Groundwater remediation method and system based on multi-stage reaction wall

Abstract

The present invention discloses a groundwater remediation method and system based on a multi-stage reaction wall. The groundwater remediation method based on the multi-stage reaction wall includes: collecting concentration data of the contaminated area, determining whether there is a high-concentration contamination area in the groundwater contamination plume based on a preset concentration threshold; spraying a reaction column group formed by slow-release microspheres in the high-concentration contamination area to remediate the groundwater; setting up a multi-stage reaction wall downstream of the groundwater contamination plume and providing an electrode array to generate a voltage gradient, thereby promoting the migration of groundwater pollutants to the multi-stage reaction wall, so that the multi-stage reaction wall adsorbs or removes heavy metals and organic matter from the groundwater pollutants; collecting reaction data from the multi-stage reaction wall, and performing remediation on the reaction medium if the reaction data is abnormal. The present invention selects a groundwater remediation method based on the concentration data of the groundwater pollutants, thereby improving the groundwater remediation effect.

Description

Technical Field

[0001] The present invention relates to the technical field of groundwater pollution remediation, and in particular to a groundwater remediation method and system based on a multi-stage reaction wall. Background Art

[0002] With the acceleration of industrialization and urbanization, groundwater pollution has become a major environmental issue of global concern. Due to factors such as the illegal discharge of industrial wastewater and the leakage of domestic sewage, large amounts of heavy metals and organic pollutants seep into underground aquifers, causing excessive concentrations of heavy metal ions in groundwater and irreversible damage to ecosystems.

[0003] Permeable Reactive Barrier (PRB) technology is a passive in-situ remediation technique for groundwater pollution control. A PRB containing a reactive medium is placed downstream of a contaminated plume and perpendicular to the groundwater flow. This allows contaminated groundwater to flow through the PRB due to its hydraulic gradient. The PRB removes contaminants from the groundwater through precipitation, adsorption, and degradation, thereby achieving groundwater pollution control.

[0004] Currently, groundwater remediation requires selecting different reactive media to fill the PRBs, based on the type of groundwater contaminants and the remediation objectives, to remove the contaminants. However, existing reactive media materials have limited functionality, and the permeable reactive wall structure is monolithic. This makes it impossible to tailor the remediation method based on the concentration of groundwater contaminants, resulting in poor remediation results. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a groundwater remediation method and system based on a multi-stage reaction wall, aiming to solve the problem that the existing technology cannot specifically select remediation methods according to the concentration of pollutants in the groundwater, resulting in poor groundwater remediation effect.

[0006] The present invention discloses a groundwater remediation method based on a multi-stage reaction wall, comprising: collecting concentration data of groundwater pollutants in a contaminated area;

[0007] If the concentration data is greater than the preset concentration threshold, the polluted area is marked as a high-concentration pollution area, and a reaction column group formed by slow-release microspheres is sprayed into the high-concentration pollution area. The slow-release microspheres are used to adsorb or remove groundwater pollutants;

[0008] A multi-stage reaction wall is set up downstream of the groundwater pollution plume, wherein the multi-stage reaction wall includes a first filtration layer, a core reaction layer, a biological enhancement layer and a second filtration layer stacked in sequence;

[0009] An electrode array is provided, and a voltage gradient is generated by the electrode array, wherein the voltage gradient is used to promote the migration of groundwater pollutants to the multi-stage reaction wall, so that the multi-stage reaction wall adsorbs or removes heavy metals and organic matter in the groundwater pollutants;

[0010] The reaction data of the multi-stage reaction wall is collected, and when the reaction data is abnormal, the reaction medium in the core reaction layer and the reaction medium in the bio-enhanced layer are repaired.

[0011] Preferably, if the concentration data is less than or equal to a preset concentration threshold, the polluted area is marked as a low-concentration pollution area;

[0012] A multi-stage reaction wall is set up downstream of the groundwater pollution plume, wherein the multi-stage reaction wall includes a first filtration layer, a core reaction layer, a biological enhancement layer and a second filtration layer stacked in sequence;

[0013] An electrode array is provided, and a voltage gradient is generated by the electrode array, wherein the voltage gradient is used to promote the migration of groundwater pollutants to the multi-stage reaction wall, so that the multi-stage reaction wall adsorbs or removes heavy metals and organic matter in the groundwater pollutants;

[0014] The reaction data of the multi-stage reaction wall is collected, and when the reaction data is abnormal, the reaction medium in the core reaction layer and the reaction medium in the bio-enhanced layer are repaired.

[0015] Preferably, before the reaction column group formed by the slow-release microspheres is sprayed into the high-concentration pollution area, the method further includes: setting a control device in the high-concentration pollution area, the control device being used to control the pH value of the high-concentration pollution area; the control device has a built-in slow-release material, and the slow-release material includes at least one of calcium oxide and sodium bicarbonate.

[0016] Preferably, a pH-responsive swelling layer is provided on the surface of the sustained-release microspheres, and the pH-responsive swelling layer controls the release rate of the sustained-release microspheres according to the pH of the high-concentration contaminated area;

[0017] The slow-release microspheres are persulfate microspheres or zero-valent iron microspheres. The persulfate microspheres are used to carry out a persulfate oxidation reaction with groundwater pollutants, and the zero-valent iron microspheres are used to carry out a zero-valent iron-mediated reduction reaction with groundwater pollutants.

[0018] Preferably, the first filter layer comprises mixed aggregate, the particle size of the mixed aggregate is 2 to 4 mm, the mixed aggregate comprises diatomaceous earth aggregate and steel slag aggregate, the diatomaceous earth aggregate accounts for 60% of the weight of the mixed aggregate, and the steel slag aggregate accounts for 40% of the weight of the mixed aggregate;

[0019] The core reaction layer includes zero-valent iron biochar composite microcapsules, which are coated with a sodium alginate film of a preset thickness. The zero-valent iron biochar composite microcapsules are used to adsorb or reduce heavy metals in groundwater pollutants.

[0020] The bio-enhanced layer includes a degradation bacterial agent, which is fixed based on the microporous structure of agar and activated carbon and is used to decompose organic matter in groundwater pollutants;

[0021] The second filter layer includes mixed aggregate, the particle size of the mixed aggregate is 2 to 4 mm, the mixed aggregate includes diatomaceous earth aggregate and steel slag aggregate, the diatomaceous earth aggregate accounts for 60% of the weight of the mixed aggregate, and the steel slag aggregate accounts for 40% of the weight of the mixed aggregate.

[0022] Preferably, collecting reaction data of the multi-stage reaction wall includes:

[0023] Obtaining redox potential, which is collected based on a redox potential sensor in the core reaction layer;

[0024] Obtain dissolved oxygen concentration, which is collected based on the dissolved oxygen sensor in the bio-augmented layer.

[0025] Preferably, in the case of abnormal reaction data, repairing the reaction medium in the core reaction layer and the reaction medium in the bio-augmentation layer includes:

[0026] When the redox potential change trend is different from the preset potential change trend, ultrasonic waves of a preset ultrasonic frequency are emitted to the core reaction layer, where the ultrasonic waves are emitted by an ultrasonic generator disposed inside the core reaction layer;

[0027] When the dissolved oxygen concentration is less than a preset oxygen concentration threshold, oxygen is supplied to the biological enhancement layer. The oxygen is supplied by an aeration device, which is arranged on the top of the biological enhancement layer.

[0028] Preferably, an electrode array is provided, and a voltage gradient is generated using the electrode array, comprising:

[0029] At least three pairs of electrode groups are set, with the distance between two adjacent pairs of electrode groups being 3 to 5 meters, each pair of electrode groups being respectively set as a positive electrode and a negative electrode, with adjacent electrodes being opposite electrodes;

[0030] By controlling the voltage amplitude and phase of the electrode group, a voltage gradient is generated, and by periodically switching the positive and negative electrodes of the electrode group, an alternating electric field is generated. The voltage gradient and alternating electric field are used to increase the migration rate of groundwater pollutants.

[0031] Preferably, the groundwater remediation method based on the multi-stage reaction wall further comprises: calculating the removal rate of groundwater pollutants based on the collected concentration data of groundwater pollutants;

[0032] In the event of abnormal response data, an alarm message is generated.

[0033] The present invention also discloses a groundwater remediation system based on a multi-stage reaction wall, comprising: a data acquisition module configured to: collect concentration data of groundwater pollutants in a contaminated area, and collect reaction data of the multi-stage reaction wall, the multi-stage reaction wall comprising a first filtration layer, a core reaction layer, a bio-enhanced layer, and a second filtration layer stacked in sequence, the reaction data comprising the redox potential of the core reaction layer and the dissolved oxygen concentration of the bio-enhanced layer;

[0034] The concentration response module is configured to: if the concentration data is greater than a preset concentration threshold, mark the contaminated area as a high-concentration contaminated area and spray a reaction column group formed by slow-release microspheres into the high-concentration contaminated area, wherein the slow-release microspheres are used to adsorb or remove groundwater pollutants; and if the concentration data is less than or equal to the preset concentration threshold, mark the contaminated area as a low-concentration contaminated area;

[0035] The hydraulic control module is configured to: generate a voltage gradient based on the electrode array to promote the migration of groundwater contaminants toward the multi-stage reaction wall;

[0036] A multi-stage reactive wall configured to: adsorb or remove heavy metals and organic matter from groundwater contaminants;

[0037] The operation and maintenance control module is configured to: in the event of abnormal reaction data, perform repair on the reaction medium in the core reaction layer and the reaction medium in the biological enhancement layer.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. This invention uses collected groundwater pollutant concentration data to flexibly adjust remediation strategies based on the concentration data. When the concentration data is greater than a preset concentration, the groundwater is remediated using a combination of sprayed slow-release microspheres and a multi-stage reaction wall. When the concentration data is less than or equal to the preset concentration, the groundwater is remediated using only the multi-stage reaction wall, thereby achieving targeted remediation of different contaminated areas.

[0040] 2. The present invention generates a voltage gradient through an electrode array and utilizes the electromigration enrichment effect to guide the directional migration of groundwater pollutants to the multi-stage reaction wall, thereby increasing the migration rate of groundwater pollutants and thus improving the remediation effect.

[0041] 3. The present invention determines whether the reaction medium in the multi-stage reaction wall needs to be repaired based on the reaction data of the multi-stage reaction wall, thereby extending the service life of the reaction medium, reducing the replacement frequency, and lowering the operation and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic flow chart of a groundwater remediation method based on a multi-stage reaction wall provided by the present invention;

[0043] Figure 2A schematic structural diagram of a groundwater remediation system based on a multi-stage reaction wall provided by the present invention;

[0044] Figure 3 A vertical cross-sectional schematic diagram of the groundwater remediation experimental device provided by the present invention;

[0045] Figure 4 This is a schematic diagram of the planar layout of the groundwater remediation experimental device provided by the present invention.

[0046] Reference numerals:

[0047] 1. Surface filtration layer; 2. Core reaction layer; 3. Bio-enhancement layer; 4. Electrode array; 5. Reaction column group; 6. High-concentration pollution area; 7. pH control well; 8. ORP sensor; 9. DO sensor; 10. Ultrasonic generator; 11. Aeration device; 12. Low-permeability geological body; 13. Relatively impermeable geological body; 14. Upstream groundwater recharge area; 15. Downstream groundwater catchment area; 16. Peristaltic pump. DETAILED DESCRIPTION

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0049] The present invention will be described in further detail below with reference to the accompanying drawings.

[0050] like Figure 1 As shown, an embodiment of the present invention provides a groundwater remediation method based on a multi-stage reaction wall, comprising:

[0051] S1. Collect concentration data of groundwater pollutants in the polluted area.

[0052] In this embodiment, groundwater pollutants may be heavy metal pollutants, organic pollutants and other impurities. By collecting concentration data of the polluted area, the degree of pollution in the polluted area can be evaluated, and then the groundwater remediation method of the polluted area can be selected in a targeted manner according to the degree of pollution.

[0053] S21. If the concentration data is greater than a preset concentration threshold, the polluted area is marked as a high-concentration pollution area, and a reaction column group formed by slow-release microspheres is sprayed toward the highly polluted area.

[0054] In this embodiment, the groundwater pollutants corresponding to the high-concentration pollution area are complex in type and high in concentration. By spraying the reaction column group into the high-concentration pollution area, the slow-release microspheres in the reaction column group can be used to adsorb or remove the groundwater pollutants.

[0055] In order to improve the effectiveness of the slow-release microspheres in the reaction column group in adsorbing or removing groundwater pollutants, it is necessary to control the pH of the high-concentration contaminated area within a preset pH range, for example, a preset pH range of 6.5 to 7.5.

[0056] Based on this, this embodiment installs a control device within a high-concentration contaminated area. This device contains a slow-release material, which includes at least one of calcium oxide and sodium bicarbonate. Through the reaction between the slow-release material and groundwater, the pH level in the high-concentration contaminated area can be regulated, thereby improving the effectiveness of groundwater remediation. For example, the control device can be one or more pH wells.

[0057] In this embodiment, a pH-responsive swelling layer is provided on the surface of the slow-release microspheres. The pH-responsive swelling layer is used to control the release rate of the slow-release microspheres according to the pH of the high-concentration contaminated area. The slow-release microspheres are persulfate microspheres or zero-valent iron microspheres. The persulfate microspheres are used to undergo a persulfate oxidation reaction with groundwater pollutants, thereby degrading the persulfate pollutants in the groundwater pollutants, and the zero-valent iron microspheres are used to undergo a zero-valent iron-mediated reduction reaction with the groundwater pollutants. In this way, during the release process of the slow-release microspheres, heavy metals and organic pollutants in the groundwater pollutants are gradually adsorbed or removed.

[0058] S3. Set up a multi-stage reaction wall downstream of the groundwater pollution plume.

[0059] In this embodiment, the multi-stage reaction wall includes a first filtration layer, a core reaction layer, a bioreinforcement layer, and a second filtration layer stacked in sequence. The first filtration layer includes a mixed aggregate having a particle size of 2 to 4 mm and comprising diatomaceous earth aggregate and steel slag aggregate, with the diatomaceous earth aggregate accounting for 60% of the weight of the mixed aggregate and the steel slag aggregate accounting for 40% of the weight of the mixed aggregate.

[0060] The core reaction layer consists of zero-valent iron-biochar composite microcapsules, coated with a sodium alginate membrane of a predetermined thickness. These microcapsules are designed to adsorb or remove heavy metals from groundwater contaminants. For example, the microcapsules contain iron and carbon in a 1:3 weight ratio, and the sodium alginate membrane is 50µm thick.

[0061] The bio-enhanced layer includes a degradation agent, which is fixed in the microporous structure of agar and activated carbon and is used to decompose organic matter in groundwater pollutants. For example, the degradation agent is a commercial VOCs degradation agent with a cell density of > .

[0062] The second filter layer includes mixed aggregate, the particle size of the mixed aggregate is 2 to 4 mm, the mixed aggregate includes diatomaceous earth aggregate and steel slag aggregate, the diatomaceous earth aggregate accounts for 60% of the weight of the mixed aggregate, and the steel slag aggregate accounts for 40% of the weight of the mixed aggregate.

[0063] S4. Setting up an electrode array and using the electrode array to generate a voltage gradient, the voltage gradient is used to promote the migration of groundwater pollutants to the multi-stage reaction wall.

[0064] In this embodiment, the electrode array includes at least three pairs of electrode groups, and the distance between two adjacent pairs of electrode groups is 3 to 5 meters, wherein each pair of electrode groups is respectively configured as a positive electrode and a negative electrode, and adjacent electrodes are opposite electrodes.

[0065] By controlling the voltage amplitude and phase of the electrode group to generate a voltage gradient, and periodically switching the positive and negative electrodes of the electrode group to generate an alternating electric field, the voltage gradient and alternating electric field promote the migration of groundwater contaminants toward the multi-stage reaction wall, thereby improving the efficiency of groundwater remediation.

[0066] It's important to note that diatomaceous earth aggregate has a porous structure, allowing contaminants to be trapped within its pores through physical adsorption. The alkaline content of steel slag aggregate can adjust the pH of groundwater, creating a more alkaline environment that favors the precipitation of contaminants. This allows the first filter layer to absorb groundwater contaminants, achieving groundwater remediation.

[0067] Zero-valent iron-biochar composite microcapsules can reduce heavy metal ions in groundwater to low-valent or zero-valent metals, making pollutants easier to precipitate. Biochar has a porous structure and a large amount of surface charge, which can maintain the reducing effect of zero-valent iron and enhance the remediation effect of pollutants through surface adsorption and other effects.

[0068] The microorganisms in VOCs degrading agents can use VOCs as a carbon source and energy source for metabolism, thereby decomposing groundwater pollutants into harmless small molecules such as carbon dioxide and water.

[0069] In this way, the use of multi-stage reaction walls to repair groundwater can effectively remove different pollutants in groundwater, significantly improve the repair efficiency, and ensure the repair effect.

[0070] S5. Collect reaction data of the multi-stage reaction wall, and if the reaction data is abnormal, perform repair on the reaction medium in the core reaction layer and the reaction medium in the bio-enhanced layer.

[0071] In this embodiment, the reaction data includes redox potential and dissolved oxygen concentration. In the process of collecting reaction data of the multi-stage reaction wall, the redox potential and the dissolved oxygen concentration are obtained, wherein the redox potential is collected based on the redox potential sensor in the core reaction layer, and the dissolved oxygen concentration is collected based on the dissolved oxygen sensor in the biological enhancement layer.

[0072] Then, repair is performed on the reaction medium in the core reaction layer and the reaction medium in the biological enhancement layer according to the reaction data.

[0073] In this embodiment, the reaction data can be used to characterize the usage of the reaction medium. Since the core reaction layer removes groundwater pollutants through redox reactions, the redox potential of the core reaction layer is monitored using a redox potential sensor. When the reaction medium in the core reaction layer is about to be exhausted, the redox potential change trend is different from the preset potential change trend. At this time, the reaction data is abnormal. By setting an ultrasonic transmitter inside the core reaction layer and emitting ultrasonic waves of a preset ultrasonic frequency, the passivation layer such as iron hydroxide and iron oxide on the surface of the zero-valent iron microcapsules can be removed, and the zero-valent iron can be exposed again, thereby repairing the reaction medium in the core reaction layer. The preset ultrasonic frequency can be 15 to 28 kHz.

[0074] For example, an ultrasonic generator is placed in the core reaction layer. When the redox potential change trend is contrary to the preset potential change trend, the ultrasonic generator is controlled to emit ultrasonic waves with a frequency of 20KHz to repair the reaction medium in the core reaction layer.

[0075] Furthermore, the degradation agents in the bio-augmentation layer are aerobic and sensitive to dissolved oxygen concentrations. A dissolved oxygen sensor collects the dissolved oxygen concentration in real time and provides feedback on whether the degradation agents need aeration. An aeration device is installed at the top of the bio-augmentation layer. When the dissolved oxygen concentration falls below a preset oxygen concentration threshold, the aeration device delivers oxygen to the bottom of the bio-augmentation layer to increase the dissolved oxygen concentration in the bio-augmentation layer, thereby preventing the degradation agents from being inactivated due to lack of oxygen.

[0076] S22. If the concentration data is less than or equal to the preset concentration threshold, the polluted area is marked as a low-concentration pollution area.

[0077] In this embodiment, if the contaminated area is low-concentration, there is no need to spray a reaction column group formed by slow-release microspheres. A multi-stage reaction wall is set up downstream of the groundwater contamination plume. The multi-stage reaction wall includes a first filtration layer, a core reaction layer, a bio-augmentation layer, and a second filtration layer stacked in sequence. An electrode array is provided and used to generate a voltage gradient. The voltage gradient is used to promote the migration of groundwater pollutants toward the multi-stage reaction wall, so that the multi-stage reaction wall adsorbs or removes heavy metals and organic matter from the groundwater pollutants. Reaction data from the multi-stage reaction wall is collected, and if the reaction data is abnormal, the reaction medium in the core reaction layer and the reaction medium in the bio-augmentation layer are repaired.

[0078] The above process has the same effect as steps S3, S4 and S5, and will not be repeated here.

[0079] In this embodiment, the pollutant removal rate is calculated based on the collected concentration data of groundwater pollutants, and an alarm prompt message is generated when the response data is abnormal.

[0080] For example, a random forest algorithm can be used to generate material failure warnings based on reaction data. This warning is used to indicate the failure of the reaction medium. Another example is the use of a non-dominated sorting genetic algorithm to calculate the amount of reaction medium to be added. Another example is the use of a modular groundwater flow model to simulate the distribution of groundwater flow fields.

[0081] In this way, through concentration monitoring and intelligent regulation, precise control and efficient management of the groundwater remediation process can be achieved, the remediation effect of groundwater pollutants can be mastered, and intelligent alarms can be issued when the reaction medium in the multi-stage reaction wall fails, thereby reducing operation and maintenance costs.

[0082] like Figure 2 As shown, an embodiment of the present invention also provides a groundwater remediation system based on a multi-stage reaction wall, including a data acquisition module 201, a concentration response module 202, a hydraulic regulation module 203, a multi-stage reaction wall 204 and an operation and maintenance control module 205.

[0083] The data acquisition module 201 is configured to: collect concentration data of groundwater pollutants in the contaminated area, and collect reaction data of a multi-stage reaction wall, which includes a first filtration layer, a core reaction layer, a biological enhancement layer and a second filtration layer stacked in sequence, and the reaction data includes the redox potential of the core reaction layer and the dissolved oxygen concentration of the biological enhancement layer.

[0084] The concentration response module 202 is configured to: if the concentration data is greater than a preset concentration threshold, mark the contaminated area as a high-concentration contaminated area, and spray a reaction column group formed by slow-release microspheres into the high-concentration contaminated area. The slow-release microspheres are used to adsorb or remove groundwater pollutants; and if the concentration data is less than or equal to the preset concentration threshold, mark the contaminated area as a low-concentration contaminated area.

[0085] The hydraulic control module 203 is configured to generate a voltage gradient based on the electrode array to promote the migration of groundwater pollutants to the multi-stage reaction wall 204.

[0086] The multi-stage reaction wall 204 is configured to adsorb or remove heavy metals and organic matter from groundwater pollutants.

[0087] The operation and maintenance control module 205 is configured to perform repair on the reaction medium in the core reaction layer and the reaction medium in the bio-augmentation layer when the reaction data is abnormal.

[0088] In order to make the technical solution of the present invention clearer, the following describes in detail the implementation of the present invention through the first embodiment of the groundwater remediation experimental device.

[0089] In the laboratory, the groundwater environment of the contaminated area was simulated to be contaminated by heavy metals (hexavalent chromium) and organic pollutants (1,2-dichloroethane). The experimental device was used to simulate the construction of a groundwater remediation system based on a multi-stage reaction wall. Figure 3 and Figure 4 As shown, first, a geological body box with a length of 50 cm, a width of 20 cm, and a height of 20 cm is selected, and the geological body box is filled with a clay compacted structure. A low permeability geological body 12 and a relatively impermeable geological body 13 are constructed. The thickness ratio of the low permeability geological body 12 to the relatively impermeable geological body 13 is 4:1, and the permeability coefficient of the low permeability geological body 12 is controlled to be less than cm / s.

[0090] The first simulated groundwater sample was then prepared, and the water sample with an average hexavalent chromium concentration of 20 mg / L and an average 1,2-dichloroethane concentration of 30 mg / L was injected into the simulated formation and cured for 7 days. No water flow slope was applied during the curing process to ensure the diffusion of the pollution plume, thereby forming a low-concentration pollution area.

[0091] A water supply connection hole with a hole diameter of 5 mm is set at the connection between the low permeability geological body 12 and the upstream water source, and a filter is set to prevent soil loss.

[0092] The upstream water level is set below the low-permeability geological body 12. Above the upstream water level is the upstream groundwater recharge area 14. The downstream water level is controlled by a peristaltic pump 16 to maintain a 1 cm lower level than the upstream level, thereby maintaining the hydraulic gradient. Above the downstream water level is the downstream groundwater catchment area 15.

[0093] A multi-stage reaction wall is constructed. The multi-stage reaction wall is a permeable reaction wall composed of four structural layers. From the upstream to the downstream direction of the water flow, there are surface filter layer 1 (i.e., the first filter layer), core reaction layer 2, bio-enhanced layer 3 and surface filter layer 1 (i.e., the second filter layer). Among them, the surface filter layer 1 is filled with 60wt% diatomaceous earth / steel slag aggregate with a particle size of 3mm. The first filter layer is 2cm thick. The core reaction layer 2 is filled with zero-valent iron microcapsules, specifically Fe 0 @BC microcapsules, in which Fe 0 The @BC microcapsules have an iron-carbon mass ratio of 1:3 and are coated with a 50µm thick sodium alginate membrane. The core reaction layer 2 is 2cm thick. The bio-enhancement layer 3 is filled with agar-activated carbon microporous structure immobilized with commercial VOCs-degrading bacteria, with a bacterial density of > The thickness of the bioreinforcement layer 3 is 2 cm. The second filter layer has the same filler and thickness as the first filter layer.

[0094] An ultrasonic generator 10 and an ORP sensor 8 (i.e., an oxidation-reduction potential sensor) were installed in the core reaction layer 2. DO sensors 9 (i.e., dissolved oxygen sensors) and an aeration device 11 were cross-plated in the bioaugmentation layer 3. Three ORP sensors 8 were installed, with a 5 cm interval between adjacent ones. Three DO sensors 9 were installed, with a 5 cm interval between adjacent ones.

[0095] Five groups of electrode arrays 4 were set at a spacing of 4 cm to form a voltage gradient of 0.8 V / cm. The migration and enrichment of pollutants were promoted by an alternating electric field (frequency 1 Hz, voltage 1 V). The migration rate of pollutants was 0.8 m / d, and the redox potential and dissolved oxygen concentration were collected in real time during the simulation operation.

[0096] When the redox potential rises to a preset potential threshold, the ultrasonic frequency of the ultrasonic generator 10 is set to 20 KHz, and when the dissolved oxygen concentration is less than the preset oxygen concentration threshold, the aeration device 11 is started.

[0097] After 30 days of operation, water samples were collected from the pollution source area. Hexavalent chromium concentrations dropped below 1.1 mg / L, and 1,2-dichloroethane concentrations dropped below 2.3 mg / L. This resulted in a calculated heavy metal removal rate exceeding 94%, and a VOC degradation rate exceeding 92%. Neither hexavalent chromium nor 1,2-dichloroethane was detected in the filter layer on the downstream barrier wall. This demonstrates that, for groundwater remediation in low-concentration areas, the use of a multi-stage reaction wall to adsorb or remove groundwater pollutants can achieve significant results.

[0098] In the second embodiment of the groundwater remediation experimental device, the configuration of the first simulated groundwater sample was modified to produce a second simulated groundwater sample. The simulation process of the remaining experimental devices remained unchanged. During the preparation of the second simulated groundwater sample, a water sample with an average hexavalent chromium concentration of 50 mg / L and an average 1,2-dichloroethane concentration of 100 mg / L was injected into the simulated formation and cured for 7 days. During the curing process, no water flow gradient was applied to ensure the diffusion of the contamination plume, thereby forming a high-concentration contamination zone 6.

[0099] Persulfate slow-release microspheres were then injected into the high-concentration contamination area 6 to form a reaction column cluster 5. The sulfate slow-release microspheres had a particle size of 100 µm, and the reaction column cluster 5 had a diameter of 1.5 cm. Two horizontally arranged reaction column clusters 5 were set up. A small container simulated a pH control well 7, in which a CaO slow-release material was placed.

[0100] After 30 days of operation, water samples were collected from the pollution source area. The hexavalent chromium concentration in the samples dropped below 5 mg / L, and the 1,2-dichloroethane concentration dropped below 3.5 mg / L. The calculated heavy metal chromium removal rate reached over 90%, and the VOC degradation rate reached over 96%. Neither hexavalent chromium nor 1,2-dichloroethane was detected in the filter layer on the downstream barrier wall. This indicates that for groundwater remediation in high-concentration areas, the method of first using a reaction column cluster to adsorb or remove groundwater pollutants, followed by a multi-stage reaction wall, can achieve better groundwater remediation results.

[0101] It can be seen from the above technical solutions that the present invention flexibly adjusts the remediation strategy according to the concentration data of groundwater pollutants collected. When the concentration data is greater than the preset concentration, the groundwater is repaired by combining the injection of slow-release microspheres and the multi-stage reaction wall. When the concentration data is less than or equal to the preset concentration, only the multi-stage reaction wall is used to repair the groundwater, thereby achieving targeted remediation of different polluted areas. And by utilizing the electromigration enrichment effect, the groundwater pollutants are guided to migrate directionaly to the multi-stage reaction wall, and the migration rate of the groundwater pollutants is increased, thereby improving the remediation effect. And according to the reaction data of the multi-stage reaction wall, it is judged whether the reaction medium in the multi-stage reaction wall needs to be repaired, thereby extending the service life of the reaction medium, reducing the replacement frequency, and reducing the operation and maintenance costs.

[0102] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A groundwater remediation method based on a multi-stage reaction wall, characterized in that: include: Collecting concentration data of groundwater pollutants in contaminated areas; If the concentration data is greater than a preset concentration threshold, the contaminated area is marked as a high-concentration contaminated area, and a reaction column group formed by slow-release microspheres is sprayed into the high-concentration contaminated area. The slow-release microspheres are used to adsorb or remove the groundwater pollutants. If the concentration data is less than or equal to the preset concentration threshold, the contaminated area is marked as a low-concentration contaminated area. A multi-stage reaction wall is set up downstream of the groundwater pollution plume, wherein the multi-stage reaction wall includes a first filtration layer, a core reaction layer, a bio-enhancement layer and a second filtration layer stacked in sequence; An electrode array is provided, and a voltage gradient is generated by the electrode array, wherein the voltage gradient is used to promote the migration of the groundwater pollutants to the multi-stage reaction wall, so that the multi-stage reaction wall adsorbs or removes heavy metals and organic matter in the groundwater pollutants; Collecting reaction data of the multi-stage reaction wall includes: obtaining redox potential, which is collected based on the redox potential sensor in the core reaction layer; obtaining dissolved oxygen concentration, which is collected based on the dissolved oxygen sensor in the bio-augmentation layer; and, in the case where the reaction data is abnormal, performing repair on the reaction medium in the core reaction layer and the reaction medium in the bio-enhancement layer, including: emitting ultrasonic waves of a preset ultrasonic frequency to the core reaction layer when the redox potential change trend is different from the preset potential change trend, the ultrasonic waves being emitted by an ultrasonic generator disposed inside the core reaction layer; When the dissolved oxygen concentration is less than a preset oxygen concentration threshold, oxygen is supplied to the bio-enhanced layer. The oxygen is supplied by an aeration device, which is disposed on the top of the bio-enhanced layer.

2. The groundwater remediation method according to claim 1, characterized in that: Before spraying the reaction column group formed by the slow-release microspheres into the high-concentration pollution area, the method further includes: A control device is provided in the high-concentration pollution area, wherein the control device is used to control the pH value of the high-concentration pollution area; The regulating device has a built-in sustained-release material, and the sustained-release material includes at least one of calcium oxide and sodium bicarbonate.

3. The groundwater remediation method according to claim 2, characterized in that: The surface of the sustained-release microspheres is provided with a pH-responsive swelling layer, and the pH-responsive swelling layer controls the release rate of the sustained-release microspheres according to the pH of the high-concentration contaminated area; The slow-release microspheres are persulfate microspheres or zero-valent iron microspheres. The persulfate microspheres are used to undergo a persulfate oxidation reaction with the groundwater pollutants, and the zero-valent iron microspheres are used to undergo a zero-valent iron-mediated reduction reaction with the groundwater pollutants.

4. The groundwater remediation method according to claim 1, characterized in that: The first filter layer includes mixed aggregate, the particle size of the mixed aggregate is 2 to 4 mm, the mixed aggregate includes diatomaceous earth aggregate and steel slag aggregate, the diatomaceous earth aggregate accounts for 60% of the weight of the mixed aggregate, and the steel slag aggregate accounts for 40% of the weight of the mixed aggregate; The core reaction layer includes zero-valent iron biochar composite microcapsules, the outside of which is wrapped with a sodium alginate film of a preset thickness, and the zero-valent iron biochar composite microcapsules are used to adsorb or reduce heavy metals in the groundwater pollutants; The bio-enhanced layer includes a degradation bacterial agent, which is fixed based on the microporous structure of agar and activated carbon, and is used to decompose organic matter in the groundwater pollutants; The second filter layer includes the mixed aggregate, the particle size of the mixed aggregate is 2 to 4 mm, the mixed aggregate includes diatomaceous earth aggregate and steel slag aggregate, the diatomaceous earth aggregate accounts for 60% of the weight of the mixed aggregate, and the steel slag aggregate accounts for 40% of the weight of the mixed aggregate.

5. The groundwater remediation method according to claim 1, characterized in that: The step of providing an electrode array and utilizing the electrode array to generate a voltage gradient includes: At least three pairs of electrode groups are provided, with a distance between two adjacent pairs of electrode groups of 3 to 5 meters, each pair of electrode groups is respectively provided with a positive electrode and a negative electrode, and adjacent electrodes are provided with opposite electrodes; A voltage gradient is generated by controlling the voltage amplitude and phase of the electrode group, and an alternating electric field is generated by periodically switching the positive and negative electrodes of the electrode group. The voltage gradient and the alternating electric field are used to increase the migration rate of the groundwater pollutants.

6. The groundwater remediation method according to claim 1, characterized in that: Also includes: Calculating the removal rate of groundwater pollutants based on the collected concentration data of the groundwater pollutants; When the response data is abnormal, an alarm message is generated.

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