An assembly of adjustable permeable reactive wall structure and a method for treating a plume of pollution

Abstract

The application discloses an assembly-adjustable permeable reaction wall structure and a method for treating a pollution plume. The permeable reaction wall structure comprises a plurality of filler box assemblies arranged side by side, a slide rail arranged below the filler box assemblies, and two symmetrically arranged blocking slide plates arranged on the slide rail and used for selectively blocking the filler box assemblies. The method comprises the following steps: S1, determining the size of the permeable reaction wall; and S2, replacing the active filler. The application aims to effectively overcome the problems of insufficient impact load resistance of a conventional PRB and difficulty in replacing the filler. In the structural design, the parallel double-gate structure, the upper and lower integral series filler box and the adjustable active filler thickness structure design idea are adopted to enhance the response capability of the PRB to the pollution load fluctuation. In the filler design, the modular design idea of the partition replacement and the standardized filler box is adopted to realize the rapid replacement and response of the PRB filler and ensure that the target pollutants are completely blocked or intercepted in the PRB.

Description

Technical Field

[0001] This invention relates to the field of groundwater monitoring and treatment technology, specifically to an assembled adjustable permeable reactive barrier structure and a method for treating pollution plumes. Background Technology

[0002] Permeable reactive barriers (PRBs) are a common in-situ remediation technology for underground systems. They involve constructing permeable treatment units containing specific active fillers along the path of contaminated groundwater. Under the influence of natural hydraulic gradients, PRBs intercept or remove contaminants through adsorption, sedimentation, oxidation-reduction, or biochemical reactions. PRB technology offers advantages such as simple construction, no need for external power units or surface treatment systems, and long service life. However, as the PRB operates underground, reaction products gradually deposit within the wall, leading to a decrease in porosity and permeability, thus weakening the PRB's hydraulic interception capacity and increasing the risk of contaminant plumes flowing around it. Simultaneously, the consumption of active fillers and the reduction in reaction surface area due to mineral precipitation also decrease the long-term reactivity of the PRB. Therefore, PRBs require replacement or cleaning of the filler material after a period of use. Currently, the replacement or cleaning of the filler in PRBs involves first excavating the old filler buried underground using excavation equipment, then directly filling it with new filler, or cleaning and purifying the old filler before refilling. However, since PRB filler is mostly loose granular and interacts with the surrounding soil, traditional excavation and replacement methods suffer from problems such as difficulty in replacing partially failed filler, high construction difficulty, easy secondary pollution and sidewall soil collapse, and high cost. In addition, since PRB is mostly a fixed structure with fixed size and filler volume, its treatment capacity is limited, and its response to fluctuations in pollution load (influent water quality and quantity) is weak.

[0003] In summary, the core problems of existing PRB technology include: (1) Fixed structure has great limitations: Traditional PRB is mostly designed as a fixed structure, which cannot flexibly adjust the treatment capacity according to changes in water quality and quantity (such as when the flow difference between the dry season and the rainy season is large, the PRB treatment efficiency fluctuates significantly); (2) It is difficult to replace the packing material: Replacing the packing material requires stopping the machine or disassembling the structure, which leads to the interruption of repair and affects the continuity of groundwater repair. For example, utility model patent CN216377762U discloses a device for remediating organically polluted groundwater using PRB technology. The device includes a pH adjustment tank, a chemical oxidation tank, and a storage tank arranged sequentially, connected by pipelines. A circulation pump is installed on the pipelines. An injection well, a PRB filling wall, and a pumping well are arranged sequentially along the flow direction of the organically polluted groundwater. A clean water pump is installed inside the pumping well, and the outlet of the submersible pump is connected to a pumping pipe. The upper end of the pumping pipe is connected to the pH adjustment tank, and the upper part of the storage tank is connected to the injection well via an injection pipe. This utility model effectively solves the problem of low remediation efficiency of organically polluted groundwater by combining upstream in-situ injection oxidation, PRB reaction system adsorption and degradation, and downstream monitoring and extraction treatment. However, this device still suffers from the problem of inconvenient PRB packing material replacement. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an assembled adjustable permeable reactive barrier structure and a method for treating pollution plumes.

[0005] The technical solution of this invention is:

[0006] An adjustable permeable reactive wall structure includes several packing box assemblies arranged side by side, a slide rail located below the packing box assemblies, and two symmetrically arranged sealing slide plates slidably disposed on the slide rail for selectively sealing the packing box assemblies.

[0007] The packing box assembly includes several PRB packing boxes arranged from bottom to top and fixedly connected to each other. Each PRB packing box has a screen at its front and rear openings. The PRB packing box contains active packing. A slot is provided at one of the screens located at the front end of the PRB packing box.

[0008] The sealing slide plate has several insert plates arranged from bottom to top on its rear side. Each insert plate is slidably and detachably connected to each slot located on the same horizontal plane, so that the corresponding PRB packing box remains closed after connection.

[0009] The stuffing box assembly and the slide rail are provided with concrete slabs on both sides and at the bottom for fixing the stuffing box assembly and the slide rail.

[0010] Furthermore, the packing box assembly includes 4 to 12 groups, and each group of the packing box assembly includes 6 to 20 PRB packing boxes. The PRB packing boxes are provided with several porous partitions at equal intervals inside for filling with active filler, which is one or more of zero-valent iron, activated carbon and zeolite.

[0011] Note: By dividing the PRB into multiple modules, each module can be filled and replaced independently, reducing the amount of construction work and lowering costs.

[0012] Furthermore, the two sealing slide plates are driven to slide by two drive motors, which are located inside the stratum above the ground or groundwater level. The output end of the drive motor is provided with a first rotating shaft, on which a first transmission steel chain is meshed. The lower end of the first transmission steel chain is meshed with a second rotating shaft, the rear end of which is rotatably connected to the front sidewall of the concrete slab. The front end of the second rotating shaft is meshed with a second transmission steel chain, which extends horizontally toward the middle of the packing box assembly. The end of the second transmission steel chain is meshed with a third rotating shaft, the rear end of which is rotatably connected to the front sidewall of the concrete slab. The third rotating shaft is located below the slide rail. Several T-shaped blocks are fixedly provided on the second transmission steel chain, and the upper rear side of the T-shaped blocks is fixedly connected to the lower part of the front sidewall of the sealing slide plate.

[0013] Description: A permeable reactive wall with an adjustable permeable area is formed by selectively sealing the packing box assembly using a sealing slide.

[0014] Furthermore, there are 2 to 3 T-shaped blocks, and an L-shaped block is fixed in the middle of the first transmission steel chain. A slot is provided at the upper edge of the sealing slide plate. When the sealing slide plate slides to both sides, the L-shaped block descends synchronously and engages with the slot.

[0015] Explanation: The L-shaped locking blocks are used to assist in positioning the blocking sliding plate when it moves to the sides.

[0016] Furthermore, the slide rail includes a first slide groove for sliding the sealing slide plate and a second slide groove for sliding the packing box assembly. A set of rollers is provided on each of the front and rear sides of the bottom of the lowest PRB packing box. A limiting groove is provided in the middle of the bottom of the PRB packing box between the two sets of rollers. One side of the limiting groove is an arc-shaped recess. Two bow-shaped blocks are symmetrically arranged in the receiving cavity inside the second slide groove. One end of the bow-shaped block passes through the first slot above the second slide groove and is located below the two middle sets of packing box assemblies. The other end of the bow-shaped block passes through the second slot above the second slide groove and is located below the packing box assemblies on both sides. The bottom of the bow-shaped block is fixedly connected to the bottom of the receiving cavity by several springs. The inner sides of the two protrusions of the bow-shaped block are provided with arc-shaped recesses for engaging with the limiting groove.

[0017] Note: The bow-shaped locking block allows the stuffing box assembly to slide automatically inward, facilitating replacement and retrieval.

[0018] Furthermore, a hook is provided on the top of the PRB packing box located at the top, and a water quality sensor is provided on the front side wall of the sealing slide plate.

[0019] Note: The hook design facilitates the removal of the entire packing box assembly, and the water quality sensor enables real-time monitoring of groundwater quality, allowing for appropriate adjustments.

[0020] The present invention also provides a method for treating pollution plumes by assembling an adjustable permeable reactive barrier structure, comprising the following steps:

[0021] S1. Determining the Dimensions of the Permeable Reactive Wall: All packing box assemblies together form the permeable reactive wall. By adjusting the sealing positions of the two sealing plates, the permeable length, permeable width, and permeable height of the permeable reactive wall can be adjusted according to the actual environmental conditions. The calculation formula is as follows:

[0022] T PRB =u·t R ·SF

[0023]

[0024] In the formula, T PRB The permeable thickness of the permeable reactive barrier, in meters (m); L PRB H represents the permeable length of the permeable reactive barrier, in meters (m). PRB The permeable height of the permeable reactive barrier is in meters (m); u is the actual flow velocity of groundwater through the permeable reactive barrier, in meters per second (m·d). -1 ;t R The residence time required for pollutants to decrease to the target concentration level is expressed in days (d); C0 is the influent concentration of the permeable reactive barrier, expressed in mg·L⁻¹. -1C s The target effluent concentration for the permeable reactive barrier is expressed in mg·L⁻¹. -1 k is the first-order reaction rate constant, in h⁻¹. -1 SF is the safety factor, taken as 3-5; Q is the groundwater flow rate through the permeable reactive barrier, in cubic meters per second (m³). 3 ·d -1 ;t L The theoretical service life of the PRB stuffing box is expressed in days (d); q max The maximum adsorption capacity of a unit PRB activated packing for pollutants is expressed in g·g. -1 ρ represents the dry density of the PRB activated filler, in g·L. -1 θ represents the porosity of the PRB active filler.

[0025] S2. Replacement of active packing: When it is necessary to replace the active packing inside the PRB packing box, remove the two packing box assemblies in the middle as a whole, and at the same time, slide the packing box assemblies on both sides inward to fill the position of the removed packing box assemblies. Then, insert the entire set of packing box assemblies, consisting of PRB packing boxes filled with new active packing, from both sides of the permeable reactive wall. Repeat this process to complete the replacement of all the packing box assemblies that need to be replaced.

[0026] Furthermore, the theoretical service life t of the PRB stuffing box in S1 L It is 1825d.

[0027] Furthermore, in S1, the permeability coefficient of the active filler is 2 to 10 times that of the permeability coefficient of the water-containing medium surrounding the permeable reaction wall, and the pore size of the screen is 1 / 3 to 1 / 2 of the pore size of the active filler.

[0028] Explanation: By optimizing the ratio between the permeability coefficient of the active filler and the permeability coefficient of the water-containing medium surrounding the permeable reactive wall, the optimal particle size of the active filler with the best permeability efficiency can be determined.

[0029] The beneficial effects of this invention are:

[0030] (1) The present invention provides an adjustable permeable reactive wall structure to effectively overcome the problems of insufficient shock load resistance and difficult replacement of packing in traditional PRB. In terms of structural design, it adopts the design concept of double gate parallel connection, upper and lower integrated series packing boxes and adjustable active packing thickness to ensure that the target pollutants are completely blocked or intercepted in the PRB. In terms of packing design, it adopts the modular design concept of zone replacement and standardized packing boxes to realize the rapid replacement and response of PRB packing.

[0031] (2) The assembled adjustable permeable reactive wall structure of the present invention can flexibly adjust the packing volume and treatment capacity according to the pollution load, and flexibly adjust the packing volume and pollutant treatment capacity of the PRB to adapt to changes in influent volume and water quality; and can set up multiple reaction zones according to different packings to perform graded treatment for different pollutants, and combine multiple pollutant treatment technologies (physical, chemical or biological, etc.) to improve treatment efficiency.

[0032] (3) The assembled adjustable permeable reactive barrier structure of the present invention divides the PRB into multiple modules, each of which can be filled and replaced independently, reducing the amount of construction and lowering costs; it adopts standardized packing boxes, which are convenient for on-site assembly and replacement. According to specific groundwater remediation scenarios, target pollutants and pollution loads, the matching packing boxes are customized, including packing type, particle size distribution, etc., to ensure that its reactivity and permeability can meet the remediation requirements. The packing plastic boxes follow productization, modularization and standardization development, and are mass-produced in the factory. Each packing box is transported to the site for rapid assembly, plug and play, and has good scalability, sustainability and resistance stability; in addition, when the reactive material loses its activity due to adsorption saturation and the purification efficiency decreases, the packing box filled with reactive material can be removed for material recycling and reuse and new reactive material can be replaced, and the packing can be replaced while maintaining its treatment capacity.

[0033] (4) The method for treating pollution plumes using an adjustable permeable reactive barrier structure according to the present invention can achieve...

[0034] Intelligent monitoring and real-time feedback: The system monitors parameters such as influent concentration, effluent concentration, flow velocity, and flux of the PRB in real time through sensors. Based on the monitoring data, when the PRB is punctured (i.e., the packing fails), it prompts the user to adjust the PRB structure or replace the packing. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of an adjustable and permeable reactive wall structure according to the present invention.

[0036] Figure 2 This is a front view of an assembled adjustable permeable reactive wall structure according to the present invention;

[0037] Figure 3 This is a schematic diagram of the internal structure of a PRB packing box for an adjustable and permeable reactive wall structure according to the present invention.

[0038] Figure 4 This is a side view of the lowest PRB packing box in an assembled adjustable permeable reactive wall structure according to the present invention;

[0039] Figure 5 This is a top view of an assembled adjustable permeable reactive wall structure according to the present invention;

[0040] Figure 6 This is a schematic diagram of the internal structure of the slide rail of an adjustable and permeable reactive wall structure according to the present invention;

[0041] Figure 7 This is a schematic diagram of the connection structure between the slide rail and the PRB packing box of an adjustable and permeable reactive wall structure according to the present invention.

[0042] Figure 8 This is an enlarged structural diagram of the connection between the slide rail and the PRB packing box of an adjustable and permeable reactive wall structure according to the present invention.

[0043] Figure 9 This is a top view of a sealing slide plate of an adjustable and permeable reactive wall structure according to the present invention;

[0044] Figure 10 This is a side view of an assembled adjustable permeable reactive wall structure according to the present invention.

[0045] Among them, 1-stuffing box assembly, 11-PRB stuffing box, 12-screen, 13-slot, 14-roller, 15-limiting groove, 16-hook, 17-perforated partition, 2-slide rail, 21-first slide groove, 22-second slide groove, 23-cavity, 24-first slot, 25-second slot, 26-spring, 3-sealing slide plate, 31-insertion plate, 32-slot, 4-concrete slab, 5-drive motor, 51-first rotating shaft, 52-second rotating shaft, 53-third rotating shaft, 6-first transmission steel chain, 61-L-shaped locking block, 7-second transmission steel chain, 71-T-shaped locking block, 8-bow-shaped locking block, 9-water quality detector. Detailed Implementation

[0046] Example 1

[0047] like Figure 1 As shown, an adjustable permeable reactive wall structure includes eight sets of packing box assemblies 1 arranged side by side, a slide rail 2 located below the packing box assembly 1, and two symmetrically arranged sealing slide plates 3 slidably arranged on the slide rail 2 for selectively sealing the packing box assembly 1.

[0048] like Figure 2 and Figure 3As shown, the packing box assembly 1 includes eight PRB packing boxes 11 arranged from bottom to top and fixedly connected to each other. Each PRB packing box 11 has a screen 12 at the opening on both the front and rear sides. The PRB packing box 11 contains activated packing. The PRB packing box 11 has several porous partitions 17 evenly spaced inside for filling with activated packing. The activated packing is a mixture of activated carbon and zeolite in a 1:1 mass ratio. The front end of the PRB packing box 11 extends out to a screen 12 located in front and has a slot 13. The top of the uppermost PRB packing box 11 has a hook 16. A water quality sensor 9 is provided on the front side wall of the sealing slide plate 3.

[0049] The PRB packing box 11 adopts an ISO standard snap-fit ​​(DIN46267 type) interface design, supports horizontal / vertical expansion, and the box body material is UV-resistant modified PP (tensile strength ≥30MPa); the screen 12 has an anti-clogging design: the front / rear walls use double-layer stainless steel screens (SS304), fixed by laser welding process, which can intercept suspended solids; rapid assembly technology: the box body is connected on-site by a hydraulic assembly machine, and the top cover of the box body adopts a magnetic locking and hinge opening and closing structure, which supports single-person operation; the water quality sensor 9 is a commercially available water quality sensor;

[0050] like Figure 9 and Figure 10 As shown, a concrete plate 4 for fixing the stuffing box assembly 1 and the slide rail 2 is provided on both sides and the bottom. After the sealing slide plate 3 is closed, several insert plates 31 are provided on the side from bottom to top. Each insert plate 31 is slidably and detachably connected to each slot 13 located on the same horizontal plane. After the connection, the corresponding PRB stuffing box 11 is kept closed.

[0051] like Figure 1 , Figure 2 and Figure 5As shown, the two sealing slide plates 3 are driven to slide by two drive motors 5. The drive motors 5 are located inside the stratum above the ground or groundwater level. The output end of the drive motor 5 is provided with a first rotating shaft 51, on which a first transmission steel chain 6 is meshed. The lower end of the first transmission steel chain 6 is meshed with a second rotating shaft 52. The rear end of the second rotating shaft 52 is rotatably connected to the front side wall of the concrete slab 4, and the front end of the second rotating shaft 52 is meshed with a second transmission steel chain 7. The second transmission steel chain 7 extends horizontally towards the middle of the packing box assembly 1, and the second transmission steel chain 7... The end of the chain 7 is meshed with a third rotating shaft 53. The rear end of the third rotating shaft 53 is rotatably connected to the front side wall of the concrete slab 4. The third rotating shaft 53 is located below the slide rail 2. Two T-shaped blocks 71 are fixedly installed on the second transmission steel chain 7. The upper rear side of the T-shaped blocks 71 is fixedly connected to the lower part of the front side wall of the sealing slide plate 3. An L-shaped block 61 is fixedly installed in the middle of the first transmission steel chain 6. A slot 32 is provided at the upper edge of the sealing slide plate 3. When the sealing slide plate 3 slides to both sides, the L-shaped block 61 descends synchronously and engages with the slot 32. The drive motor 5 is a commercially available high-power motor.

[0052] like Figures 5-8 As shown, the slide rail 2 includes a first slide groove 21 for sliding the sealing slide plate 3 and a second slide groove 22 for sliding the packing box assembly 1. The bottom of the lowest PRB packing box 11 is provided with a set of rollers 14 on both the front and rear sides. The bottom of the PRB packing box 11 between the two sets of rollers 14 is provided with a limiting groove 15 in the middle of the bottom. One side of the limiting groove 15 is an arc-shaped recess. Two bow-shaped blocks 8 are symmetrically provided in the receiving cavity 23 inside the second slide groove 22. One end of the bow-shaped block 8 passes through the first slot 24 and extends above the second slide groove 22, corresponding to the bottom of the two packing box assemblies 1 in the middle. The other end of the bow-shaped block 8 passes through the second slot 25 and extends above the second slide groove 22, corresponding to the bottom of the packing box assemblies 1 on both sides. The bottom of the bow-shaped block 8 is fixedly connected to the bottom of the receiving cavity 23 by several springs 26. The inner side of the two protrusions of the bow-shaped block 8 is provided with an arc-shaped recess for docking with the limiting groove 15.

[0053] Example 2

[0054] The difference between this embodiment and Embodiment 1 is that:

[0055] The stuffing box assembly 1 consists of 4 sets, and the stuffing box assembly 1 includes 6 PRB stuffing boxes 11 that are fixedly connected to each other and arranged from bottom to top.

[0056] Example 3

[0057] The difference between this embodiment and Embodiment 1 is that:

[0058] The stuffing box assembly 1 consists of 12 sets, including 20 PRB stuffing boxes 11 that are fixedly connected to each other and arranged from bottom to top.

[0059] Example 4

[0060] The difference between this embodiment and Embodiment 1 is that:

[0061] Three T-shaped locking blocks 71 are fixedly installed on the second transmission steel chain 7.

[0062] Example 5

[0063] The difference between this embodiment and Embodiment 1 is that:

[0064] The active filler is zero-valent iron.

[0065] Example 6

[0066] This embodiment is a method for treating pollution plumes using an adjustable and permeable reactive barrier structure, as described in Embodiment 1, and includes the following steps:

[0067] S1. Determination of the dimensions of the permeable reactive wall: All packing box assemblies 1 together form the permeable reactive wall. By adjusting the sealing positions of the two sealing plates 3, the permeable length, permeable width, and permeable height of the permeable reactive wall can be adjusted according to the actual environmental conditions. The calculation formula is as follows:

[0068] T PRB =u·t R ·SF

[0069]

[0070] In the formula, T PRB The permeable thickness of the permeable reactive barrier, in meters (m); L PRB H represents the permeable length of the permeable reactive barrier, in meters (m). PRB The permeable height of the permeable reactive barrier is in meters (m); u is the actual flow velocity of groundwater through the permeable reactive barrier, in meters per second (m·d). -1 ;t R The residence time required for pollutants to decrease to the target concentration level is expressed in days (d); C0 is the influent concentration of the permeable reactive barrier, expressed in mg·L⁻¹. -1 C s The target effluent concentration for the permeable reactive barrier is expressed in mg·L⁻¹. -1 k is the first-order reaction rate constant, in h⁻¹. -1 SF is the safety factor, taken as 3-5; Q is the groundwater flow rate through the permeable reactive barrier, in m³·d. -1 ;t L The theoretical service life of PRB stuffing box 11 is expressed in days (d); q max The maximum adsorption capacity of a unit PRB activated packing for pollutants is expressed in g·g. -1 ρ represents the dry density of the PRB activated filler, in g·L.-1 θ represents the porosity of the PRB active filler.

[0071] The permeability coefficient of the active packing is 8 times that of the water-containing medium surrounding the permeable reaction wall, and the pore size of the screen 12 is 1 / 3 of the pore size of the active packing.

[0072] S2. Replacement of active packing: When it is necessary to replace the active packing inside the PRB packing box 11, remove the two packing box assemblies 1 in the middle as a whole, and at the same time, slide the packing box assemblies 1 on both sides inward to fill the position of the removed packing box assemblies 1. Then, insert the entire set of packing box assemblies 11, which are filled with new active packing, from both sides of the permeable reactive wall. Repeat this process to complete the replacement of all the packing box assemblies 1 that need to be replaced.

[0073] Example 7

[0074] The difference between this embodiment and embodiment 6 is that:

[0075] The permeability coefficient of the active packing is twice that of the permeability coefficient of the water-containing medium surrounding the permeable reaction wall, and the pore size of the screen 12 is 1 / 3 of the pore size of the active packing.

[0076] Example 8

[0077] The difference between this embodiment and embodiment 6 is that:

[0078] The permeability coefficient of the active packing is 10 times that of the water-containing medium surrounding the permeable reaction wall, and the pore size of the screen 12 is 1 / 2 the pore size of the active packing.

[0079] Working principle: The working principle of an assembled adjustable permeable reactive wall structure of the present invention will be briefly explained below in conjunction with the method of the present invention.

[0080] When performing S1, the blocking position of the blocking slide plate 3 needs to be adjusted, and the drive motor 5 is turned on to drive the first rotating shaft 51 to rotate. At the same time, under the action of the first transmission steel chain 6 and the second transmission steel chain 7, the second rotating shaft 52 and the third rotating shaft 53 are driven to rotate synchronously, so that the two sets of T-shaped blocks 71 drive the two blocking slide plates 3 to slide inward along the first sliding groove 21. At the same time, each insert plate 31 is inserted into each slot 13 to complete the blocking of the screen 12 and prevent water from flowing through.

[0081] When performing S2, it is necessary to replace the stuffing box assembly 1. The hooks 16 on the two stuffing box assemblies 1 located in the middle are connected by an external steel wire rope. The two stuffing box assemblies 1 are lifted by a winch. At the same time, after the stuffing box assembly 1 is lifted, the bottom limiting grooves 15 of the two stuffing box assemblies 1 located on the outermost sides are gradually pushed out under the combined action of water force and spring 26. When the outer end of the bow-shaped locking block 8 is pushed upward through the second slot 25, the limiting groove 15 is pushed under the action of the arc end face. Together with the water force and buoyancy, the entire stuffing box assembly 1 is pushed, thereby pushing the stuffing box assemblies 1 located on both sides to the middle position.

[0082] Subsequently, the new packing box assembly 1 with replaced active packing is placed into the positions on both sides of the permeable reactive wall by a ground winch. After placement, the bow-shaped locking block 8 is pressed down. At the same time, the top of the bow-shaped locking block 8 located on the inner side is also squeezed by the limiting groove 15 and descends through the second slot 24, thus completing the reset of the bow-shaped locking block 8 and the replacement of the packing box assembly 1.

[0083] Experimental Example

[0084] Taking the scenario of PRB remediation of contaminated groundwater from a municipal solid waste landfill as an example, the target pollutant is ammonia nitrogen, and zeolite is selected as the PRB filler with a density ρ of 1.75 t·m³. -3 The porosity θ is 0.45, and the adsorption rate constant k of the zeolite for ammonia nitrogen is 0.5d. -1 The maximum adsorption capacity of zeolite for ammonia nitrogen is 0.016 (g·g). -1 The highest concentration of ammonia nitrogen in the PRB influent was 97.4 mg·L⁻¹. -1 At 1.5 mg·L -1 To achieve the target concentration of ammonia nitrogen in the effluent (i.e., the Class IV groundwater quality standard), the actual groundwater flow velocity u through the PRB is 0.058 m·d. -1 SF is taken as an empirical value of 4, and T is calculated using the above formula. PRB It is 1.93m.

[0085] Assuming the theoretical operating life of the PRB is 5 years, the groundwater flow through the PRB is 52.8 m³. 3 ·d -1 The aquifer thickness at the installation location is approximately 16m, and according to requirements, the bottom of the PRB should be embedded 0.6m below the weakly permeable layer. Therefore, H PRB The value is 16.6m, and the T calculated above is used as the reference. PRB Substituting into the above formula, the required L can be calculated. PRB The length is 20.8m. The length, width, and height of the stuffing box assembly 1 have now been calculated.

Claims

1. A method for treating pollution plumes using an adjustable permeable reactive barrier structure, characterized in that, The permeable reactive wall includes several packing box assemblies (1) arranged side by side. Each packing box assembly (1) includes 4 to 12 sets of slide rails (2) located below the packing box assembly (1) and two symmetrically arranged sealing slide plates (3) that are slidably arranged on the slide rails (2) and used for selectively sealing the packing box assembly (1). The packing box assembly (1) includes a number of PRB packing boxes (11) arranged from bottom to top and fixedly connected to each other. Each PRB packing box (11) has a screen (12) at the front and rear openings. The PRB packing box (11) is filled with active packing. A slot (13) is provided at the front end of the PRB packing box (11) where one of the screens (12) is located. The sealing slide plate (3) has several insert plates (31) arranged from bottom to top on the rear side. Each insert plate (31) is slidably and detachably connected to each slot (13) located on the same horizontal plane. After connection, the corresponding PRB packing box (11) is kept closed. The stuffing box assembly (1) and the slide rail (2) are provided with concrete plates (4) on both sides and at the bottom for fixing the stuffing box assembly (1) and the slide rail (2). The slide rail (2) includes a first slide groove (21) for sliding the sealing slide plate (3) and a second slide groove (22) for sliding the packing box assembly (1). The bottom of the lowest PRB packing box (11) has a set of rollers (14) on both the front and rear sides. A limiting groove (15) is located in the middle of the bottom of the PRB packing box (11) between the two sets of rollers (14). One side of the limiting groove (15) is an arc-shaped recess. Two bow-shaped locking blocks are symmetrically arranged in the receiving cavity (23) inside the second slide groove (22). 8), one end of the bow-shaped block (8) passes through the first slot (24) and extends above the second slide groove (22) and corresponds to the two sets of the packing box assembly (1) located in the middle. The other end of the bow-shaped block (8) passes through the second slot (25) and extends above the second slide groove (22) and corresponds to the packing box assembly (1) located on both sides. The bottom of the bow-shaped block (8) is fixedly connected to the bottom of the receiving cavity (23) by several springs (26). The inner side of the two protrusions of the bow-shaped block (8) is provided with arc-shaped recesses for docking with the limiting groove (15). The method includes the following steps: S1. Determination of the size of the permeable reactive wall: All packing box components (1) together form a permeable reactive wall. By adjusting the sealing position of the two sealing slide plates (3), the permeable length of the permeable reactive wall can be adjusted according to the actual environmental conditions. S2. Replacement of active packing: When it is necessary to replace the active packing inside the PRB packing box (11), the two packing box assemblies (1) in the middle are taken out as a whole, and the packing box assemblies (1) on both sides slide inward to fill the position of the removed packing box assembly (1). Then, a whole set of packing box assemblies (1) consisting of PRB packing boxes (11) filled with new active packing is placed from both sides of the permeable reactive wall. In this way, all the packing box assemblies (1) that need to be replaced are replaced.

2. The method for treating pollution plumes using an adjustable permeable reactive barrier structure according to claim 1, characterized in that, Each packing box assembly (1) includes 6 to 20 PRB packing boxes (11). The PRB packing box (11) has several porous partitions (17) evenly spaced inside for filling with active filler, which is one or more of zero-valent iron, activated carbon and zeolite.

3. The method for treating pollution plumes using an adjustable permeable reactive barrier structure according to claim 1, characterized in that, The two sealing slide plates (3) are driven to slide by two drive motors (5). The drive motors (5) are located inside the stratum above the ground or groundwater level. The output end of the drive motors (5) is provided with a first rotating shaft (51). A first transmission steel chain (6) is meshed on the first rotating shaft (51). A second rotating shaft (52) is meshed at the lower end of the first transmission steel chain (6). The rear end of the second rotating shaft (52) is rotatably connected to the front side wall of the concrete slab (4). The front end of the second rotating shaft (52) is meshed with the concrete slab (4). A second transmission steel chain (7) is connected, which extends horizontally toward the middle of the stuffing box assembly (1), and the end of the second transmission steel chain (7) is engaged with a third rotating shaft (53). The rear end of the third rotating shaft (53) is rotatably connected to the front side wall of the concrete slab (4). The third rotating shaft (53) is located below the slide rail (2). Several T-shaped blocks (71) are fixedly provided on the second transmission steel chain (7). The upper rear side of the T-shaped blocks (71) is fixedly connected to the lower part of the front side wall of the sealing slide plate (3).

4. The method for treating pollution plumes using an adjustable permeable reactive barrier structure according to claim 3, characterized in that, There are 2 to 3 T-shaped blocks (71), and an L-shaped block (61) is fixed in the middle of the first transmission steel chain (6). A slot (32) is provided at the upper edge of the sealing slide plate (3). When the sealing slide plate (3) slides to both sides, the L-shaped block (61) descends synchronously and docks with the slot (32).

5. A method for treating pollution plumes using an adjustable permeable reactive barrier structure according to claim 1, characterized in that, The top of the PRB packing box (11) located at the top is provided with a hook (16), and a water quality sensor (9) is provided on the front side wall of the sealing slide plate (3).

6. The method for treating pollution plumes using an adjustable permeable reactive barrier structure according to claim 1, characterized in that, In S1, the calculation formula is as follows: ； ； In the formula, T PRB The permeable thickness of the permeable reactive barrier is expressed in meters (m). L PRB The permeable length of the permeable reactive barrier, in meters (m). H PRB The permeability height of the permeable reactive barrier, in meters (m). u The actual flow velocity of groundwater through the permeable reactive barrier is expressed in m·d. -1 ; t R The residence time required for pollutants to decrease to the target concentration level, expressed in days (d). C 0 represents the influent concentration of the permeable reactive barrier, in mg·L⁻¹. -1 ; C s The target effluent concentration for the permeable reactive barrier is expressed in mg·L⁻¹. -1 ; k The first-order reaction rate constant is expressed in h⁻¹. -1 SF is the safety factor, which is 3 to 5. Q : This represents the groundwater flow rate through the permeable reactive barrier, expressed in meters (m³). 3 ·d -1 ; t L The theoretical operating life of the PRB stuffing box (11) is expressed in days. q max The maximum adsorption capacity of a unit PRB activated packing for pollutants is expressed in g·g. -1 ; ρ The dry density of the PRB active filler is given in g·L. -1 ; θ The porosity of the PRB active filler is given.

7. A method for treating pollution plumes using an adjustable permeable reactive barrier structure according to claim 6, characterized in that, The theoretical operating life t of the PRB stuffing box (11) in S1 L It is 1825d.

8. A method for treating pollution plumes using an adjustable permeable reactive barrier structure according to claim 6, characterized in that, The permeability coefficient of the active filler in S1 is 2 to 10 times that of the permeability coefficient of the water-containing medium surrounding the permeable reaction wall, and the pore size of the screen (12) is 1 / 3 to 1 / 2 of the pore size of the active filler.

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