contaminated area A can be an area with high nitrate content located upstream of the groundwater. There can be one or more target contaminated areas A. In practice, nitrate content can be tested in the water quality of each area upstream of the groundwater, and areas with nitrate concentrations greater than a preset threshold can be identified as target contaminated areas A. The preset threshold can be set according to actual conditions.

[0032] The first permeable reactive wall 102 is filled with an iron-based material, which can be used to remove heavy metals and organic matter from groundwater flowing through it. The iron-based material has reducing properties, which can remove heavy metals and organic matter by lowering their valence state and degrading organic matter. In practical applications, the iron-based material in the first permeable reactive wall 102 can also fix heavy metals and organic matter within the reactive wall through adsorption, precipitation, and other methods, thereby achieving the removal of heavy metals and organic matter.

[0033] The iron-based materials may include zero-valent iron and / or ferrous hydroxide; zero-valent iron may specifically include iron powder, iron filings, etc. The heavy metals that the first permeable reactive wall 102 can remove may include, but are not limited to, manganese, copper, zinc, arsenic, cadmium, and lead.

[0034] The nitrate removal unit can be used to remove nitrates from target contaminated area A. The nitrate removal unit can remove nitrates from target contaminated area A using chemical, biological, or other methods. In specific implementation, the specific structure and location of the nitrate removal unit can be tailored to the location of target contaminated area A and the specific method used to remove nitrates from target contaminated area A. For example, the nitrate removal unit corresponding to target contaminated area A in groundwater may differ from the nitrate removal unit corresponding to target contaminated area A in surface water.

[0035] In this embodiment, the first permeable reactive barrier 102 is located downstream of the target contaminated area A, which can be understood as the groundwater flowing from the target contaminated area A to the first permeable reactive barrier 102. Figure 1 The middle arrow can be used to indicate the direction of groundwater flow. In addition, while the groundwater in the target contaminated area A flows towards the first permeable reactive barrier 102, the groundwater in each area located upstream of the groundwater can also flow towards the first permeable reactive barrier 102.

[0036] Therefore, the solution provided in this application embodiment can be understood as follows: a first permeable reactive wall 102 is set up downstream of the underground water body, and a target contaminated area A is determined in the area upstream of the underground water body; groundwater in all areas upstream of the underground water body (including the target contaminated area A) flows towards the first permeable reactive wall 102. Under the action of the nitrate removal unit, the nitrate content in the target contaminated area A is greatly reduced, and the nitrate content in other areas upstream of the underground water body is also originally low, thereby greatly reducing the nitrate in the groundwater flowing towards the first permeable reactive wall 102.

[0037] It is understood that the groundwater treatment system 10 provided in this application includes a nitrate removal unit and a first permeable reactive barrier 102. The nitrate removal unit is used to remove nitrates from the target contaminated area A. The first permeable reactive barrier 102 is located downstream of the target contaminated area A and is filled with an iron-based material. By removing nitrates from the target contaminated area A upstream of the first permeable reactive barrier 102 filled with iron-based material, the amount of nitrates in the groundwater flowing towards the first permeable reactive barrier 102 can be greatly reduced, thereby improving the removal efficiency of heavy metals in the groundwater.

[0038] Furthermore, iron-based materials are typically filled into the first permeable reactive barrier 102 in the form of dispersed particles, with groundwater flowing through the pores between the particles. However, in the presence of nitrates, a passivation film easily forms on the surface of the iron-based material. Inevitably, multiple particles may be simultaneously encapsulated by the same passivation film, leading to particle agglomeration within the first permeable reactive barrier 102. This blockage of the first permeable reactive barrier 102 hinders groundwater flow and significantly shortens its service life. The solution provided in the above embodiments of this application, by removing nitrates from the target contaminated area A upstream of the first permeable reactive barrier 102 filled with iron-based material, significantly reduces the amount of nitrates in the groundwater flowing towards the first permeable reactive barrier 102. This reduces the formation of the passivation film, alleviates the blockage of the first permeable reactive barrier 102, and extends its service life.

[0039] To further alleviate the clogging of the first permeable reactive wall, in one embodiment, the first permeable reactive wall 102 is also filled with clinoptilolite.

[0040] The clinoptilolite can be used to support and disperse iron-based materials.

[0041] It is understandable that by adopting the above-mentioned solution, filling the first permeable reactive wall 102 with clinoptilolite to support and disperse the iron-based material can reduce the agglomeration of the iron-based material, thereby further alleviating the blockage of the first permeable reactive wall 102. In addition, clinoptilolite also has an adsorption effect, which can further adsorb and fix heavy metals in groundwater.

[0042] In the above embodiments, in order to enable the first permeable reactive wall 102 to have both a good groundwater purification effect and a long service life, the mass ratio of iron-based material and clinoptilolite filled in the first permeable reactive wall 102 can be (1:1) to (3:1).

[0043] Furthermore, to further improve the purification effect of the first permeable reactive barrier 102 on groundwater, the particle size of both the iron-based material and the clinoptilolite can be set to ≤3mm. In practical applications, the particle size of the iron-based material and the clinoptilolite can be adjusted according to the groundwater flow rate. Specifically, the particle size can be set to allow groundwater with a target flow rate to remain in the first permeable reactive barrier 102 for a preset time. The target flow rate can be the actual flow rate of the groundwater flowing towards the first permeable reactive barrier 102, and the preset time can be the time required for the iron-based material and clinoptilolite in the first permeable reactive barrier 102 to sufficiently remove heavy metals and organic matter.

[0044] As mentioned in the above embodiments, the specific structure and location of the nitrate removal unit can be configured according to the location of the target contaminated area and the specific method used to remove nitrates from the target contaminated area. The following will provide a specific method for removing nitrates from target contaminated area A, and a corresponding specific nitrate removal unit:

[0045] In one embodiment, the target contaminated area A includes in-situ nitrate-reducing bacteria, and the nitrate removal unit includes a first delivery unit for delivering a nutrient solution to the target contaminated area A to promote the growth and reproduction of the in-situ nitrate-reducing bacteria.

[0046] The in-situ nitrate-reducing bacteria can be understood as nitrate-reducing bacteria that originally exist in the water body of the target contaminated area, or they can be called indigenous nitrate-reducing bacteria. For example, a large number of nitrate-reducing bacteria are usually present in the groundwater environment of mining, smelting and other engineering projects.

[0047] The nitrate-reducing bacteria can be used to denitrify nitrates in target contaminated areas. Specifically, the nitrate-reducing bacteria can use nitrates as electron acceptors to gradually reduce nitrogen in nitrates to nitrogen gas. The reduction process is as follows:

[0048] NO3 — →NO2 — →NO→N2O→N2

[0049] The nitrate-reducing bacteria may include Pseudomonas, and the Pseudomonas may include Rhodopseudomonas globulus, Rhodopseudomonas erythrosporum, etc.

[0050] The nutrient solution delivered by the first delivery unit to the target contaminated area A may contain, but is not limited to, NaCl, MgCl·6H2O, CaCl2·2H2O, KCl, KH2PO4, NH4Cl, and NaAC. When the nutrient solution includes the above components, to make the nutrient solution more conducive to the growth and reproduction of in-situ nitrate-reducing bacteria, the concentrations of each component may be: 2.5 g / L-5.0 g / L NaCl, 0.1 g / L-0.2 g / L MgCl·6H2O, 0.51 g / L-1 g / L CaCl2·2H2O, 1.5 g / L-3.0 g / L KCl, 0.5 g / L-1.0 g / L KH2PO4, 1.0 g / L-1.5 g / L NH4Cl, and 1.0 g / L-2.0 g / L NaAC. In practical applications, in-situ nitrate-reducing bacteria can be extracted from the target contaminated area A, cultured to obtain external environmental conditions conducive to their growth and reproduction, and then the environment of the target contaminated area A can be controlled to match the external environmental conditions.

[0051] When culturing in-situ nitrate-reducing bacteria in target contaminated area A, the first delivery unit can deliver nutrient solution to target contaminated area A at a rate of 1 hour / day (one hour of delivery per day). Additionally, to ensure the successful growth and reproduction of in-situ nitrate-reducing bacteria in target contaminated area A, N2 can be introduced for 30 minutes before each nutrient solution injection to remove dissolved oxygen in target contaminated area A and create an anaerobic environment conducive to denitrification by nitrate-reducing bacteria.

[0052] It is understandable that by delivering the nutrient solution to the target contaminated area A through the first delivery unit, the in-situ nitrate-reducing bacteria in the target contaminated area A can grow and multiply in large quantities, thereby removing more nitrates from the target contaminated area A and further reducing the nitrates in the groundwater flowing into the first permeable reactive barrier 102. Furthermore, this embodiment of the application uses the method of cultivating in-situ nitrate-reducing bacteria in the target contaminated area A, which is simpler to operate and has lower investment costs compared to introducing exogenous nitrate-reducing bacteria.

[0053] Therefore, the first delivery unit adapted to the above-mentioned removal of nitrates by in-situ nitrate-reducing bacteria in target contaminated area A, such as... Figure 1 As shown, specifically, it may include a nutrient solution storage tank 1011, a first main conveying pipeline 1012, and multiple first branch conveying pipelines 1013. The nutrient solution storage tank 1011 may be located above the ground. The inlet of the first main conveying pipeline 1012 is connected to the outlet of the nutrient solution storage tank 1011. The multiple first branch conveying pipelines 1013 are evenly arranged on the first main conveying pipeline 1012 along the liquid flow direction in the first main conveying pipeline 1012. Figure 1 Multiple circles can represent the influence range of the nutrient solution. A first flow meter 1014 can also be installed on the first main delivery pipeline 1012 to control the flow rate of the delivered nutrient solution.

[0054] When the groundwater treatment system 10 treats groundwater, the first delivery unit may further include a first injection well (not shown in the figure) connecting the surface and the groundwater. There may be multiple first injection wells. The first injection well can be used to receive the nutrient solution flowing out of the first delivery branch pipe 1013 and deliver the nutrient solution to the target contaminated area A in the groundwater.

[0055] It should be understood that the method of removing nitrates from the target contaminated area A by in-situ nitrate-reducing bacteria in the above embodiments is only one specific example. In practical applications, exogenous nitrate-reducing bacteria can also be introduced to remove nitrates from the target contaminated area A. Accordingly, the nitrate removal unit can be a permeable reactive barrier filled with nitrate-reducing bacteria and set in the target contaminated area A.

[0056] Groundwater pollution is often highly complex and frequently contains iodides. Iodine has high mobility and bioaccumulation in the environment, causing persistent damage to the ecological environment and human health. Therefore, in one implementation method, such as Figure 2 As shown, the groundwater treatment system 10 provided in this application embodiment further includes an iodate removal unit, which is used to remove iodate from the target in-situ reaction zone B, which is located between the target contaminated zone A and the first permeable reactive wall 102.

[0057] In this context, the target in-situ reaction region B can be understood as the region where iodate is removed.

[0058] The iodate in the target in-situ reaction zone B may include iodate that is already present in the zone, as well as iodate that flows into the zone from the upstream target contaminated zone A and other zones.

[0059] Accordingly, the target in-situ reaction zone B is set between the target contaminated area and the first permeable reactive wall 102. Specifically, it can be set at a target location between the target contaminated area A and the first permeable reactive wall 102. This target location is a location through which groundwater from the upstream target contaminated area A and other areas can flow.

[0060] The iodate removal unit can be used to remove iodate from the target in-situ reaction region B. The iodate removal unit can remove iodate from the target in-situ reaction region B using chemical, biological, or other methods. In specific implementations, the specific structure and location of the iodate removal unit can be configured according to the location of the target in-situ reaction region B and the specific method used to remove iodate from the target in-situ reaction region B.

[0061] It is understandable that by adopting the above scheme, by setting up the target in-situ reaction zone B between the target contaminated zone B and the first permeable reactive wall 102 and setting up the iodate removal unit, iodides in the groundwater can be further removed, thereby further improving the purification effect of the groundwater.

[0062] As mentioned in the above embodiments, the specific structure and location of the iodate removal unit can be configured according to the location of the target in-situ reaction region B and the specific method used to remove iodate from the target in-situ reaction region B. The following will provide a specific method for removing iodate from the target in-situ reaction region B, and a corresponding specific iodate removal unit:

[0063] In one embodiment, the nutrient solution includes a calcium salt solution, and the iodate removal unit includes a second delivery unit; the second delivery unit is used to deliver a carbonate solution to the target in-situ reaction region B.

[0064] The nutrient solution includes a calcium salt solution, which means that when the nutrient solution is delivered to the target contaminated area A through the first delivery unit, a nutrient solution containing calcium salts can be delivered. Furthermore, the calcium salts are in excess and cannot be completely utilized by the in-situ nitrate-reducing bacteria, resulting in some calcium salts flowing from the target contaminated area A to the target in-situ reaction area B.

[0065] After the calcium salt flows from the target contaminated area A to the target in-situ reaction area B, the target in-situ reaction area B also includes a carbonate solution transported by the second transport unit. Furthermore, in the target in-situ reaction area B, the calcium salt reacts with the carbonate to form calcium carbonate precipitate, and IO3- in the iodate... — It is fixed or adsorbed in calcium carbonate precipitate in the form of co-precipitation, thereby removing iodide and improving the purification effect on groundwater.

[0066] In practice, to ensure the smooth reaction between calcium salts and carbonates, the calcium salt can be a soluble calcium salt, such as CaCl2 or C. 12 H 22 O 14 Ca, etc.; carbonates can be K2CO3, Na2CO3, etc.

[0067] Therefore, a second delivery unit adapted to the above-mentioned removal of iodate from the target in-situ reaction region B, such as... Figure 2 As shown, specifically, it may include a carbonate storage tank 1031, a second main conveying pipeline 1032, and multiple second branch conveying pipelines 1033. The carbonate storage tank 1031 may be installed above the ground surface. The inlet of the second main conveying pipeline 1032 is connected to the outlet of the carbonate storage tank 1031. The multiple branch conveying pipelines 1033 are evenly arranged on the second main conveying pipeline 1032 along the liquid flow direction in the second main conveying pipeline 1032. Figure 2 Multiple circles can represent the influence range of the nutrient solution. A second flow meter 1034 can also be further installed on the second main delivery pipeline 1032 for controlling the flow rate of the delivered carbonate solution.

[0068] When the groundwater treatment system 10 treats groundwater, the second delivery unit may further include a second injection well (not shown in the figure) connecting the surface and the groundwater. There may be multiple second injection wells. The second injection wells can be used to receive the carbonate solution flowing out of the second delivery main pipeline 1032 and deliver the carbonate solution to the target in-situ reaction zone B in the groundwater.

[0069] It should be understood that the method described in the above embodiment, which involves adding calcium salt to the nutrient solution and delivering a carbonate solution to the target in-situ reaction zone B via the second delivery unit, thereby causing iodate and calcium carbonate to co-precipitate and remove iodide from the target in-situ reaction zone B, is merely a specific example. In practical applications, the iodate removal unit can also be a permeable reaction wall located in the target in-situ reaction zone B and filled with a reaction medium capable of removing iodide.

[0070] In practical applications, to prevent sediments and silt in the groundwater flowing towards the first permeable reactive barrier 102 from clogging it, in one embodiment, the groundwater treatment system 10 provided in this application further includes a water filtration unit 104, such as... Figure 3 As shown, the water filtration unit 104 is disposed between the target in-situ reaction zone B and the first permeable reaction wall 102.

[0071] The filtration unit 104 can be used to filter sediments, silt, etc., from the groundwater flowing towards the first permeable reactive barrier 102. Specifically, the sediments can be those obtained in the target in-situ reaction zone B. Since groundwater often coexists with soil in the groundwater layer, the groundwater flowing towards the first permeable reactive barrier 102 may carry some silt to the barrier.

[0072] In this embodiment, the water filtration unit 104 may specifically be a permeable wall filled with quartz sand.

[0073] It is understandable that by adopting the above scheme, by setting up a water filtration unit between the target in-situ reaction zone B and the first permeable reactive wall 102, sediments, silt, and other substances in the groundwater flowing to the first permeable reactive wall 102 can be filtered, thereby preventing the first permeable reactive wall 102 from becoming clogged.

[0074] To further improve the treatment effect on groundwater, in one embodiment, the groundwater treatment system 10 provided in this application further includes a second permeable reactive barrier 105, such as... Figure 4 As shown, the second permeable reactive wall 105 is disposed downstream of the first permeable reactive wall 102, and the second permeable reactive wall 105 is filled with carbon-based adsorbent material.

[0075] The second permeable reactive wall 105 is filled with carbon-based adsorbent material, which can be used to adsorb and remove pollutants such as fluoride, cyanide, iodide, and heavy metals remaining in the groundwater flowing from the first permeable reactive wall 102 to the second permeable reactive wall 105.

[0076] The carbon-based adsorbent material can be coal-based activated carbon, coconut shell activated carbon, etc.

[0077] In practical implementation, to further improve the treatment effect of the second permeable reactive wall 105 on residual iodide in groundwater, the carbon-based adsorbent material may include Ag-based adsorbents. + Modified carbon-based materials, through Ag + It reacts with iodine to form a precipitate, thereby further removing residual iodides from groundwater.

[0078] It is understandable that by adopting the above scheme, by setting a second permeable reactive wall 105 filled with carbon-based adsorbent material downstream of the first permeable reactive wall 102, various pollutants remaining in the groundwater can be further removed, thereby further improving the purification effect of the groundwater.

[0079] In this embodiment of the application, when the groundwater treatment system treats groundwater, the construction process of each reactive wall in the above embodiments, including a first permeable reactive wall, a second permeable reactive wall, and a permeable wall filled with quartz sand (i.e., a filter unit), can be as follows:

[0080] Mechanical grab buckets were used to excavate the foundation trench down to the groundwater-proof bottom slab. Gravity filling was used to sequentially place the filling materials corresponding to each reaction wall, with the filling depth matching the groundwater level.

[0081] For example, after the foundation trench is excavated to the groundwater-proof bottom plate, the filling material corresponding to the filter unit, the filling material corresponding to the first permeable reactive wall, and the filling material corresponding to the second permeable reactive wall are laid down in sequence according to the groundwater flow direction to form the corresponding walls.

[0082] In one embodiment, the groundwater treatment system 10 provided in this application further includes a water-proof unit 106, such as... Figure 4 The water-proof unit 106 shown is disposed on top of the first permeable reactive wall 102 and the second permeable reactive wall 105.

[0083] The water-proof unit 106 can be used to prevent rainwater, surface water and other water from migrating and seeping into the first permeable reactive wall 102 and the second permeable reactive wall 105, thereby preventing impurities contained in rainwater and surface water from affecting the filling material and reaction in the first permeable reactive wall 102 and the second permeable reactive wall 105.

[0084] The water-proof unit 106 may include a barrier hardening layer 1061 and a fill layer 1062 arranged from top to bottom. In specific implementations, to further improve the barrier effect, the barrier hardening layer 1061 may be a C25 concrete surface layer with a thickness of 200mm; the fill layer 1062 may have a compaction degree >95% and a permeability coefficient <10. -7Clay.

[0085] It is understood that by adopting the above scheme, by setting a water-proof unit 106 on the top of the first permeable reactive wall 102 and the second permeable reactive wall 105, rainwater, surface water and other water can be prevented from migrating and seeping into the first permeable reactive wall 102 and the second permeable reactive wall 105, thereby ensuring the treatment effect of the first permeable reactive wall 102 and the second permeable reactive wall 105 on groundwater.

[0086] In one specific embodiment, the groundwater treatment system treats groundwater and includes a first delivery unit, a second delivery unit, a filtration unit 104, a first permeable reactive barrier 102, and a second permeable reactive barrier 105. The first delivery unit delivers a nutrient solution to target contaminated area A to promote the growth and reproduction of nitrate-reducing bacteria in the area; the second delivery unit delivers a carbonate solution to target in-situ reaction area B. The target contaminated area A, the target in-situ reaction area B, the filtration unit 104, the first permeable reactive barrier 102, and the second permeable reactive barrier 105 are arranged sequentially according to the groundwater flow direction.

[0087] Tests revealed the following concentrations of pollutants in the groundwater of a certain mining and smelting project: manganese 45.8 mg / L, copper 3.04 mg / L, zinc 14.8 mg / L, arsenic 87 μg / L, cadmium 11.4 μg / L, lead 220 μg / L, fluoride 4.3 mg / L, cyanide 0.148 mg / L, iodide 31.8 mg / L, and nitrate 1090 mg / L.

[0088] After the groundwater is treated using the groundwater treatment system 10 provided in the above embodiments of this application, the concentrations of various pollutants in the groundwater are as follows: manganese 3 mg / L, copper 1.5 mg / L, zinc 5 mg / L, arsenic 50 μg / L, cadmium 10 μg / L, lead 100 μg / L, fluoride 2 mg / L, cyanide 0.1 mg / L, iodide 1.0 mg / L, and nitrate 100 mg / L.

[0089] Therefore, the groundwater treatment system provided in this application embodiment can remove most of the pollutants such as heavy metals, fluorides, cyanides, and iodides from groundwater, and has a good purification effect.

[0090] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0091] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A groundwater treatment system, characterized in that, The system includes a nitrate removal unit, an iodate removal unit, and a first permeable reactive barrier. The nitrate removal unit removes nitrates from a target contaminated area and includes a first delivery unit for delivering a nutrient solution, which includes a calcium salt solution, to the target contaminated area. The iodate removal unit removes iodates from a target in-situ reaction area and includes a second delivery unit for delivering a carbonate solution to the target in-situ reaction area. The first permeable reactive barrier is located downstream of the target contaminated area and is filled with an iron-based material. The target in-situ reaction area is located between the target contaminated area and the first permeable reactive barrier.

2. The groundwater treatment system according to claim 1, characterized in that, The target contaminated area includes in-situ nitrate-reducing bacteria, and the nutrient solution delivered by the first delivery unit is also used to promote the growth and reproduction of the in-situ nitrate-reducing bacteria.

3. The groundwater treatment system according to claim 1, characterized in that, The first delivery unit includes a first injection well connecting the surface water and the groundwater, and the second delivery unit includes a second injection well connecting the surface water and the groundwater.

4. The groundwater treatment system according to claim 1, characterized in that, The system also includes a water filtration unit disposed between the target in-situ reaction zone and the first permeable reaction wall.

5. The groundwater treatment system according to claim 1, characterized in that, The system also includes a second permeable reactive wall, which is located downstream of the first permeable reactive wall and is filled with a carbon-based adsorbent material.

6. The groundwater treatment system according to claim 5, characterized in that, The carbon-based adsorbent material includes Ag-based adsorbents. + Modified carbon-based materials.

7. The groundwater treatment system according to claim 5, characterized in that, The system also includes a water-proof unit, which is disposed on top of the first permeable reactive wall and the second permeable reactive wall.

8. The groundwater treatment system according to claim 1, characterized in that, The first permeable reactive wall is also filled with clinoptilolite.

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