Assembly-adjustable permeable reactive barrier structure and method for treating pollution plume by assembly-adjustable permeable reactive barrier structure

Abstract

The invention discloses an assembly-adjustable permeable reactive barrier structure and a pollution plume treatment method thereof. The permeable reactive barrier structure comprises a plurality of filler box assemblies arranged side by side, a sliding rail located below the filler box assemblies and two symmetrically-arranged plugging sliding plates which are arranged on the sliding rail in a sliding mode and used for selectively plugging the filler box assemblies. The method comprises the following steps: S1, determining the size of the permeable reactive barrier; and S2, replacing the active filler. The invention aims to effectively overcome the problems of insufficient impact load resistance, difficulty in filler replacement and the like of the traditional PRB, and in structural design, the structural design thought of double-gate parallel connection, up-down integral series connection of filler boxes and adjustable active filler thickness is adopted, so that the responsiveness of the PRB to pollution load fluctuation is enhanced; in the aspect of filler design, the modular design thought of partition replacement and standardization of a filler box is adopted, rapid replacement and response of PRB filler are achieved, and it is ensured that target pollutants are completely blocked or intercepted in PRB.

Description

Technical Field

[0001] The present invention relates to the technical field of groundwater monitoring and treatment, in particular to an assembled adjustable permeable reaction wall structure and a method for treating a contaminated plume thereof. Background Art

[0002] Permeable reactive walls (PRBs) are a common in-situ remediation technology for underground water. They construct permeable treatment cells containing specialized active fillers along the contaminated groundwater flow path. Under the influence of natural hydraulic gradients, they intercept or remove pollutants through adsorption, precipitation, redox, or biochemical reactions. PRB technology offers advantages such as simple construction, the absence of external power plants or surface treatment systems, and a long operational life. However, as PRBs operate underground, reaction products gradually accumulate within the walls, reducing porosity and permeability, thereby weakening the PRB's hydraulic interception capacity and increasing the risk of contamination plume bypass. Furthermore, the consumption of active fillers and the reduction in reactive surface area caused by mineral precipitation also reduce the PRB's long-term remediation performance. Therefore, PRBs require replacement or cleaning of the filler material after a period of use. Currently, PRB filler replacement or cleaning is accomplished by first excavating the old filler buried underground using excavation equipment and then directly filling it with new filler, or by cleaning and purifying the old filler before refilling. However, because PRB fillers are mostly loose and granular and interact with the surrounding soil, traditional excavation and replacement methods present challenges such as difficulty replacing partially failed fillers, high construction complexity, the potential for secondary pollution and sidewall collapse, and high costs. Furthermore, because PRBs are mostly fixed structures with fixed dimensions and filler volume, their treatment capacity is limited, and their ability to respond poorly to fluctuations in pollution loads (influent quality and quantity) is limited.

[0003] In summary, the core problems of existing PRB technology include: (1) The fixed structure has great limitations: Traditional PRBs are mostly fixed in design and cannot flexibly adjust the treatment capacity according to changes in water quality and quantity (for example, when the flow rate difference between dry season and rainy season is large, the PRB treatment efficiency fluctuates significantly); (2) The difficulty of replacing the filler: Replacing the filler requires shutting down the machine or dismantling the structure, resulting in interruption of the repair and affecting the continuity of groundwater remediation. For example, the utility model patent with patent publication number CN216377762U discloses a device for remediating organically contaminated groundwater using PRB technology, which includes a pH adjustment tank, a chemical oxidation tank, and a water reservoir arranged in sequence. The pH adjustment tank, the chemical oxidation tank, and the water reservoir are connected by a pipeline, and a circulation pump is installed on the pipeline. An injection well, a PRB filling wall, and a pumping well are arranged in sequence along the flow direction of the organically contaminated groundwater; a clean water pump is provided inside the pumping well, and the water outlet end of the submersible pump is connected to a pumping pipeline. The upper end of the pumping pipeline is connected to the pH adjustment tank, and the upper part of the water reservoir is connected to the injection well through an injection pipe. The utility model can effectively solve the problem of low efficiency in remediating organically contaminated groundwater by combining upstream in-situ injection oxidation, adsorption degradation by the PRB reaction system, and downstream monitoring and extraction treatment. However, the device still has the problem of inconvenient replacement of PRB fillers. Summary of the Invention

[0004] In view of the above problems, the present invention provides an adjustable permeable reactive wall structure and a method for treating pollution plumes.

[0005] The technical solution of the present invention is:

[0006] An adjustable permeable reaction wall structure includes a plurality of stuffing box assemblies arranged side by side, a slide rail located below the stuffing box assemblies, and two symmetrically arranged blocking slides slidably arranged on the slide rail and used for selectively blocking the stuffing box assemblies;

[0007] The stuffing box assembly includes a plurality of PRB stuffing boxes arranged from bottom to top and fixedly connected to each other, a screen is provided at each of the front and rear openings of the PRB stuffing box, an active filler is provided inside the PRB stuffing box, and a slot is provided at the screen extending from the front end of the PRB stuffing box;

[0008] A plurality of inserting plates are provided on the rear side of the blocking slide from bottom to top, and each of the inserting plates is slidably and detachably docked with each of the slots located on the same horizontal plane, so that the corresponding PRB stuffing box remains closed after docking;

[0009] A concrete plate for fixing the stuffing box assembly and the slide rail is provided on both sides and the bottom of the stuffing box assembly and the slide rail.

[0010] Furthermore, the stuffing box assembly includes 4 to 12 groups, each group of the stuffing box assembly includes 6 to 20 PRB stuffing boxes, and a number of porous partitions are evenly spaced inside the PRB stuffing box for filling active fillers, which are 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 construction workload and costs.

[0012] Furthermore, the two blocking slides are driven to slide by two driving motors respectively, and the driving motors are located inside the stratum above the ground or groundwater level, and the output end of the driving motor is provided with a first rotating shaft, and the first rotating shaft is meshed and connected with a first transmission steel chain, and the end directly below the first transmission steel chain is meshed and connected with a second rotating shaft, the rear end of the second rotating shaft is rotatably connected to the front side wall of the concrete slab, and the front end of the second rotating shaft is meshed and connected with a second transmission steel chain, the second transmission steel chain extends horizontally toward the middle of the stuffing box assembly, and the end of the second transmission steel chain is meshed and connected with a third rotating shaft, the rear end of the third rotating shaft is rotatably connected to the front side wall of the concrete slab, the third rotating shaft is located below the slide rail, and a plurality of T-shaped blocks are fixedly provided on the second transmission steel chain, and the upper rear side of the T-shaped block is fixedly connected to the lower part of the front side wall of the blocking slide.

[0013] Description: The stuffing box assembly is selectively blocked by the blocking slide to form a permeable reaction wall with adjustable permeable area.

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

[0015] Note: The L-shaped block is set to assist in positioning the blocking slide when it moves to both sides.

[0016] The top of the sliding rail is provided with a first sliding groove for allowing the blocking slide to slide and a second sliding groove for allowing the stuffing box assembly to slide. A group of rollers are respectively provided on the front and rear sides of the bottom of the PRB stuffing box located at the bottom, and a limiting groove is provided in the middle of the bottom of the PRB stuffing box located between the two groups of rollers. One side of the limiting groove is an arc-shaped depression, and two bow-shaped clamping blocks are symmetrically provided in the accommodating cavity inside the second slide groove. One end of the bow-shaped clamping block passes through the first slot above the second slide groove and corresponds to the bottom of the two groups of stuffing box assemblies located in the middle, and the other end of the bow-shaped clamping block passes through the second slot above the second slide groove and corresponds to the bottom of the stuffing box assemblies on both sides. The bottom of the bow-shaped clamping block is fixedly connected to the bottom of the accommodating cavity by a number of springs, and the inner sides of the two protrusions of the bow-shaped clamping block are provided with arc depressions for docking with the limiting groove.

[0017] Note: The setting of the bow-shaped clamp block can realize the automatic inward sliding of the stuffing box assembly, making it easy to replace and place.

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

[0019] Note: The hook is provided to facilitate the overall removal of the stuffing box assembly, and the water quality sensor can monitor the groundwater quality in real time so that corresponding adjustment measures can be made.

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

[0021] S1. Determination of the size of the permeable reaction wall: All the stuffing box components together form the permeable reaction wall. By adjusting the blocking position of the two blocking slides, the permeable length, permeable width and permeable height of the permeable reaction 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] Where, T PRB is the thickness of the permeable reactive wall, in m; L PRB is the permeable length of the permeable reaction wall, in m; H PRB is the permeable height of the permeable reaction wall, in m; u is the actual groundwater flow rate through the permeable reaction wall, in m·d -1 ;t R is the residence time required for the pollutant to be reduced to the target concentration level, in d; C0 is the influent concentration of the permeable reaction wall, in mg·L -1; C s is the target effluent concentration of the permeable reaction wall, in mg·L -1 ; k is the first-order reaction rate constant, unit h -1 SF is the safety factor, which is 3 to 5; Q is the groundwater flow through the permeable reaction wall, in m 3 ·d -1 ;t L is the theoretical operating life of the PRB stuffing box, in d; q max The maximum adsorption capacity of PRB active filler for pollutants, unit g·g -1 ; ρ is the dry density of PRB active filler, unit is g·L -1 ;θ is the porosity of PRB active filler;

[0025] S2. Replacement of active filler: When the active filler inside the PRB filler box needs to be replaced, the two filler box assemblies in the middle are taken out as a whole, and the filler box assemblies on both sides slide inward to fill the position of the taken out filler box assemblies. Then, a whole set of filler box assemblies consisting of PRB filler boxes filled with new active filler are placed from both sides of the permeable reaction wall, and so on to complete the replacement of all the filler box assemblies that need to be replaced.

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

[0027] Furthermore, the permeability coefficient of the active filler in S1 is 2 to 10 times the permeability coefficient of the aqueous 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] Note: By optimizing the proportional relationship between the permeability coefficient of the active filler and the permeability coefficient of the aqueous medium surrounding the permeable reaction wall, the particle size of the active filler with the best water permeability efficiency is optimized.

[0029] The beneficial effects of the present invention are:

[0030] (1) The present invention adopts an adjustable assembled permeable reaction wall structure to effectively overcome the problems of insufficient impact load resistance and difficult filler replacement of traditional PRB. In terms of structural design, it adopts a double-gate parallel connection, upper and lower integral series filler boxes and an active filler thickness adjustable structural design concept to ensure that the target pollutants are completely blocked or intercepted in the PRB; in terms of filler design, it adopts a modular design concept of partition replacement and standardized filler boxes to achieve rapid replacement and response of PRB fillers.

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

[0032] (3) The present invention adopts an adjustable assembly permeable reaction wall structure that divides the PRB into multiple modules, each of which can be filled and replaced independently, reducing the construction workload and lowering the cost. Standardized stuffing boxes are used to facilitate on-site assembly and replacement. According to specific groundwater remediation scenarios, target pollutants and pollution loads, customized matching stuffing boxes are provided, including stuffing type, particle size distribution, etc., to ensure that its reactivity and permeability can meet the remediation requirements. The stuffing plastic boxes are developed in a productized, modularized and standardized manner and are mass-produced in factories. Each stuffing box is transported to the site for rapid assembly and is plug-and-play, with good scalability, sustainability and resistance stability. In addition, when the reaction material loses its activity due to adsorption saturation, resulting in a decrease in purification efficiency, the stuffing box filled with the reaction material can be taken out for material recycling and reuse and replaced with new reaction material, and the stuffing replacement can be achieved while maintaining its processing capacity.

[0033] (4) The method of treating pollution plumes by assembling an adjustable permeable reaction wall structure according to the present invention can achieve

[0034] Intelligent monitoring and real-time feedback: sensors are used to monitor the PRB's inlet concentration, outlet concentration, water velocity, flux and other parameters in real time. Based on the monitoring data, when the PRB is broken down (i.e., the packing fails), prompts are given to adjust the PRB structure or replace the packing. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the overall structure of an adjustable assembled permeable reaction wall structure of the present invention;

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

[0037] Figure 3 This is a schematic diagram of the internal structure of a PRB stuffing box equipped with an adjustable permeable reaction wall structure according to the present invention;

[0038] Figure 4 It is a side view of a bottom PRB stuffing box of an assembled adjustable permeable reactive wall structure of the present invention;

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

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

[0041] Figure 7 This is a schematic diagram of the connection structure between the interior of a slide rail and a PRB stuffing box of an adjustable permeable reaction wall structure of the present invention;

[0042] Figure 8 This is an enlarged structural diagram of the connection between the interior of a slide rail and a PRB stuffing box of an adjustable permeable reaction wall structure of the present invention;

[0043] Figure 9 It is a top view of a blocking slide plate assembled with an adjustable permeable reactive wall structure of the present invention;

[0044] Figure 10 It is a side view of an adjustable assembled permeable reaction wall structure of the present invention.

[0045] Among them, 1-stuffing box assembly, 11-PRB stuffing box, 12-screen, 13-slot, 14-roller, 15-limiting slot, 16-hook, 17-porous partition, 2-slide rail, 21-first slide, 22-second slide, 23-cavity, 24-first slot, 25-second slot, 26-spring, 3-blocking slide, 31-insert 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-type block, 7-second transmission steel chain, 71-T-type block, 8-bow-type block, 9-water quality detector. DETAILED DESCRIPTION

[0046] Example 1

[0047] like Figure 1 As shown, an adjustable permeable reaction wall structure includes eight sets of stuffing box assemblies 1 arranged side by side, a slide rail 2 located below the stuffing box assemblies 1, and two symmetrically arranged blocking slides 3 slidably disposed on the slide rail 2 and used for selectively blocking the stuffing box assemblies 1;

[0048] like Figure 2 and Figure 3As shown, the stuffing box assembly 1 includes 8 PRB stuffing boxes 11 arranged from bottom to top and fixedly connected to each other, a screen 12 is provided at each of the front and rear openings of the PRB stuffing box 11, an active filler is provided inside the PRB stuffing box 11, and a plurality of porous partitions 17 are provided at equal intervals inside the PRB stuffing box 11 for filling the active filler, which is a mixture of activated carbon and zeolite in a mass ratio of 1:1. A slot 13 is provided at the front of the PRB stuffing box 11 extending from a front screen 12, a hook 16 is provided on the top of the topmost PRB stuffing box 11, and a water quality sensor 9 is provided on the front side wall of the blocking slide 3;

[0049] The PRB stuffing box 11 uses an ISO standard snap-fit ​​(DIN46267) design interface, supports horizontal and vertical expansion, and is made of UV-resistant modified PP (tensile strength ≥ 30 MPa). The screen 12 features an anti-clogging design: the front and rear walls utilize double-layer stainless steel screens (SS304), secured by laser welding to intercept suspended solids. Rapid assembly technology utilizes a hydraulic assembly machine to complete the box connection on-site. The top cover of the box utilizes a magnetic lock and hinged opening and closing structure, supporting 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 is provided on both sides and the bottom of the stuffing box assembly 1 and the slide rail 2 for fixing the stuffing box assembly 1 and the slide rail 2. A plurality of inserting plates 31 are provided from bottom to top on the rear side of the blocking slide plate 3. Each inserting plate 31 is slidably and detachably docked with each slot 13 located on the same horizontal plane, and after docking, the corresponding PRB stuffing box 11 remains closed.

[0051] like Figure 1 、 Figure 2 and Figure 5As shown, the two blocking slides 3 are driven to slide by two driving motors 5 respectively. The driving motor 5 is located inside the ground or above the groundwater level. The output end of the driving motor 5 is provided with a first rotating shaft 51. The first rotating shaft 51 is meshed and connected with a first transmission steel chain 6. The end just below the first transmission steel chain 6 is meshed and connected 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. The front end of the second rotating shaft 52 is meshed and connected with a second transmission steel chain 7. The second transmission steel chain 7 extends horizontally toward the middle of the stuffing box assembly 1, and the second transmission steel chain 7 extends horizontally toward the middle of the stuffing box assembly 1. The end of the chain 7 is meshedly connected with a third rotating shaft 53, and 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 provided on the second transmission steel chain 7. The rear side of the upper end of the T-shaped block 71 is fixedly connected to the lower part of the front side wall of the blocking slide 3. An L-shaped block 61 is fixedly provided in the middle of the first transmission steel chain 6. A card slot 32 is provided at the upper edge of the blocking slide 3. When the blocking slide 3 slides to both sides, the L-shaped block 61 synchronously descends and docks with the card slot 32. The drive motor 5 is a commercially available high-power motor.

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

[0053] Example 2

[0054] This embodiment differs from embodiment 1 in that:

[0055] There are four groups of stuffing box assemblies 1, each of which includes six PRB stuffing boxes 11 arranged from bottom to top and fixedly connected to each other.

[0056] Example 3

[0057] This embodiment differs from embodiment 1 in that:

[0058] There are 12 groups of stuffing box assemblies 1, each of which includes 20 PRB stuffing boxes 11 arranged from bottom to top and fixedly connected to each other.

[0059] Example 4

[0060] This embodiment differs from embodiment 1 in that:

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

[0062] Example 5

[0063] This embodiment differs from embodiment 1 in that:

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

[0065] Example 6

[0066] This embodiment is a method for treating a pollution plume by assembling an adjustable permeable reactive wall structure according to embodiment 1, comprising the following steps:

[0067] S1. Determine the size of the permeable reaction wall: All the stuffing box assemblies 1 together form a permeable reaction wall. By adjusting the blocking positions of the two blocking slides 3, the permeable length, permeable width, and permeable height of the permeable reaction wall can be adjusted according to actual environmental conditions. The calculation formula is as follows:

[0068] T PRB =u·t R ·SF

[0069]

[0070] Where, T PRB is the thickness of the permeable reactive wall, in m; L PRB is the permeable length of the permeable reaction wall, in m; H PRB is the permeable height of the permeable reaction wall, in m; u is the actual groundwater flow rate through the permeable reaction wall, in m·d -1 ;t R is the residence time required for the pollutant to be reduced to the target concentration level, in d; C0 is the influent concentration of the permeable reaction wall, in mg·L -1 ; C s is the target effluent concentration of the permeable reaction wall, in mg·L -1 ; k is the first-order reaction rate constant, unit h -1 SF is the safety factor, ranging from 3 to 5; Q is the groundwater flow through the permeable reaction wall, in m3·d -1 ;t L is the theoretical operating life of the PRB stuffing box 11, in d; q max The maximum adsorption capacity of PRB active filler for pollutants, unit g·g -1 ; ρ is the dry density of PRB active filler, unit is g·L-1 ;θ is the porosity of PRB active filler;

[0071] The permeability coefficient of the active filler is 8 times the permeability coefficient of the aqueous medium surrounding the permeable reaction wall, and the pore size of the screen 12 is 1 / 3 of the pore size of the active filler;

[0072] S2. Replacement of active filler: When the active filler inside the PRB stuffing box 11 needs to be replaced, the two stuffing box assemblies 1 in the middle are taken out as a whole, and at the same time, the stuffing box assemblies 1 on both sides slide inward to fill the position of the taken out stuffing box assemblies 1, and then a whole group of stuffing box assemblies 1 consisting of PRB stuffing boxes 11 filled with new active filler are placed from both sides of the permeable reaction wall, and so on to complete the replacement of all stuffing box assemblies 1 that need to be replaced.

[0073] Example 7

[0074] This embodiment differs from embodiment 6 in that:

[0075] The permeability coefficient of the active filler is twice the permeability coefficient of the aqueous medium surrounding the permeable reaction wall, and the pore size of the screen 12 is 1 / 3 of the pore size of the active filler.

[0076] Example 8

[0077] This embodiment differs from embodiment 6 in that:

[0078] The permeability coefficient of the active filler is 10 times the permeability coefficient of the aqueous medium surrounding the permeable reaction wall, and the pore size of the screen 12 is 1 / 2 of the pore size of the active filler.

[0079] Working principle: The working principle of an assembled adjustable permeable reaction wall structure of the present invention is briefly described below in combination with the method of the present invention.

[0080] When performing S1, it is necessary to adjust the blocking position of the blocking slide 3, turn on the driving motor 5, and 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 slides 3 to slide inward along the first sliding groove 21, and at the same time, each plugging plate 31 is docked and inserted into each slot 13 to complete the blocking of the screen 12 and prevent water from flowing through.

[0081] When S2 is performed, the stuffing box assembly 1 needs to be replaced, and the hooks 16 on the two stuffing box assemblies 1 in the middle are connected by an external steel wire rope, and the two stuffing box assemblies 1 are lifted out by a winch. At the same time, when the stuffing box assembly 1 is lifted out, the limiting grooves 15 at the bottom of the two stuffing box assemblies 1 on the two most sides are gradually pushed out under the combined action of hydraulic force and the thrust of the spring 26. When the outer end of the bow-shaped clamping block 8 is pushed upward through the second slot 25, the limiting groove 15 is pushed under the action of the arc end surface, and the entire stuffing box assembly 1 is pushed together with the hydraulic action and the buoyancy action, thereby pushing the stuffing box assemblies 1 on both sides to the middle position;

[0082] Subsequently, the new stuffing box assembly 1 with the replaced active filler is placed to the positions on both sides of the permeable reaction wall by a ground winch. After being placed, the bow-shaped block 8 is pressed down. At the same time, the top of the bow-shaped block 8 on the inner side is also squeezed by the limiting groove 15 and descends through the second slot 24, thereby completing the resetting of the bow-shaped block 8 and the replacement of the stuffing box assembly 1.

[0083] Experimental example

[0084] Taking the PRB remediation of contaminated groundwater in a domestic waste landfill as an example, the target pollutant is ammonia nitrogen, and the PRB filler is zeolite with a density of ρ of 1.75t·m -3 , the porosity θ is 0.45, and the adsorption rate constant k of zeolite to ammonia nitrogen is 0.5d -1 The maximum adsorption capacity of zeolite for ammonia nitrogen is 0.016 (g g -1 ), the maximum ammonia nitrogen concentration in the PRB influent was 97.4 mg·L -1 , at 1.5 mg·L -1 The target concentration of ammonia nitrogen in the effluent (i.e., the Class IV groundwater quality standard) is set, and the actual groundwater flow rate u through the PRB is 0.058 m·d -1 , SF takes the empirical value 4, and the above formula is used to calculate T PRB It is 1.93m.

[0085] Assuming the theoretical operating life of the PRB is 5 years, the groundwater flow through the PRB is 52.8m 3 ·d -1 The thickness of the aquifer at the installation location is about 16m. At the same time, according to the requirements, the bottom of the PRB should be embedded 0.6m below the weak permeable layer. Therefore, H PRB is 16.6m, and the T PRB Substituting into the above formula, the required L can be calculated PRB The length, width, and height of the stuffing box assembly 1 are now calculated.

Claims

1. An adjustable permeable reactive wall structure, characterized in that: The invention comprises a plurality of stuffing box assemblies (1) arranged side by side, a slide rail (2) located below the stuffing box assemblies (1), and two symmetrically arranged blocking slide plates (3) slidably arranged on the slide rail (2) and used for selectively blocking the stuffing box assemblies (1); The stuffing box assembly (1) comprises a plurality of PRB stuffing boxes (11) arranged from bottom to top and fixedly connected to each other, a screen (12) is provided at each of the front and rear openings of the PRB stuffing box (11), an active stuffing is provided inside the PRB stuffing box (11), and a slot (13) is provided at one of the screens (12) extending from the front end of the PRB stuffing box (11); The rear side of the blocking slide plate (3) is provided with a plurality of inserting plates (31) from bottom to top, and each of the inserting plates (31) is slidably and detachably docked with each of the slots (13) located on the same horizontal plane, so that the corresponding PRB stuffing box (11) remains closed after docking; A concrete plate (4) for fixing the stuffing box assembly (1) and the slide rail (2) is provided on both sides and the bottom of the stuffing box assembly (1) and the slide rail (2).

2. The adjustable permeable reactive wall structure according to claim 1, characterized in that: The stuffing box assembly (1) includes 4 to 12 groups, each group of the stuffing box assembly (1) includes 6 to 20 PRB stuffing boxes (11), and a plurality of porous partitions (17) are evenly spaced inside the PRB stuffing boxes (11) for filling active fillers, wherein the active fillers are one or more of zero-valent iron, activated carbon and zeolite.

3. The adjustable permeable reactive wall structure according to claim 1, characterized in that: The two blocking slide plates (3) are driven to slide by two driving motors (5) respectively. The driving motors (5) are located inside the ground or above the groundwater level. The output end of the driving motor (5) is provided with a first rotating shaft (51). The first rotating shaft (51) is meshedly connected with a first transmission steel chain (6). The end directly below the first transmission steel chain (6) is meshedly connected 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). The front end of the second rotating shaft (52) is meshedly connected to the front side wall of the concrete slab (4). A second transmission steel chain (7) is connected, the second transmission steel chain (7) extends horizontally toward the middle of the stuffing box assembly (1), and the end of the second transmission steel chain (7) is meshedly connected to 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), and a plurality of T-shaped blocks (71) are fixedly provided on the second transmission steel chain (7), and the rear side of the upper end of the T-shaped block (71) is fixedly connected to the lower part of the front side wall of the blocking slide plate (3).

4. The adjustable permeable reactive wall structure according to claim 3, characterized in that: There are 2 to 3 T-shaped blocks (71), an L-shaped block (61) is fixedly provided in the middle of the first transmission steel chain (6), and a card slot (32) is provided at the upper edge of the blocking slide (3). When the blocking slide (3) slides to both sides, the L-shaped block (61) is synchronously lowered and docked with the card slot (32).

5. The adjustable permeable reactive wall structure according to claim 1, characterized in that: The slide rail (2) includes a first slide groove (21) for sliding the blocking slide plate (3) and a second slide groove (22) for sliding the stuffing box assembly (1). A group of rollers (14) are respectively provided on the front and rear sides of the bottom of the PRB stuffing box (11) at the bottom. A limiting groove (15) is provided in the middle of the bottom of the PRB stuffing box (11) located between the two groups of rollers (14). One side of the limiting groove (15) is an arc-shaped depression. Two bow-shaped blocks ( 8), one end of the bow-shaped clamping block (8) passes through the first slot (24) and exits above the second slide slot (22) and corresponds to the bottom of the two groups of stuffing box assemblies (1) located in the middle, and the other end of the bow-shaped clamping block (8) passes through the second slot (25) and exits above the second slide slot (22) and corresponds to the bottom of the stuffing box assemblies (1) located on both sides, the bottom of the bow-shaped clamping block (8) is fixedly connected to the bottom of the accommodating cavity (23) through a plurality of springs (26), and the inner sides of the two protrusions of the bow-shaped clamping block (8) are both provided with arc-shaped recesses for docking with the limiting slot (15).

6. The adjustable permeable reactive wall structure according to claim 1, characterized in that: A hook (16) is provided on the top of the PRB stuffing box (11) located at the top, and a water quality sensor (9) is provided on the front side wall of the blocking slide (3).

7. A method for treating pollution plumes by assembling an adjustable permeable reactive wall structure according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Determination of the size of the permeable reaction wall: All the stuffing box components (1) together form a permeable reaction wall. By adjusting the blocking positions of the two blocking slides (3), the permeable length, permeable width and permeable height of the permeable reaction wall can be adjusted according to the actual environmental conditions. The calculation formula is as follows: T PRB =u·t R ·SF Where, T PRB is the thickness of the permeable reaction wall, in m; L PRB is the permeable length of the permeable reaction wall, in m; H PRB is the permeable height of the permeable reaction wall, in m; u is the actual groundwater flow rate through the permeable reaction wall, in m·d -1 ;t R is the residence time required for the pollutant to be reduced to the target concentration level, in d; C0 is the influent concentration of the permeable reaction wall, in mg·L -1 ; C s is the target effluent concentration of the permeable reaction wall, in mg·L -1 ; k is the first-order reaction rate constant, unit h -1 ; SF is the safety factor, ranging from 3 to 5; Q: Groundwater flow through the permeable reaction wall, unit: m 3 ·d -1 ; t L is the theoretical operating life of the PRB stuffing box (11), in d; q max The maximum adsorption capacity of PRB active filler for pollutants, unit g·g -1 ; ρ is the dry density of PRB active filler, unit is g·L -1 ;θ is the porosity of PRB active filler; S2. Replacement of active filler: When the active filler inside the PRB filler box (11) needs to be replaced, the two filler box assemblies (1) located in the middle are taken out as a whole, and the filler box assemblies (1) located on both sides are slid inward to fill the position of the taken out filler box assembly (1), and then a whole set of filler box assemblies (1) consisting of PRB filler boxes (11) filled with new active filler are placed from both sides of the permeable reaction wall, and so on to complete the replacement of all the filler box assemblies (1) that need to be replaced.

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

9. The method for treating pollution plumes by assembling an adjustable permeable reactive wall structure according to claim 7, characterized in that: The permeability coefficient of the active filler in the S1 is 2 to 10 times the permeability coefficient of the aqueous 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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