Method and system for in-situ chemical reduction remediation of halogenated hydrocarbon contaminated groundwater by electrochemical enhancement

Abstract

The application discloses a method and system for electrochemical strengthening in-situ chemical reduction remediation of halogenated hydrocarbon contaminated groundwater. The method is to compound zero-valent iron, activated carbon and biologically available organic carbon source, add an additive to prepare a dilute slurry with water, and form a reaction zone in the contaminated aquifer by direct injection; electrode wells are arranged in the vicinity of the reaction zone and a low-voltage weak electric field is applied, wherein the negative electrode is closer to the reaction zone than the positive electrode, so as to promote the directional transmission of electrons and the recovery of the surface reactivity of zero-valent iron; at the same time, water pumping and reinjection are started to form a hydraulic cycle, so that the contaminated groundwater repeatedly flows through the reaction zone. The method can quickly reduce the redox potential of the groundwater to-200 mV to-300 mV, and enriches Trichlorobacter, Sulfurospirillum and other organic halogen respiration electric active bacteria. The pilot test results show that the method has a significant removal effect on pollutants such as dichloromethane, chloroform, dichloroethane, chloroethylene and trichlorobenzene.

Description

Technical Field

[0001] This invention belongs to the field of in-situ remediation technology for groundwater pollution, specifically relating to a method and system for electrochemically enhanced in-situ chemical reduction remediation of groundwater contaminated with halogenated hydrocarbons by synergistic application of in-situ chemical reduction, weak electric field electrochemical enhancement, and groundwater hydraulic circulation. Background Technology

[0002] Groundwater contaminated with halogenated hydrocarbons is typically characterized by a complex array of pollutants, high mobility, high toxicity, and long remediation periods. Common target pollutants include chloromethane, chloroethane, chloroethylene, chlorobenzene, and their polychlorinated homologues. In-situ chemical reduction technology, which involves injecting reducing materials into the aquifer to reduce and dechlorinate the pollutants or convert them into less toxic products, is an important technical approach for remediating halogenated hydrocarbon-contaminated groundwater.

[0003] However, in low-permeability clay strata or complex contaminated sites, traditional reagent injection is easily limited by slurry viscosity, injection radius, and groundwater flow conditions, resulting in a limited range of influence in the reaction zone. Zero-valent iron materials may also experience surface passivation during operation, leading to a decrease in continuous electron supply capacity. Relying solely on chemical reduction may also be insufficient to quickly establish a stable, strongly reducing environment, thus failing to adequately promote the enrichment of electroactive dechlorination microorganisms.

[0004] There are reports of using electrodynamics or weak electric fields to assist in the remediation of contaminated groundwater in existing technologies, but these usually rely on electromigration or electroosmosis as the main mechanism, with high electric field power, and are not applied in conjunction with in-situ chemical reducing agents and hydraulic circulation to remediate complex halogenated hydrocarbon pollution in low-permeability formations.

[0005] Therefore, there is a need for an in-situ groundwater remediation method that can simultaneously improve agent distribution, restore or maintain zero-valent iron reactivity, promote electron transfer, and activate indigenous functional microorganisms, in order to improve the remediation efficiency and long-term stability of groundwater contaminated with complex halogenated hydrocarbons. Summary of the Invention

[0006] This invention aims to solve the following problems: compound reducing agents are difficult to uniformly construct reaction zones in low-permeability formations; the electron-donating capacity of zero-valent iron decreases with surface passivation; a single ISCR system is difficult to quickly establish a strong reducing environment; and the remediation efficiency is insufficient when complex halogenated hydrocarbons, especially chlorinated alkanes, chlorinated alkenes and high-chlorinated aromatic hydrocarbons coexist.

[0007] Technical solution

[0008] To address the aforementioned problems, this invention provides an electrochemically enhanced in-situ chemical reduction method for the remediation of groundwater contaminated with halocarbons. The method involves first preparing a compound reducing agent containing zero-valent iron, activated carbon, and an organic carbon source, and then mixing it with water to form an injectable dilute mud slurry. This slurry is then directly injected into the contaminated aquifer to form a reaction zone. Electrode wells are installed in the vicinity of the reaction zone, and a low-voltage, weak electric field is applied. Simultaneously, groundwater hydraulic circulation is established through pumping and reinjection, allowing the contaminated groundwater to repeatedly pass through the reaction zone.

[0009] Zero-valent iron provides electron donors for chemical reduction, activated carbon provides the adsorption and microbial attachment interface, bioavailable carbon sources such as wheat bran promote the growth of anaerobic and organohalogen respiration microorganisms, and additives such as guar gum improve slurry stability and injectability. A low-voltage, weak electric field promotes electron transfer in the formation medium, lowers the system's redox potential, and helps restore the surface reactivity of zero-valent iron. Hydraulic circulation increases the frequency of contact between groundwater and the reaction zone, expanding the influence range of the reagents and the reducing environment.

[0010] The method specifically includes the following steps:

[0011] A non-water-soluble reducing remediation material, which is a compound of zero-valent iron, activated carbon, and bioavailable organic carbon sources, is mixed with water to prepare a dilute mud injection medium.

[0012] The injection medium is injected into the contaminated aquifer by direct injection to form an in-situ chemical reduction reaction zone;

[0013] Electrode wells are installed in the vicinity of the reaction zone and a low-voltage weak electric field is applied to promote the directional transfer of electrons to the reaction zone and reduce the redox potential of groundwater.

[0014] A hydraulic circulation system of pumping and reinjection is established between the upstream and downstream of the contaminated groundwater, allowing the contaminated groundwater to flow through the reaction zone.

[0015] The redox potential, dissolved oxygen, pH, conductivity, concentration of halogenated hydrocarbons, and concentration of dechlorination products in groundwater are monitored. Based on the monitoring results, the operating parameters of injection, hydraulic circulation, and weak electric field are controlled to maintain a strong reducing environment in the target remediation area and to continuously reduce and dechlorinate halogenated hydrocarbons.

[0016] Preferably, the compound in-situ chemical reducing material includes zero-valent iron, activated carbon, wheat bran and thickening agent, wherein the mass ratio of zero-valent iron, activated carbon and wheat bran is (0.5-2):(0.5-2):(0.5-2), and the thickening agent accounts for 1%-5% of the total mass of the compound in-situ chemical reducing material.

[0017] Preferably, the mass ratio of zero-valent iron, activated carbon, and wheat bran is 1:1:1, and the three together account for 95%-99% of the total mass of the compound in-situ chemical reducing agent. The thickening agent is guar gum and accounts for 2% of the total mass.

[0018] Preferably, the mass concentration of the diluted mud injection medium is 20%-35%, the dosage of the compound in-situ chemical reducing material is 0.3%-2.0% of the soil mass of the target remediation area, and the total injection volume of the injection medium is 20%-80% of the effective pore volume of the target remediation area.

[0019] Preferably, the direct injection employs two rows of staggered injection points to form a reaction zone. The injection line formed by these injection points is arranged transversely to the groundwater flow direction. The injection depth of each injection point penetrates the contaminated groundwater aquifer. The injection pressure is 2.5-7.5 MPa, and the output flow rate is 4-40 m³ / s. 3 / h.

[0020] Preferably, the electrode well includes a negative electrode well and a positive electrode well, with the negative electrode well being closer to the in-situ chemical reduction reaction zone than the positive electrode well; the current is controlled at 0.5-3.0A during the operation of the low-voltage weak electric field, and the operating power of a single device does not exceed 50W; under the action of the low-voltage weak electric field, electrons are directionally transferred from the positive electrode well to the negative electrode well and migrate towards the reaction zone.

[0021] Preferably, the hydraulic circulation is achieved through an upstream reinjection well and a downstream pumping well, controlling the hydraulic residence time of groundwater in the reaction zone to be 15-45 days.

[0022] Preferably, the method reduces the redox potential of groundwater in the target remediation area to -200mV to -300mV; the halogenated hydrocarbons include one or more of dichloromethane, trichloromethane, dichloroethane, vinyl chloride, and trichlorobenzene; the low-voltage weak electric field promotes the enrichment of electroactive organic halogenated respiratory bacteria, including one or more of Trichlorobacter, Sulfurospirillum, and Desulfobulbus.

[0023] The present invention also provides an electrochemically enhanced in-situ chemical reduction remediation system for implementing the method, comprising:

[0024] The compound preparation unit is used to prepare a dilute mud injection medium containing zero-valent iron, activated carbon, and bioavailable organic carbon sources.

[0025] The direct injection unit has its injection end inserted into the contaminated aquifer to form an in-situ chemical reduction reaction zone within the aquifer.

[0026] The electrode enhancement unit includes positive electrode wells and negative electrode wells arranged on both sides of the reaction zone. The negative electrode wells are closer to the reaction zone than the positive electrode wells. The screen tube section of the electrode wells runs through the entire depth of the polluted aquifer. The electrode wells are connected to a low-voltage DC power supply via cables.

[0027] The hydraulic circulation unit includes a reinjection well located upstream of the reaction zone and a pumping well located downstream. The outlet of the pumping well is connected to the inlet of the reinjection well via a pipeline to form a closed hydraulic circulation loop.

[0028] The monitoring unit includes at least one monitoring well located at the center of the reaction zone, and the monitoring well is equipped with a sensor for acquiring groundwater quality and operating parameters;

[0029] The control unit is connected to the direct injection unit, electrode strengthening unit, hydraulic circulation unit and monitoring unit respectively, and is used to dynamically adjust the operating parameters of each unit according to the monitoring results.

[0030] Furthermore, the direct-push injection unit is an integrated direct-push drilling-injection equipment that combines direct-push drilling, hydraulic fracturing, pneumatic fracturing, and atomized injection functions.

[0031] Beneficial effects

[0032] It can construct a continuous reaction zone within low-permeability aquifers, thereby improving the contact efficiency between compound reagents and contaminated groundwater;

[0033] It can rapidly reduce the oxidation-reduction potential of groundwater to a level conducive to reduction and dechlorination, preferably reaching -200mV to -300mV;

[0034] It can promote the enrichment of electroactive organic halogenated respiratory bacteria such as Trichlorobacter, Sulfurospirillum, and Desulfobulbus, and improve the long-term dechlorination potential of the system;

[0035] It can process multiple types of halogenated hydrocarbons simultaneously, and has good applicability to chloroalkanes, chloroolefins and trichlorobenzene;

[0036] The low power consumption of the weak electric field makes it suitable for integration with on-site in-situ injection and hydraulic circulation facilities. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the plan layout of the electrochemically enhanced in-situ chemical reduction remediation system of the present invention. In the diagram: 1-Target remediation zone; 2-In-situ chemical reduction reaction zone; 3-Double-row staggered direct injection points; 4-Positive electrode well; 5-Negative electrode well; 6-Upstream reinjection well; 7-Midstream monitoring well; 8-Downstream pumping well. The injection points form an injection row arranged transversely to the groundwater flow direction. The negative electrode well is closer to the reaction zone than the positive electrode well, and a groundwater hydraulic cycle is formed between the upstream reinjection well and the downstream pumping well.

[0038] Figure 2This is a schematic diagram of the double-row staggered injection point layout within the reaction zone. In the diagram: 3 - Double-row staggered direct-push injection point; within the projection range of the reaction zone, the two rows of injection points are staggered and basically perpendicular to the groundwater flow direction, so that the polluted groundwater must flow through the reagent reaction zone.

[0039] Figure 3 This is a schematic diagram of the electrode well and hydraulic circulation profile. In the diagram: 4 - positive electrode well; 5 - negative electrode well; 6 - upstream reinjection well; 7 - midstream monitoring well; 8 - downstream pumping well. The screen section of the electrode well runs through the entire depth of the contaminated aquifer. A closed hydraulic circulation loop is formed between the pumping well and the reinjection well. Under the action of a low-pressure, weak electric field, electrons are directionally transferred from the positive electrode well to the negative electrode well.

[0040] Figure 4 This is a flow chart of the electrochemically enhanced in-situ chemical reduction remediation process of the present invention. In the figure: S1 Site survey to delineate the target area; S2 Preparation of slurry by compounding reagents; S3 Direct injection to form a reaction zone; S4 Deploying electrodes to apply a weak electric field; S5 Pumping and reinjecting water for hydraulic circulation; S6 Monitoring water quality and microbial community; S7 Adjusting operation for continuous remediation. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the implementation of the present invention is not limited thereto.

[0042] 1. Setting up the target repair area and reaction zone

[0043] like Figure 1 As shown, in a groundwater contaminated site with halogenated hydrocarbons as the main target pollutant, a target remediation zone 1 was selected, measuring approximately 10m in length, 5m in width, and 1m to 10m below ground level. Based on the groundwater flow direction, monitoring wells 7 were installed at the center, upstream, and downstream of the injection area; the upstream and downstream wells also served as reinjection wells 6 and pumping wells 8, respectively, to construct a hydraulic circulation system.

[0044] like Figure 2 As shown, reaction zone 2 is formed by two rows of staggered direct-injection points 3, with the injection rows arranged transversely to the groundwater flow direction. The injection depth of each injection point penetrates the target contaminated aquifer. This arrangement can reduce injection blind spots and improve the lateral continuity of the reaction zone.

[0045] 2. Compound reducing raw materials and injection

[0046] The compound raw materials consist of zero-valent iron, activated carbon, wheat bran, and guar gum. Zero-valent iron, activated carbon, and wheat bran are compounded in a 1:1:1 mass ratio, with a total mass ratio of approximately 98%, and guar gum accounts for approximately 2%. The zero-valent iron is preferably powdered with an iron content greater than 90%; the activated carbon is preferably wood-based powdered activated carbon; wheat bran serves as a slow-release organic carbon source; and guar gum acts as a thickener and suspension stabilizer.

[0047] The compound reducing agent is mixed with water to prepare a diluted slurry with a mass concentration of 20%-35%, preferably 27%-30%, for immediate use. The dosage of the agent is determined based on an addition ratio of approximately 1% of the soil mass in the target remediation area, and the injection volume is determined based on approximately 50% of the effective pore volume of the target remediation area. During injection, the injection pressure and flow rate are dynamically adjusted according to the formation's acceptability, equipment pressure, and slurry leakage. In one embodiment, the output pressure is 2.5-7.5 MPa, and the output flow rate is 4-40 m³ / h. 3 / h.

[0048] 3. Weak electric field enhancement and hydraulic circulation

[0049] like Figure 1 As shown, electrode wells are arranged in the vicinity of reaction zone 2: positive electrode well 4 is arranged on the left side of the reaction zone, and negative electrode well 5 is arranged on the right side of the reaction zone, with the negative electrode well being closer to the reaction zone than the positive electrode well. Figure 3 As shown, the screen section of the electrode well extends through the entire depth of the contaminated aquifer, ensuring that the weak electric field covers the entire contaminated area. The electrode well depth is preferably approximately 10.5m below the ground surface, with the well screen located 1.5m to 10m below the ground surface. The electrode can be spirally wound around a PVC support pipe, and the connecting lines are protected by PVC conduits and laid in situ.

[0050] After injection and electrode installation, the voltage was adjusted to bring the current to approximately 1.5A and maintained. Voltage and current were monitored daily during operation. Power was temporarily shut off during groundwater sample collection and restored after sampling. This weak electric field does not primarily function through electromigration; instead, it induces redox reactions at the interface between media particles and pore water, and promotes the directional transfer of electrons from the positive electrode well to the negative electrode well (e.g., ...). Figure 3 (As indicated by the electron transfer arrow), it promotes the recovery of surface reactivity of zero-valent iron and maintains a low redox potential.

[0051] like Figure 3 As shown, the hydraulic circulation unit includes a reinjection well 6 located upstream of the reaction zone and a pumping well 8 located downstream. The outlet of the pumping well is connected to the inlet of the reinjection well via a pipeline, forming a closed hydraulic circulation loop. After the injection construction is completed, pumping and reinjection are started to control the hydraulic residence time of groundwater in the reaction zone to approximately one month. Depending on the site's water receiving capacity, the circulation flow rate can be adjusted from several hundred mL / min to approximately 1.5 m³ / min. 3 Within a range of / d, to maintain pumping-injection balance and promote repeated passage of contaminated groundwater through the reaction zone.

[0052] 4. Monitoring and parameter control

[0053] like Figure 4 As shown in the flowchart, the method of the present invention is executed sequentially according to the following steps:

[0054] S1 Site Investigation and Target Area Delineation: Conduct site hydrogeological investigation and pollution characteristic identification to determine the scope and depth of the target remediation area.

[0055] S2 compound reagent preparation slurry: compounded according to the mass ratio of zero-valent iron: activated carbon: wheat bran = 1:1:1, with about 2% guar gum as an adjuvant, and mixed with water to prepare an injectable thin mud slurry with a mass concentration of 27%-30%.

[0056] S3 Direct injection to form a reaction zone: Using high-pressure direct injection at 2.5-7.5MPa, the agent is injected into the aquifer at a dosage ratio of about 1% of the target area soil mass to form a continuous reduction reaction zone that cuts across the water flow.

[0057] S4. Apply a weak electric field by arranging electrodes: Install positive and negative electrode wells, apply a low-voltage weak electric field and control the current to 0.5-3.0A (preferably 1.5A) to promote electron transfer and the formation of a strong reducing environment.

[0058] S5 Pumping and Reinjection Hydraulic Circulation: Starts downstream pumping and upstream reinjection, controlling the hydraulic residence time of groundwater in the reaction zone to about 1 month, prompting the polluted groundwater to repeatedly flow through the reaction zone.

[0059] S6 monitors water quality microbial communities: continuously monitors groundwater level, pH, dissolved oxygen, redox potential, conductivity, total organic carbon, ferrous iron, total iron, chloride ions, nitrate, sulfate, total bacterial count, target halogenated hydrocarbons, and typical dechlorination intermediates; groundwater samples can be collected before operation, on day 33 and day 64 of operation, and microbial community changes can be analyzed based on 16S rRNA gene sequencing, with a focus on monitoring the enrichment of electroactive organic halogenated respiratory bacteria such as Trichlorobacter, Sulfurospirillum, and Desulfobulbus.

[0060] S7 Regulated Operation Continuous Repair: Based on monitoring results, the injection parameters, electric field strength, and hydraulic circulation flow rate are dynamically adjusted to maintain a strong reducing environment of -200mV to -300mV, and the repair continues until the pollutants meet the standards.

[0061] 5. Pilot-scale results

[0062] Pilot-scale results showed that the carbon and iron sources in the compound reducing agents increased the TOC, Fe2+, total iron, and Cl- content in groundwater, creating a reducing environment. Compared with ISCR alone, electrochemically enhanced ISCR could establish a strong reducing environment more quickly, with groundwater ORP maintained in the range of -200mV to -300mV and methane concentration increased to approximately 10mg / L, indicating that a strong reducing environment for methanogenesis was established rapidly.

[0063] Regarding pollutants, electrochemically enhanced ISCR showed significant removal effects on low concentrations of dichloromethane, trichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,2-dichloropropane, and vinyl chloride, with some pollutants reaching undetectable levels by day 92. It also showed high removal rates for 1,2,3-trichlorobenzene and 1,2,4-trichlorobenzene. Microbiological results showed that electrochemical enhancement promoted the enrichment of electroactive or organohalogen-respiratory bacteria such as *Trichlorobacter*, *Sulfurospirillum*, and *Desulfobulbus*, indicating a synergistic effect between the weak electric field and the compound reducing agents.

[0064]

[0065] 6. Electrochemically Enhanced In-situ Chemical Reduction and Repair System

[0066] An electrochemically enhanced in-situ chemical reduction remediation system for implementing the above methods, such as Figure 1 and Figure 3 As shown, it includes:

[0067] Compound drug preparation unit: used to prepare dilute mud injection medium containing zero-valent iron, activated carbon and wheat bran;

[0068] Direct-push injection unit: Its injection end extends into the contaminated aquifer to form an in-situ chemical reduction reaction zone within the aquifer; the direct-push injection unit is preferably an integrated direct-push drilling-injection equipment that integrates direct-push drilling, hydraulic fracturing, pneumatic fracturing and atomized jetting functions.

[0069] Electrode enhancement unit: includes positive electrode well 4 and negative electrode well 5 arranged on both sides of the reaction zone. The negative electrode well is closer to the reaction zone than the positive electrode well. The screen tube section of the electrode well runs through the entire depth of the polluted aquifer. The electrode well is connected to a low-voltage DC power supply via cable.

[0070] Hydraulic circulation unit: includes a reinjection well 6 located upstream of the reaction zone and a pumping well 8 located downstream. The outlet of the pumping well is connected to the inlet of the reinjection well through a pipeline to form a closed hydraulic circulation loop.

[0071] Monitoring unit: includes at least one monitoring well 7 located at the center of the reaction zone, and sensors are installed in the monitoring well to acquire groundwater quality and operating parameters;

[0072] Control unit: Connected to the direct injection unit, electrode enhancement unit, hydraulic circulation unit and monitoring unit respectively, and used to dynamically adjust the operating parameters of each unit according to the monitoring results.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for electrochemically enhanced in-situ chemical reduction remediation of groundwater contaminated with halohydrocarbons, characterized in that, Includes the following steps: A non-water-soluble reducing remediation material, which is a compound of zero-valent iron, activated carbon, and bioavailable organic carbon sources, is mixed with water to prepare a dilute mud injection medium. The injection medium is injected into the contaminated aquifer by direct injection to form an in-situ chemical reduction reaction zone; Electrode wells are installed in the vicinity of the reaction zone and a low-voltage weak electric field is applied to promote the directional transfer of electrons to the reaction zone and reduce the redox potential of groundwater. A hydraulic circulation system of pumping and reinjection is established between the upstream and downstream of the contaminated groundwater, allowing the contaminated groundwater to flow through the reaction zone. The redox potential, dissolved oxygen, pH, conductivity, concentration of halogenated hydrocarbons, and concentration of dechlorination products in groundwater are monitored. Based on the monitoring results, the operating parameters of injection, hydraulic circulation, and weak electric field are controlled to maintain a strong reducing environment in the target remediation area and to continuously reduce and dechlorinate halogenated hydrocarbons.

2. The method according to claim 1, characterized in that, The compound in-situ chemical reducing material includes zero-valent iron, activated carbon, wheat bran and thickening agent, wherein the mass ratio of zero-valent iron, activated carbon and wheat bran is (0.5-2):(0.5-2):(0.5-2), and the thickening agent accounts for 1%-5% of the total mass of the compound in-situ chemical reducing material.

3. The method according to claim 2, characterized in that, The mass ratio of zero-valent iron, activated carbon, and wheat bran is 1:1:1, and the three together account for 95%-99% of the total mass of the compound in-situ chemical reducing materials. The thickening agent is guar gum and accounts for 2% of the total mass.

4. The method according to claim 1, characterized in that, The mass concentration of the diluted mud injection medium is 20%-35%, the dosage of the compound in-situ chemical reducing material is 0.3%-2.0% of the soil mass of the target remediation area, and the total injection volume of the injection medium is 20%-80% of the effective pore volume of the target remediation area.

5. The method according to claim 1, characterized in that, The direct injection employs two rows of staggered injection points to form a reaction zone. The injection column formed by these points is arranged transversely to the groundwater flow direction. The injection depth of each point penetrates the contaminated groundwater aquifer. The injection pressure is 2.5-7.5 MPa, and the output flow rate is 4-40 m³ / h. 3 / h.

6. The method according to claim 1, characterized in that, The electrode wells include negative electrode wells and positive electrode wells, with the negative electrode wells being closer to the in-situ chemical reduction reaction zone than the positive electrode wells. During operation of the low-voltage weak electric field, the current is controlled between 0.5-3.0A, and the operating power of a single device does not exceed 50W. Under the action of the low-voltage weak electric field, electrons are directionally transferred from the positive electrode well to the negative electrode well and migrate towards the reaction zone.

7. The method according to claim 1, characterized in that, The hydraulic circulation is achieved through upstream reinjection wells and downstream pumping wells, controlling the hydraulic residence time of groundwater in the reaction zone to be 15-45 days.

8. The method according to claim 1, characterized in that, The method reduces the redox potential of groundwater in the target remediation area to -200mV to -300mV; the halogenated hydrocarbons include one or more of dichloromethane, trichloromethane, dichloroethane, vinyl chloride, and trichlorobenzene; the low-voltage weak electric field promotes the enrichment of electroactive organic halogenated respiratory bacteria, including one or more of Trichlorobacter, Sulfurospirillum, and Desulfobulbus.

9. An electrochemically enhanced in-situ chemical reduction remediation system for implementing the method according to any one of claims 1-8, characterized in that, include: The compound preparation unit is used to prepare a dilute mud injection medium containing zero-valent iron, activated carbon, and bioavailable organic carbon sources. The direct injection unit has its injection end inserted into the contaminated aquifer to form an in-situ chemical reduction reaction zone within the aquifer. The electrode enhancement unit includes positive electrode wells and negative electrode wells arranged on both sides of the reaction zone. The negative electrode wells are closer to the reaction zone than the positive electrode wells. The screen tube section of the electrode wells runs through the entire depth of the polluted aquifer. The electrode wells are connected to a low-voltage DC power supply via cables. The hydraulic circulation unit includes a reinjection well located upstream of the reaction zone and a pumping well located downstream. The outlet of the pumping well is connected to the inlet of the reinjection well via a pipeline to form a closed hydraulic circulation loop. The monitoring unit includes at least one monitoring well located at the center of the reaction zone, and the monitoring well is equipped with a sensor for acquiring groundwater quality and operating parameters; The control unit is connected to the direct injection unit, electrode strengthening unit, hydraulic circulation unit and monitoring unit respectively, and is used to dynamically adjust the operating parameters of each unit according to the monitoring results.

10. The system according to claim 9, characterized in that, The direct-drive injection unit is an integrated direct-drive drilling-injection equipment that combines direct-drive drilling, hydraulic fracturing, pneumatic fracturing, and atomized injection functions.

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