Underground water remediation method and system based on multi-stage reactive barrier

Abstract

The invention discloses an underground water remediation method and system based on a multi-stage reactive barrier, and the method comprises the steps: collecting the concentration data of a pollution region, and judging whether an underground water pollution plume has a high-concentration pollution region or not according to a preset concentration threshold value; spraying a reaction column group formed by the sustained-release microspheres in the high-concentration pollution area to repair the underground water; the method comprises the following steps: arranging a multi-stage reaction wall at the downstream of an underground water pollution plume, and arranging an electrode array to generate a voltage gradient so as to promote underground water pollutants to migrate to the multi-stage reaction wall, so that the multi-stage reaction wall adsorbs or removes heavy metals and organic matters in the underground water pollutants; and collecting reaction data of the multi-stage reaction wall, and repairing the reaction medium under the condition that the reaction data is abnormal. The groundwater remediation mode is selected in a targeted mode according to the concentration data of the groundwater pollutants, and then the remediation effect of the groundwater is improved.

Description

Technical Field

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

[0002] With the acceleration of industrialization and urbanization, the problem of 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, a large amount of heavy metals and organic pollutants seep into the underground aquifer, resulting in the concentration of heavy metal ions in groundwater exceeding the standard, causing irreversible damage to the ecosystem.

[0003] The Permeable Reactive Barrier (PRB) technology is a passive in-situ remediation technology for groundwater pollution control. A permeable reactive wall containing a reaction medium is set downstream of the groundwater pollution plume and perpendicular to the groundwater flow. In this way, the contaminated groundwater can pass through the permeable reactive wall under the action of its own hydraulic gradient. The permeable reactive wall can remove pollutants in groundwater through precipitation, adsorption and degradation, thereby achieving the treatment of groundwater pollution.

[0004] Currently, in the process of groundwater remediation, different reaction media need to be selected to fill the PRB according to the types of groundwater pollutants and remediation goals, so as to remove pollutants. However, the reaction medium materials in the existing technology have few functions, and the structure of the permeable reactive wall is single, and it is impossible to select the groundwater remediation method according to the concentration of pollutants in groundwater, resulting in poor groundwater remediation effects. Summary of the Invention

[0005] Aiming at the deficiencies in 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 select a remediation method targeted at the concentration of pollutants in groundwater, resulting in poor groundwater remediation effects.

[0006] The present invention discloses a groundwater remediation method based on a multi-stage reaction wall, including: collecting concentration data of groundwater pollutants in a polluted area; If the concentration data is greater than a preset concentration threshold, mark the polluted area as a high-concentration polluted area, and spray a reaction column group formed by slow-release microspheres into the high-concentration polluted area, and the slow-release microspheres are used to adsorb or remove groundwater pollutants; Set a multi-stage reaction wall downstream of the groundwater pollution plume, and the multi-stage reaction wall includes a first filtration layer, a core reaction layer, a bioaugmentation layer and a second filtration layer stacked in sequence; An electrode array is set up, and a voltage gradient is generated by using the electrode array. The voltage gradient is used to promote the migration of groundwater pollutants towards a multi-stage reaction wall, so that the multi-stage reaction wall adsorbs or removes heavy metals and organic matters in the groundwater pollutants; Reaction data of the multi-stage reaction wall is collected, and when the reaction data is abnormal, the reaction media in the core reaction layer and the reaction media in the bioaugmentation layer are repaired.

[0007] Preferably, if the concentration data is less than or equal to a preset concentration threshold, the polluted area is marked as a low-concentration polluted area; A multi-stage reaction wall is set up downstream of the groundwater pollution plume. The multi-stage reaction wall includes a first filtration layer, a core reaction layer, a bioaugmentation layer, and a second filtration layer stacked in sequence; An electrode array is set up, and a voltage gradient is generated by using the electrode array. The voltage gradient is used to promote the migration of groundwater pollutants towards a multi-stage reaction wall, so that the multi-stage reaction wall adsorbs or removes heavy metals and organic matters in the groundwater pollutants; Reaction data of the multi-stage reaction wall is collected, and when the reaction data is abnormal, the reaction media in the core reaction layer and the reaction media in the bioaugmentation layer are repaired.

[0008] Preferably, before injecting a reaction column group formed by slow-release microspheres into the high-concentration polluted area, it further includes: setting a regulating device in the high-concentration polluted area, and the regulating device is used to regulate the pH value of the high-concentration polluted area; the regulating device is internally provided with a slow-release material, and the slow-release material includes at least one of calcium oxide and sodium bicarbonate.

[0009] Preferably, a pH-responsive swelling layer is provided on the surface of the slow-release microspheres, and the pH-responsive swelling layer controls the release rate of the slow-release microspheres according to the pH value of the high-concentration polluted area; The slow-release microspheres are persulfate microspheres or zero-valent iron microspheres. The persulfate microspheres are used for the oxidation reaction of persulfate with groundwater pollutants, and the zero-valent iron microspheres are used for the reduction reaction mediated by zero-valent iron with groundwater pollutants.

[0010] Preferably, the first filtration layer includes a mixed aggregate. The particle size of the mixed aggregate is 2 to 4 mm. The mixed aggregate includes diatomite aggregate and steel slag aggregate. The diatomite 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 zero-valent iron-biochar composite microcapsules are externally wrapped with a sodium alginate membrane of a preset thickness. The zero-valent iron-biochar composite microcapsules are used for adsorbing or reducing heavy metals in groundwater pollutants; The bioaugmentation layer includes a degradation bacterium agent. The degradation bacterium agent is fixed based on the microporous structure of agar and activated carbon. The degradation bacterium agent is used for decomposing organic matters in groundwater pollutants; The second filter layer includes mixed aggregates with a particle size of 2 to 4 mm. The mixed aggregates include diatomite aggregates and steel slag aggregates. The diatomite aggregates account for 60% of the weight of the mixed aggregates, and the steel slag aggregates account for 40% of the weight of the mixed aggregates.

[0011] Preferably, collecting the reaction data of the multi-stage reaction wall includes: Obtaining the oxidation-reduction potential, which is collected based on the oxidation-reduction potential sensor in the core reaction layer; Obtaining the dissolved oxygen concentration, which is collected based on the dissolved oxygen sensor in the bioaugmentation layer.

[0012] Preferably, in the case of abnormal reaction data, repairing the reaction medium in the core reaction layer and the reaction medium in the bioaugmentation layer includes: In the case where the change trend of the oxidation-reduction potential is different from the preset potential change trend, emitting ultrasonic waves with a preset ultrasonic frequency to the core reaction layer. The ultrasonic waves are emitted by an ultrasonic generator, and the ultrasonic generator is arranged inside the core reaction layer; In the case where the dissolved oxygen concentration is less than the preset oxygen concentration threshold, delivering oxygen to the bioaugmentation layer. The oxygen is delivered by an aeration device, and the aeration device is arranged at the top of the bioaugmentation layer.

[0013] Preferably, setting an electrode array and generating a voltage gradient by using the electrode array includes: Setting at least three pairs of electrode groups, with a distance of 3 to 5 m between adjacent pairs of electrode groups. Each pair of electrode groups is respectively set as a positive electrode and a negative electrode, and the adjacent electrodes are opposite electrodes; By controlling the voltage amplitude and phase of the electrode groups, generating a voltage gradient, and by periodically switching the positive and negative electrodes of the electrode groups, generating an alternating electric field. The voltage gradient and the alternating electric field are used to increase the migration rate of groundwater pollutants.

[0014] Preferably, the groundwater remediation method based on the multi-stage reaction wall further includes: calculating the removal rate of groundwater pollutants based on the collected concentration data of groundwater pollutants; Generating an alarm prompt message in the case of abnormal reaction data.

[0015] The present invention also discloses a groundwater remediation system based on a multi-stage reaction wall, including: a data acquisition module configured to: collect the concentration data of groundwater pollutants in a polluted area, and collect the reaction data of the multi-stage reaction wall. The multi-stage reaction wall includes a first filter layer, a core reaction layer, a bioaugmentation layer, and a second filter layer stacked in sequence. The reaction data includes the oxidation-reduction potential of the core reaction layer and the dissolved oxygen concentration of the bioaugmentation layer; A concentration response module, configured to: if the concentration data is greater than a preset concentration threshold, mark the polluted area as a high-concentration polluted area, and inject a reaction column group formed by slow-release microspheres into the high-concentration polluted area, where 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 polluted area as a low-concentration polluted area; A hydraulic regulation module, configured to: generate a voltage gradient based on an electrode array to promote the migration of groundwater pollutants towards a multi-stage reaction wall; A multi-stage reaction wall, configured to: adsorb or remove heavy metals and organic matters in groundwater pollutants; An operation and maintenance control module, configured to: perform repair on the reaction medium in the core reaction layer and the reaction medium in the bioaugmentation layer in case of abnormal reaction data.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention flexibly adjusts the repair strategy according to the concentration data of the collected groundwater pollutants. When the concentration data is greater than the preset concentration, a combination of injecting slow-release microspheres and a multi-stage reaction wall is used to repair the groundwater. 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 repair of different polluted areas.

[0017] 2. The present invention generates a voltage gradient through an electrode array, utilizes the electro-migration enrichment effect, guides the groundwater pollutants to migrate directionally to the multi-stage reaction wall, and improves the migration rate of the groundwater pollutants, thereby improving the repair effect.

[0018] 3. The present invention determines whether it is necessary to repair the reaction medium in the multi-stage reaction wall according to the reaction data of the multi-stage reaction wall, thereby prolonging the service life of the reaction medium, reducing the replacement frequency, and lowering the operation and maintenance cost. Description of the Drawings

[0019] Figure 1 It is a schematic flow chart of the groundwater repair method based on a multi-stage reaction wall provided by the present invention; Figure 2 It is a schematic structural diagram of the groundwater repair system based on a multi-stage reaction wall provided by the present invention; Figure 3 It is a schematic vertical sectional view of the groundwater repair experimental device provided by the present invention; Figure 4 It is a schematic plan layout diagram of the groundwater repair experimental device provided by the present invention.

[0020] Reference Signs: 1. Surface filtration layer; 2. Core reaction layer; 3. Biological enhancement layer; 4. Electrode array; 5. Reaction column group; 6. High-concentration pollution area; 7. pH regulation well; 8. ORP sensor; 9. DO sensor; 10. Ultrasonic generator; 11. Aeration device; 12. Low-permeability geological body; 13. Relatively water-resistant geological body; 14. Upstream groundwater recharge area; 15. Downstream groundwater catchment area; 16. Peristaltic pump. Specific implementation manners

[0021] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] The present invention will be further described in detail below with reference to the accompanying drawings.

[0023] As Figure 1 shown, the embodiments of the present invention provide a groundwater remediation method based on a multi-stage reaction wall, including: S1. Collect the concentration data of groundwater pollutants in the polluted area.

[0024] In this embodiment, the groundwater pollutants may be heavy metal pollutants, organic pollutants, other impurities, etc. By collecting the concentration data of the polluted area, the pollution degree of the polluted area can be evaluated, and then the groundwater remediation method for the polluted area can be selected specifically according to the pollution degree.

[0025] S21. If the concentration data is greater than the preset concentration threshold, mark the polluted area as a high-concentration pollution area, and inject a reaction column group formed by slow-release microspheres into the highly polluted area.

[0026] In this embodiment, the types of groundwater pollutants corresponding to the high-concentration pollution area are complex and the concentration is high. By injecting 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 groundwater pollutants.

[0027] To improve the effect of the slow-release microspheres in the reaction column group in adsorbing or removing groundwater pollutants, it is necessary to regulate the pH value of the high-concentration pollution area within the preset pH range. For example, the preset pH range is 6.5 to 7.5.

[0028] Based on this, in this embodiment, a regulation device is arranged in the high-concentration pollution area. The regulation device is internally provided with a slow-release material, and the slow-release material includes at least one of calcium oxide and sodium bicarbonate. By reacting the slow-release material with groundwater, the pH value of the high-concentration pollution area can be regulated, thereby improving the effect of groundwater remediation. For example, the regulation device can be one or more pH wells.

[0029] 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 value of the high-concentration pollution area. The slow-release microspheres are persulfate microspheres or zero-valent iron microspheres. Among them, the persulfate microspheres are used to carry out the oxidation reaction of persulfate with groundwater pollutants, thereby degrading the persulfate pollutants in the groundwater pollutants, and the zero-valent iron microspheres are used to carry out the zero-valent iron-mediated reduction reaction with 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.

[0030] S3. Set up a multi-stage reaction wall downstream of the groundwater pollution plume.

[0031] In this embodiment, the multi-stage reaction wall includes a first filtration layer, a core reaction layer, a bioaugmentation layer, and a second filtration layer stacked in sequence. Among them, the first filtration layer includes mixed aggregates, the particle size of the mixed aggregates is 2 to 4 mm, the mixed aggregates include diatomite aggregates and steel slag aggregates, the diatomite aggregates account for 60% of the weight of the mixed aggregates, and the steel slag aggregates account for 40% of the weight of the mixed aggregates.

[0032] The core reaction layer includes zero-valent iron-biochar composite microcapsules. The zero-valent iron-biochar composite microcapsules are externally wrapped with a preset thickness of sodium alginate film. The zero-valent iron-biochar composite microcapsules are used to adsorb or remove heavy metals in groundwater pollutants. For example, the zero-valent iron-biochar composite microcapsules contain iron and carbon, and the weight ratio of iron to carbon is 1:3, and the thickness of the sodium alginate film is 50 µm.

[0033] The bioaugmentation layer includes a degrading bacterium agent. The degrading bacterium agent is fixed based on the microporous structure of agar and activated carbon. The degrading bacterium agent is used to decompose the organic matter in groundwater pollutants. For example, the degrading bacterium agent is a commercial VOCs degrading bacterium agent, and the cell density > .

[0034] The second filtration layer includes mixed aggregates, the particle size of the mixed aggregates is 2 to 4 mm, the mixed aggregates include diatomite aggregates and steel slag aggregates, the diatomite aggregates account for 60% of the weight of the mixed aggregates, and the steel slag aggregates account for 40% of the weight of the mixed aggregates.

[0035] S4. Set up an electrode array and use the electrode array to generate a voltage gradient. The voltage gradient is used to promote the migration of groundwater pollutants towards the multi-stage reaction wall.

[0036] In this embodiment, the electrode array includes at least three pairs of electrode groups, and the distance between adjacent two pairs of electrode groups is set to be 3 to 5 meters. Among them, each pair of electrode groups is respectively set as a positive electrode and a negative electrode, and the electrodes adjacent to each other are opposite electrodes.

[0037] A voltage gradient is generated by controlling the voltage amplitude and phase of the electrode groups, and an alternating electric field is generated by periodically switching the positive and negative electrodes of the electrode groups. In this way, under the action of the voltage gradient and the alternating electric field, groundwater pollutants are promoted to migrate towards the multi-stage reaction wall, thereby improving the remediation efficiency of groundwater.

[0038] It should be noted that the diatomite aggregate has a porous structure, and pollutants can be intercepted in the pores of the diatomite aggregate through physical adsorption. The steel slag aggregate contains alkaline components, which can adjust the pH value of groundwater to make the groundwater in a slightly alkaline environment. This slightly alkaline environment is conducive to the precipitation of pollutants. In this way, the first filtration layer can adsorb groundwater pollutants and achieve the remediation of groundwater.

[0039] The zero-valent iron-biochar composite microcapsule can reduce groundwater heavy metal ions to low-valent or zero-valent metals, making it easier for pollutants to form precipitates. The biochar has a porous structure and a large number of surface charges, which can maintain the reduction effect of zero-valent iron and enhance the remediation effect on pollutants through surface adsorption and other effects.

[0040] The microorganisms in the VOCs degrading bacterium agent can use VOCs as a carbon source and energy source for metabolism, and then decompose groundwater pollutants into harmless small molecule substances such as carbon dioxide and water.

[0041] In this way, using the multi-stage reaction wall to remediate groundwater can effectively remove different pollutants in groundwater, significantly improve the remediation efficiency, and ensure the remediation effect at the same time.

[0042] S5. Collect the reaction data of the multi-stage reaction wall, and perform remediation on the reaction media in the core reaction layer and the reaction media in the biological enhancement layer in the case of abnormal reaction data.

[0043] In this embodiment, the reaction data includes the oxidation-reduction potential and the dissolved oxygen concentration. During the process of collecting the reaction data of the multi-stage reaction wall, the oxidation-reduction potential is obtained, and the dissolved oxygen concentration is obtained. Among them, the oxidation-reduction potential is collected based on the oxidation-reduction 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.

[0044] Then, perform remediation on the reaction media in the core reaction layer and the reaction media in the biological enhancement layer according to the reaction data.

[0045] 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, a redox potential sensor is used to monitor the redox potential of the core reaction layer. When the reaction medium in the core reaction layer is about to be exhausted, the changing trend of the redox potential is different from the preset potential changing trend. At this time, the reaction data is abnormal. By setting an ultrasonic transmitter inside the core reaction layer and emitting ultrasonic waves with a preset ultrasonic frequency, the passivation layers such as iron hydroxide and iron oxide on the surface of the zero-valent iron microcapsules can be removed, exposing the zero-valent iron again, thereby realizing the repair of the reaction medium in the core reaction layer. The preset ultrasonic frequency can be 15 to 28 KHz.

[0046] For example, place an ultrasonic generator in the core reaction layer. When the changing trend of the redox potential is contrary to the preset potential changing trend, control the ultrasonic generator to emit ultrasonic waves with a frequency of 20 KHz to repair the reaction medium in the core reaction layer.

[0047] Furthermore, the degrading bacterium agent in the bioaugmentation layer is an aerobic bacterium and is relatively sensitive to the dissolved oxygen concentration. By using a dissolved oxygen sensor to collect the dissolved oxygen concentration in real time, it can be fed back whether the degrading bacterium agent needs aeration. An aeration device is arranged at the top of the bioaugmentation layer. When the dissolved oxygen concentration is less than the preset oxygen concentration threshold, oxygen is transported to the bottom of the bioaugmentation layer through the aeration device to increase the dissolved oxygen concentration in the bioaugmentation layer, thereby preventing the degrading bacterium agent from being inactivated due to lack of oxygen.

[0048] S22. If the concentration data is less than or equal to the preset concentration threshold, mark the polluted area as a low-concentration polluted area.

[0049] In this embodiment, if the polluted area is a low-concentration polluted area, there is no need to spray the reaction column group formed by the slow-release microspheres. A multi-stage reaction wall is arranged downstream of the groundwater pollution plume. The multi-stage reaction wall includes a first filter layer, a core reaction layer, a bioaugmentation layer, and a second filter layer stacked in sequence; an electrode array is set, and a voltage gradient is generated by using the electrode array. The voltage gradient is used to promote the migration of groundwater pollutants towards the multi-stage reaction wall, so that the multi-stage reaction wall adsorbs or removes heavy metals and organic substances in the groundwater pollutants; 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 bioaugmentation layer are repaired.

[0050] The above process has the same functions as steps S3, S4, and S5, and will not be elaborated here.

[0051] In this embodiment, based on the collected concentration data of groundwater pollutants, the pollutant removal rate is calculated, and when the reaction data is abnormal, an alarm prompt message is generated.

[0052] For example, the random forest algorithm is used to generate a material failure warning based on reaction data, and the material failure warning is used to prompt the failure of the reaction medium. Another example is using the non-dominated sorting genetic algorithm to calculate the addition amount of the reaction medium. Still another example is simulating the distribution of the groundwater flow field through a modular groundwater flow model.

[0053] 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 grasped, and intelligent alarms can be issued when the reaction medium fails in the multi-stage reaction wall, reducing the operation and maintenance costs.

[0054] As Figure 2 shown in the figure, an embodiment of the present invention further 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.

[0055] The data acquisition module 201 is configured to: collect the concentration data of groundwater pollutants in the polluted area, and collect the reaction data of the multi-stage reaction wall. The multi-stage reaction wall includes a first filtration layer, a core reaction layer, a bioaugmentation layer, and a second filtration layer stacked in sequence. The reaction data includes the redox potential of the core reaction layer and the dissolved oxygen concentration of the bioaugmentation layer.

[0056] The concentration response module 202 is configured to: if the concentration data is greater than a preset concentration threshold, mark the polluted area as a high-concentration polluted area and spray a reaction column group formed by slow-release microspheres into the high-concentration polluted 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 polluted area as a low-concentration polluted area.

[0057] The hydraulic regulation module 203 is configured to: generate a voltage gradient based on the electrode array to promote the migration of groundwater pollutants towards the multi-stage reaction wall 204.

[0058] The multi-stage reaction wall 204 is configured to: adsorb or remove heavy metals and organic matters in groundwater pollutants.

[0059] 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 bioaugmentation layer in the case of abnormal reaction data.

[0060] To make the technical solution of the present invention clearer, the implementation manner of the present invention will be described in detail below through a first embodiment of a groundwater remediation experimental device.

[0061] In the laboratory, a groundwater environment polluted by heavy metals (hexavalent chromium) and organic pollutants (1,2-dichloroethane) is simulated. An experimental device is used to simulate the construction of a groundwater remediation system based on a multi-stage reaction wall. AsFigure 3 and Figure 4 As shown, first, select a geological body box with a length of 50 cm, a width of 20 cm, and a height of 20 cm, and fill the geological body box with a structure compacted by clay. Construct a low-permeability geological body 12 and a relatively water-resistant geological body 13. The thickness ratio of the low-permeability geological body 12 to the relatively water-resistant 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.

[0062] Then, prepare the first simulated groundwater sample, inject a water sample with an average concentration of 20 mg / L of hexavalent chromium and an average concentration of 30 mg / L of 1,2-dichloroethane into the simulated formation, cure for 7 days, and do not apply a water flow gradient during the curing process to ensure the spread of the pollution plume, thereby forming a low-concentration pollution area.

[0063] Set a water replenishment connection hole at the connection between the low-permeability geological body 12 and the upstream water source, with a pore diameter of 5 mm, and set a filter screen to prevent soil loss.

[0064] Set the water level line upstream of the device below the low-permeability geological body 12, and the area above the upstream water level line is the groundwater upstream replenishment area 14. Control the downstream water level line to be 1 cm lower than the upstream through a peristaltic pump 16, thereby maintaining the hydraulic gradient. The area above the downstream water level line is the groundwater downstream catchment area 15.

[0065] Then, construct a multi-stage reaction wall. The multi-stage reaction wall is a permeable reaction wall, which consists of four structural layers. From the upstream to the downstream direction of the water flow, they are the surface filtration layer 1 (i.e., the first filtration layer), the core reaction layer 2, the bioaugmentation layer 3, and the surface filtration layer 1 (i.e., the second filtration layer). Among them, the surface filtration layer 1 is filled with 60 wt% diatomite / steel slag aggregate, the aggregate has a particle size of 3 mm, and the first filtration layer is 2 cm thick. The core reaction layer 2 is filled with zero-valent iron microcapsules, specifically Fe 0 @BC microcapsules. Among them, the iron-carbon mass ratio of the Fe 0 @BC microcapsules is 1:3, and it is coated with a 50 µm thick sodium alginate membrane. The thickness of the core reaction layer 2 is 2 cm. The bioaugmentation layer 3 is filled with a commercial VOCs degrading bacterium agent immobilized and embedded by an agar-activated carbon microporous structure, and the cell density > , and the thickness of the bioaugmentation layer 3 is 2 cm. The filler and thickness of the second filtration layer are the same as those of the first filtration layer.

[0066] Set an ultrasonic generator 10 and an ORP sensor 8 (i.e., an oxidation-reduction potential sensor) in the core reaction layer 2, and cross-deploy a DO sensor 9 (i.e., a dissolved oxygen sensor) and an aeration device 11 in the bioaugmentation layer 3. Among them, the number of ORP sensors 8 is 3, and the interval between two adjacent ORP sensors 8 is 5 cm. The number of DO sensors 9 is 3, and the interval between two adjacent DO sensors 9 is 5 cm.

[0067] Five groups of electrode arrays 4 are set at an interval of 4 cm to form a voltage gradient of 0.8 V / cm. The migration and enrichment of pollutants are promoted through an alternating electric field (frequency 1 Hz, voltage 1 V). The migration rate of pollutants is 0.8 m / d. The redox potential and dissolved oxygen concentration during the simulated operation process are collected in real time.

[0068] When the redox potential rises to the 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.

[0069] After the simulated experimental device has been running for 30 days, an appropriate amount of water sample is taken from the pollution source area. The concentration of hexavalent chromium in the water sample drops below 1.1 mg / L, and the concentration of 1,2-dichloroethane drops below 2.3 mg / L. From this, the heavy metal removal rate is calculated to be over 94%, and the VOCs degradation rate is over 92%. Hexavalent chromium and 1,2-dichloroethane are not detected in the surface filter layer of the downstream barrier wall. It can be seen that for the remediation of groundwater in low-concentration areas, the method of using a multi-stage reaction wall to adsorb or remove groundwater pollutants can achieve the remediation of groundwater, and the remediation effect is remarkable.

[0070] In the second embodiment of the groundwater remediation experimental device, the configuration method of the first simulated groundwater sample is modified to configure the second simulated groundwater sample, and the simulation process of the rest of the experimental device remains unchanged. During the process of configuring the second simulated groundwater sample, a water sample with an average concentration of 50 mg / L of hexavalent chromium and an average concentration of 100 mg / L of 1,2-dichloroethane is injected into the simulated formation and cured for 7 days. During the curing process, no water flow gradient is applied to ensure the diffusion of the pollution plume, thereby forming a high-concentration pollution area 6.

[0071] Then, persulfate slow-release microspheres are arranged in the high-concentration pollution area 6 by injection to form a reaction column group 5. The particle size of the persulfate slow-release microspheres is 100 µm, the diameter of the reaction column group 5 is 1.5 cm, and a total of 2 horizontally arranged reaction column groups 5 are set. A small container is used to simulate the pH regulation well 7, and CaO slow-release material is placed in the pH regulation well 7.

[0072] After the simulated system has been running for 30 days, an appropriate amount of water sample is taken from the pollution source area. The concentration of hexavalent chromium in the water sample drops below 5 mg / L, and the concentration of 1,2-dichloroethane drops below 3.5 mg / L. It can be calculated that the removal rate of heavy metal chromium is over 90%, and the VOCs degradation rate is over 96%. Hexavalent chromium and 1,2-dichloroethane are not detected in the surface filter layer of the downstream barrier wall. It can be seen that for the groundwater remediation method in high-concentration areas, the method of first using a reaction column group to adsorb or remove groundwater pollutants and then using a multi-stage reaction wall to adsorb or remove groundwater pollutants can achieve a good groundwater remediation effect.

[0073] As can be seen from the above technical solutions, 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 remediated by combining the injection of slow-release microspheres and a 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 remediate the groundwater, thereby achieving targeted remediation of different polluted areas. And by using the electro-migration enrichment effect, the groundwater pollutants are guided to migrate directionally to the multi-stage reaction wall, and the migration rate of the groundwater pollutants is increased, thereby improving the remediation effect. And it is judged whether it is necessary to repair the reaction medium in the multi-stage reaction wall according to the reaction data of the multi-stage reaction wall, thereby prolonging the service life of the reaction medium, reducing the replacement frequency, and lowering the operation and maintenance costs.

[0074] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A groundwater remediation method based on a multi-stage reaction wall, characterized in that, Including: Collecting the concentration data of groundwater pollutants in the contaminated area; If the concentration data is greater than a preset concentration threshold, marking the contaminated area as a high-concentration contaminated area, and injecting a reaction column group formed by slow-release microspheres into the high-concentration contaminated area, where the slow-release microspheres are used to adsorb or remove the groundwater pollutants; Setting up a multi-stage reaction wall downstream of the groundwater pollution plume, where the multi-stage reaction wall includes a first filter layer, a core reaction layer, a bioaugmentation layer, and a second filter layer stacked in sequence; Setting up an electrode array and using the electrode array to generate a voltage gradient, where the voltage gradient is used to promote the migration of the groundwater pollutants towards the multi-stage reaction wall, so that the multi-stage reaction wall adsorbs or removes heavy metals and organic matters in the groundwater pollutants; Collecting the reaction data of the multi-stage reaction wall, and performing repair on the reaction media in the core reaction layer and the reaction media in the bioaugmentation layer when the reaction data is abnormal.

2. The groundwater remediation method according to claim 1, characterized in that, Also including: If the concentration data is less than or equal to the preset concentration threshold, marking the contaminated area as a low-concentration contaminated area; Setting up a multi-stage reaction wall downstream of the groundwater pollution plume, where the multi-stage reaction wall includes a first filter layer, a core reaction layer, a bioaugmentation layer, and a second filter layer stacked in sequence; Setting up an electrode array and using the electrode array to generate a voltage gradient, where the voltage gradient is used to promote the migration of the groundwater pollutants towards the multi-stage reaction wall, so that the multi-stage reaction wall adsorbs or removes heavy metals and organic matters in the groundwater pollutants; Collecting the reaction data of the multi-stage reaction wall, and performing repair on the reaction media in the core reaction layer and the reaction media in the bioaugmentation layer when the reaction data is abnormal.

3. The groundwater remediation method according to claim 1, characterized in that, Before injecting the reaction column group formed by slow-release microspheres into the high-concentration contaminated area, it also includes: Setting up a regulating device in the high-concentration contaminated area, where the regulating device is used to regulate the pH value of the high-concentration contaminated area; The regulating device is internally provided with a slow-release material, and the slow-release material includes at least one of calcium oxide and sodium bicarbonate.

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

5. The groundwater remediation method according to claim 1, wherein The first filter layer includes mixed aggregates, the particle size of the mixed aggregates is 2 to 4 mm, the mixed aggregates include diatomite aggregates and steel slag aggregates, the diatomite aggregates account for 60% of the weight of the mixed aggregates, and the steel slag aggregates account for 40% of the weight of the mixed aggregates; The core reaction layer includes zero-valent iron-biochar composite microcapsules, and the outside of the zero-valent iron-biochar composite microcapsules is wrapped with a preset thickness of sodium alginate film. The zero-valent iron-biochar composite microcapsules are used to adsorb or reduce heavy metals in the groundwater pollutants. The bioaugmentation layer includes a degradation bacterium agent, which is fixed based on the microporous structures of agar and activated carbon, and is used for decomposing the organic matters in the groundwater pollutants; The second filtration layer includes the mixed aggregate, the particle size of the mixed aggregate is 2 to 4 mm, the mixed aggregate includes diatomite aggregate and steel slag aggregate, the diatomite 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.

6. The groundwater remediation method according to claim 1, wherein The acquisition of the reaction data of the multi-stage reaction wall includes: Obtaining the oxidation-reduction potential, which is collected based on the oxidation-reduction potential sensor in the core reaction layer; Obtaining the dissolved oxygen concentration, which is collected based on the dissolved oxygen sensor in the bioaugmentation layer.

7. The groundwater remediation method according to claim 6, wherein, In the case of abnormal reaction data, the repair of the reaction medium in the core reaction layer and the reaction medium in the bioaugmentation layer includes: In the case where the change trend of the oxidation-reduction potential is different from the preset potential change trend, ultrasonic waves with a preset ultrasonic frequency are emitted to the core reaction layer, the ultrasonic waves are emitted by an ultrasonic generator, and the ultrasonic generator is arranged inside the core reaction layer; In the case where the dissolved oxygen concentration is less than the preset oxygen concentration threshold, oxygen is supplied to the bioaugmentation layer, and the oxygen is supplied by an aeration device, and the aeration device is arranged at the top of the bioaugmentation layer.

8. The groundwater remediation method according to claim 1, wherein, The setting of the electrode array and the generation of the voltage gradient by using the electrode array include: Setting at least three pairs of electrode groups, the distance between adjacent two pairs of the electrode groups is 3 to 5 m, each pair of the electrode groups is respectively set as a positive electrode and a negative electrode, and the adjacent electrodes are opposite electrodes; 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, and the voltage gradient and the alternating electric field are used to increase the migration rate of the groundwater pollutants.

9. The groundwater remediation method according to claim 1, characterized in that, It further includes: Calculating the removal rate of the groundwater pollutants based on the collected concentration data of the groundwater pollutants; Generating an alarm prompt message in the case of abnormal reaction data.

10. A groundwater remediation system based on a multi-stage reaction wall, characterized in that, It includes: A data acquisition module, configured to: collect the concentration data of the groundwater pollutants in the polluted area, and collect the reaction data of the multi-stage reaction wall, the multi-stage reaction wall includes a first filtration layer, a core reaction layer, a bioaugmentation layer and a second filtration layer stacked in sequence, and the reaction data includes the oxidation-reduction potential of the core reaction layer and the dissolved oxygen concentration of the bioaugmentation layer; A concentration response module, configured to: if the concentration data is greater than the preset concentration threshold, mark the polluted area as a high-concentration polluted area, and inject a reaction column group formed by slow-release microspheres into the high-concentration polluted area, and the slow-release microspheres are used for adsorbing or removing the groundwater pollutants; And, if the concentration data is less than or equal to the preset concentration threshold, mark the polluted area as a low-concentration polluted area; A hydraulic regulation module, configured to: generate a voltage gradient based on the electrode array to promote the migration of the groundwater pollutants to the multi-stage reaction wall; The multi-stage reaction wall is configured to adsorb or remove heavy metals and organic substances in the groundwater pollutants; The operation and maintenance control module is configured to perform repair on the reaction medium in the core reaction layer and the reaction medium in the biological enhancement layer in the case of abnormal reaction data.

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