Heavy metal polluted underground water prevention and control device

Abstract

The utility model discloses a heavy metal polluted underground water prevention and control device for a heterogeneous aquifer, which comprises a PRB (Permeable Reactive Barrier), an activating fluid injection well and a water-proof barrier are sequentially arranged along the flow direction X of polluted underground water, and the two sides of the PRB and the activating fluid injection well are respectively provided with a water-proof barrier perpendicular to the water surface. And the waterproof barriers on the two sides are connected with the two ends of the PRB correspondingly. Activating liquid is arranged in front of the injection well and is arranged on the PRB, so that the activating property and the mobility of heavy metal ions are enhanced, the activated heavy metal ions are continuously dissolved out, the connectivity among medium pores is increased, the medium permeability is improved, the mass transfer problem of heavy metal pollutants in a low-permeability field can be effectively solved, the mobility of the heavy metal ions is increased, and the service life of the heavy metal pollutants is prolonged. The method is generally suitable for a heterogeneous site with both a low-permeability site and a high-permeability site, and is not suitable for a single low-permeability site.

Description

Technical Field

[0001] This utility model relates to the field of groundwater control, and in particular to a device for controlling groundwater contaminated with heavy metals. Background Technology

[0002] The key to addressing heavy metal pollution in groundwater lies in prevention and control. Compared with other groundwater control technologies, permeable reactive barrier (PRB) technology has the advantages of low energy consumption, simple management, and long-term treatment of contaminated groundwater, making it a green and sustainable pollution control technology.

[0003] Chinese patent application CN117023839A discloses a barrier wall-permeable reactive wall combination structure suitable for deep groundwater purification. The low-permeability barrier wall is installed at the downstream groundwater outflow of the landfill. The permeable reactive wall is installed above the middle section of the low-permeability barrier wall. The low-permeability barrier wall is constructed using low-permeability barrier wall materials such as soil-bentonite, cement-bentonite, or grouting curtain. The section of the permeable reactive wall below the water level is filled with reactive fillers such as activated carbon, limestone, or zeolite to remove pollutants from the groundwater. The section of the permeable reactive wall above the water level is filled with non-reactive fillers such as coarse sand or gravel. This scheme employs a combination structure of a large-area low-permeability barrier wall and a small-area permeable reactive wall, which creates a large head difference on both sides of the low-permeability barrier wall. This large head difference drives the contaminated groundwater into the permeable reactive wall without the need for external force, making it easy to operate. It achieves efficient utilization of the filler material and efficient purification of the contaminated water flow, effectively reducing the filtration cost of contaminated groundwater.

[0004] When heavy metals flow through the activated packing zone with groundwater, the activity of the existing PRB reactive wall packing gradually decreases as the reaction proceeds. The deactivated packing is a potential secondary source of pollution for groundwater and can also cause blockage of the reactive packing. The blockage of the reactive packing by the pollution plume makes it difficult to guarantee the remediation effect. Summary of the Invention

[0005] The technical problem to be solved by this utility model is to provide a device for the prevention and control of heavy metal pollution in groundwater, which addresses the shortcomings of existing technologies and ensures the remediation effect.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0007] A groundwater pollution control device for heavy metals includes a PRB reactive wall. An activation liquid injection well and the PRB reactive wall are arranged sequentially along the X direction of groundwater flow. Water barriers are installed perpendicular to the water surface on both sides of the activation liquid injection well, and the water barriers on both sides are connected to the two ends of the PRB reactive wall.

[0008] PRB reactive wall refers to a permeable reactive wall.

[0009] The activation fluid injection well in this application can be the activation fluid injection well disclosed in CN110947752A and CN210764479U.

[0010] Placing the activated well before the PRB can effectively improve the mass transfer problem of heavy metal pollutants in low-permeability fields and increase the mobility of heavy metal ions. It is generally suitable for heterogeneous sites with both low-permeability and high-permeability fields.

[0011] Existing PRB (Potentially Reinforcing Barrier) technology has limitations, including secondary pollution requiring timely replacement of deactivated packing material, slow groundwater recovery efficiency, and a tendency for pollution rebound. To address these drawbacks, a heavy metal contamination groundwater control device is proposed. This device injects a heavy metal activating solution into an activation solution injection well in an upstream low-permeability aquifer contaminated with heavy metals, while the PRB reactive barrier is placed in a downstream high-permeability aquifer. As contaminated groundwater flows through the activation solution injection well, the activating solution continuously flows out of the well, while a certain amount of contaminated water flows out of the well simultaneously, causing the water level in the well to drop. Compared to the groundwater around the well, the total water level in the well is lower, which is equivalent to providing a non-powered drive for the activation of the well. The activation liquid continuously flows out of the well, dissolving the adsorbed, bound, and oxidized heavy metals in the pores of the low-permeability medium. The activation and migration of heavy metal ions are enhanced, and the activated heavy metal ions are continuously dissolved. The connectivity between the pores of the medium increases, and the permeability of the medium is improved. When the activated heavy metal ions flow through the PRB reactive barrier with the groundwater, they are adsorbed, precipitated, and chelated by the packing material in the PRB reactive barrier and removed, and the polluted groundwater is gradually restored.

[0012] In a preferred embodiment of this invention, the PRB reactive wall is composed of multiple independent permeation wells, each filled with a reactive packing module.

[0013] Existing PRB reactive wall packings are typically monolithic, permanent, and non-modular. The modular PRB system of this invention enables the packing to maintain its activity for a long time, be easy to replace, and achieve high repair efficiency and lasting effects.

[0014] In a preferred embodiment of this utility model, the reaction packing module consists of a primary solid waste adsorption packing module, a secondary sedimentation packing module, and a tertiary stabilization packing module, from the outside to the inside.

[0015] The primary solid waste adsorption packing module is filled with one of the following biological wastes: coal gangue, fly ash, red mud, steel slag, blast furnace slag, copper slag, and plant shells / leaves. The secondary sedimentation packing module is filled with one of the following: gypsum, limestone, calcium peroxide, and hydroxyapatite. The tertiary stabilizing packing module is filled with a heavy metal chelating stabilizing material, which can be the heavy metal chelating agent disclosed in CN105949100A or CN107199018A.

[0016] In a preferred embodiment of this utility model, the permeation well is a regular hexagon, and the reaction packing module is a hexagonal prism permeation module.

[0017] In a preferred embodiment of this utility model, in order to facilitate the replacement of the reaction packing module and enhance the effect of PRB in treating heavy metals, the tertiary stabilizing packing module is a triangular prism, the secondary precipitation packing module is a triangular prism fitted on the outside of the tertiary stabilizing packing module, and the primary solid waste adsorption packing module is filled between the permeation well and the secondary precipitation packing module.

[0018] The hexagonal, closely spaced modular PRB significantly improves the utilization rate of active filler, extends its service life, and is easy to replace, resulting in high repair efficiency and long-lasting effects.

[0019] In a preferred embodiment of this invention, the PRB reaction wall is equipped with multiple monitoring wells.

[0020] In a preferred embodiment of this invention, multiple online monitoring wells are provided downstream of the PRB reactive barrier along the X direction of the contaminated groundwater flow.

[0021] In a preferred embodiment of this utility model, the online monitoring well is connected to both a heavy metal online monitoring instrument and a pollution early warning platform.

[0022] In a preferred embodiment of this invention, multiple activation solution injection wells are provided. The number of activation solution injection wells is determined based on the pollution form and heavy metal ion concentration.

[0023] In a preferred embodiment of this invention, the distance between the two water barriers gradually decreases along the X direction of the polluted groundwater flow.

[0024] The water barrier is one or more of the following: soil-bentonite water barrier, plain concrete water barrier, cement curtain grouting wall, and geomembrane wall.

[0025] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0026] (1) The activation solution is placed in the PRB reaction wall before injection into the well. The activation and migration of heavy metal ions are enhanced. The activated heavy metal ions are continuously dissolved, the connectivity between the pores of the medium is increased, and the permeability of the medium is improved. This can effectively improve the mass transfer problem of heavy metal pollutants in low-permeability fields and increase the migration of heavy metal ions. It is generally suitable for heterogeneous sites with both low-permeability and high-permeability fields, but not suitable for single low-permeability sites.

[0027] (2) Activation by injection well is a non-powered activation method compared to existing electric field activation, which saves costs and activation well is easier to implement in engineering compared to electric field activation.

[0028] (3) The modular PRB system flows through three stages of reaction packing in sequence, which can achieve efficient removal of heavy metal ions in groundwater. Attached Figure Description

[0029] Figure 1 This is a structural schematic diagram of an embodiment of the present utility model.

[0030] Figure 2 This is a schematic diagram of the reaction packing module in one embodiment of the present invention. Detailed Implementation

[0031] like Figure 1 As shown, a device for controlling heavy metal contamination in groundwater of heterogeneous aquifers includes an activation liquid injection well 2 and a PRB reaction wall 1 arranged sequentially along the X direction of the contaminated groundwater flow. Water barriers 3 are installed perpendicular to the water surface on both sides of the activation liquid injection well 2, and the water barriers 3 on both sides are connected to the two ends of the PRB reaction wall 1. Multiple activation liquid injection wells 2 are provided.

[0032] An activation solution is injected into well 2. The activation solution is a leaching reagent that effectively dissolves heavy metals or metalloids. It can effectively dissolve adsorbed or bound heavy metals or metalloids in the medium through desorption, dissolution, reduction and coordination exchange mechanisms, thereby enhancing the activation and migration of heavy metal ions.

[0033] The water-retaining barriers are arranged vertically to block the migration and transport of contaminated groundwater to the surrounding environment. The water-retaining barrier 3 is one of the following: a soil-bentonite water-retaining wall, a plain concrete water-retaining wall, a cement curtain grouting wall, or a geomembrane wall. Along the direction of the contaminated groundwater flow X, the distance between the two water-retaining barriers 3 gradually decreases.

[0034] A water barrier is installed downstream of the activation injection well to block the migration and transport of activated contaminated groundwater to the surrounding environment and to divert it to the permeable reaction wall.

[0035] The water barrier is connected to a modular PRB system, which is used to capture activated contaminated groundwater. When the activated heavy metal ions flow through the modular PRB with the groundwater, they are adsorbed, precipitated, and chelated by the PRB's cascade reaction packing material and removed, and the contaminated groundwater is gradually restored.

[0036] like Figure 2 As shown, the PRB reactive wall 1 consists of multiple independent permeation wells 11, each filled with a reactive packing module 12. The reactive packing modules 12, from the outside in, are: a primary solid waste adsorption packing module 121, a secondary sedimentation packing module 122, and a tertiary stabilization packing module 123. The permeation wells 11 are hexagonal, and the reactive packing modules 12 are hexagonal prism permeation modules. The tertiary stabilization packing module 123 is a triangular prism, and the secondary sedimentation packing module 122 is a triangular prism fitted around the tertiary stabilization packing module 123. The primary solid waste adsorption packing module 121 is filled between the permeation wells 11 and the secondary sedimentation packing module 122.

[0037] The PRB reactive wall 1 is equipped with multiple monitoring wells 4. Random monitoring wells are installed between the permeation wells, and the monitoring wells and permeation wells can be used flexibly. The permeation modules in the permeation wells can be removed and used as monitoring wells.

[0038] Along the direction X of the contaminated groundwater flow, multiple online monitoring wells 5 are installed downstream of the PRB reactive barrier 1. These online monitoring wells 5 are connected to an online heavy metal monitor and a pollution early warning platform, respectively. The presence of these online monitoring wells downstream of the reactive barrier facilitates continuous sampling and testing of pollutant concentrations to determine the activity of the reactive packing material. When the heavy metal concentration in the downstream online monitoring well exceeds the alarm threshold, the pollution early warning platform will sound an alarm. In this case, samples need to be taken from the monitoring wells between the permeation wells for analysis to determine which module needs replacement, thus requiring the replacement of the permeation material.

Claims

1. A device for controlling heavy metal pollution in groundwater, comprising a PRB reactive barrier (1), characterized in that, An activation liquid injection well (2) and a PRB reaction wall (1) are sequentially arranged along the X direction of the polluted groundwater flow. Water barriers (3) are installed on both sides of the activation liquid injection well (2) perpendicular to the water surface. The water barriers (3) on both sides are connected to the two ends of the PRB reaction wall (1).

2. The heavy metal pollution groundwater control device according to claim 1, characterized in that, The PRB reactive wall (1) consists of multiple independent permeation wells (11), each filled with a reactive packing module (12).

3. The heavy metal pollution groundwater control device according to claim 2, characterized in that, The reaction packing module (12) consists of, from the outside to the inside, a primary solid waste adsorption packing module (121), a secondary precipitation packing module (122), and a tertiary stabilizing packing module (123).

4. The heavy metal pollution groundwater control device according to claim 3, characterized in that, The permeation well (11) is a regular hexagon, and the reaction packing module (12) is a hexagonal prism permeation module.

5. The heavy metal pollution groundwater control device according to claim 4, characterized in that, The tertiary stabilizing packing module (123) is a triangular prism, the secondary sedimentation packing module (122) is a triangular prism fitted outside the tertiary stabilizing packing module (123), and the primary solid waste adsorption packing module (121) is filled between the permeation well (11) and the secondary sedimentation packing module (122).

6. The heavy metal pollution groundwater control device according to any one of claims 1-5, characterized in that, Multiple monitoring wells (4) are installed in the PRB reaction wall (1).

7. The heavy metal pollution groundwater control device according to any one of claims 1-5, characterized in that, Along the direction of the contaminated groundwater flow X, multiple online monitoring wells (5) are set downstream of the PRB reaction wall (1).

8. The heavy metal pollution groundwater control device according to claim 7, characterized in that, The online monitoring well (5) is connected to the heavy metal online monitoring instrument and the pollution early warning platform, respectively.

9. The heavy metal pollution groundwater control device according to any one of claims 1-5, characterized in that, The activation liquid injection well (2) is provided in multiple locations.

10. The heavy metal pollution control device for groundwater according to any one of claims 1-5, characterized in that, Along the direction of the polluted groundwater flow X, the distance between the two water barriers (3) gradually decreases.

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