A soil and groundwater in-situ simultaneous remediation system and method

Abstract

The application provides a soil and groundwater in-situ synchronous remediation system and method, and relates to the field of in-situ remediation of contaminated soil, and comprises a pollution source area partition module, which is used for partitioning the pollution source area according to the concentration distribution of pollutants in the contaminated soil, the pollution depth, the soil water content state and the groundwater flow field. The soil and groundwater in-situ synchronous remediation system and method form a soil-groundwater coupled in-situ reaction zone mainly composed of a pollution source core area and a reaction expansion area through pollution source area partitioning, continuous in-situ reaction zone construction, uniform distribution of remediation medium, groundwater migration regulation and in-situ remediation regulation, so that the contaminated soil, soil pore water and groundwater are in the same remediation range, the directional distribution of the remediation medium in different pollution depth layers and soil-groundwater interaction zones is realized, the contact conditions of the remediation medium and the pollutants are improved, and the stability of the in-situ regeneration process of the contaminated soil is improved.

Description

Technical Field

[0001] This invention relates to the field of in-situ remediation technology for contaminated soil, specifically to a system and method for simultaneous in-situ remediation of soil and groundwater. Background Technology

[0002] Industrial relocation sites, chemical production sites, mining areas, oil storage and transportation areas, and landfill sites commonly experience combined soil and groundwater contamination. After entering the site, pollutants are adsorbed onto soil particle surfaces or remain in soil pores. Some pollutants enter groundwater and migrate with water flow. Current site remediation technologies commonly treat contaminated soil using methods such as excavation and removal, ex-situ leaching, thermal desorption, solidification and stabilization, in-situ chemical oxidation, in-situ chemical reduction, and microbial remediation. Groundwater is often treated using methods such as extraction, recharge and circulation, permeable reactive barriers, hydraulic interception, in-situ chemical injection, and biostimulation. During project implementation, technicians deploy remediation wells, injection wells, extraction wells, monitoring wells, and supporting pipelines based on the type of pollutant, contamination depth, groundwater depth, soil permeability, site boundary conditions, and subsequent land use needs. The remediation process includes chemical dosing, groundwater circulation, and pollutant monitoring for the control and remediation of soil and groundwater within the contaminated area.

[0003] Existing remediation technologies for combined soil and groundwater pollution often focus on groundwater extraction or single-point reagent injection, failing to construct continuous and controllable in-situ reaction zones around the pollution source area. Uneven distribution of remediation media in contaminated soil and insufficient contact between pollutants and the media hinder the stable in-situ removal, degradation, fixation, or migration control of pollutants, resulting in unstable soil regeneration. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a soil and groundwater in-situ synchronous remediation system and method. The technical problem this invention aims to solve is: how to construct continuous in-situ reaction zones by partitioning and synergistically regulate the migration of remediation media and groundwater, thereby addressing the issues of uneven distribution of remediation media, insufficient contact with pollutants, and unstable soil regeneration effects in the remediation of complex pollution.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a soil and groundwater in-situ synchronous remediation system, comprising: The pollution source zoning module is used to divide the contaminated site into the pollution source core area, reaction expansion area and migration control area based on the concentration distribution of pollutants in the contaminated soil, the depth of pollution, the soil moisture content and the groundwater flow field, and to determine the remediation media requirements for each zone. The continuous in-situ reaction zone construction module is used to form a continuous soil-groundwater coupled in-situ reaction zone in the core area of ​​the pollution source and the reaction extension area based on the zoning results of the pollution source zoning module, and to make the soil-groundwater coupled in-situ reaction zone cover the interaction area of ​​polluted soil, soil pore water and groundwater. The remediation medium distribution module is used to add remediation medium to the soil-groundwater coupled in-situ reaction zone according to the remediation medium action requirements corresponding to the core area of ​​the pollution source, the reaction expansion zone and the migration control zone, and to regulate the diffusion range, residence time and action intensity of the remediation medium in different depth layers of the contaminated soil and the soil-groundwater interaction zone, and to determine the coverage state of the soil-groundwater coupled in-situ reaction zone according to the diffusion range. The groundwater migration control module is used to determine groundwater migration control parameters based on the remediation medium's functional requirements and its diffusion range within the soil-groundwater coupling in-situ reaction zone. These groundwater migration control parameters include groundwater flow direction control parameters, groundwater flow velocity control parameters, and hydraulic gradient control parameters. The groundwater flow direction control parameters correspond to the diffusion range, the groundwater flow velocity control parameters correspond to the residence time, and the hydraulic gradient control parameters correspond to the boundary of the migration control zone. The in-situ remediation control module is used to modify the application layer, application amount, application frequency, and groundwater migration control parameters of the remediation medium based on the pollutant concentration in the contaminated soil, groundwater level, groundwater flow velocity, residual amount of remediation medium, and coverage status of the soil-groundwater coupled in-situ reaction zone.

[0006] Preferably, the remediation medium action requirements include the type of remediation medium, the amount added per unit soil mass, the target action depth, the target residence time, and the target action intensity for each zone. The amount added per unit soil mass and the target action intensity for the core pollution source zone are greater than those for the reaction expansion zone. The remediation medium action requirements for the migration control zone include the boundary addition layer, the boundary addition amount, and the boundary action width. The remediation medium action requirements for the migration control zone are used to set the pollutant migration control boundary.

[0007] Preferably, the continuous in-situ reaction zone construction module includes multiple in-situ reaction units, each in-situ reaction unit corresponding to a depth layer of contaminated soil, and the remediation media action range of adjacent in-situ reaction units has an overlapping section in the horizontal or depth direction, the overlapping section being located in the core area of ​​the pollution source or the reaction extension zone.

[0008] Preferably, the soil-groundwater coupled in-situ reaction zone includes a core reaction section covering the core area of ​​the pollution source and an extended reaction section covering the reaction extension area, wherein the core reaction section and the extended reaction section are continuously connected at the boundary.

[0009] Preferably, the remediation medium distribution module adds remediation medium according to the depth layers of contaminated soil, and sets the addition pressure, addition flow rate and addition time for each depth layer. The target addition layer of the remediation medium is the contaminated soil layer where the pollutant concentration is higher than the site remediation target value.

[0010] Preferably, the remediation medium distribution module adopts one of the following dosing methods: segmented dosing, pulsed dosing, or cyclic dosing. The segmented dosing corresponds to different contamination depths, the pulsed dosing corresponds to a preset dosing interval, and the cyclic dosing corresponds to a preset cycle.

[0011] Preferably, the groundwater migration control module includes a flow direction adjustment unit, a flow velocity adjustment unit, and a hydraulic gradient adjustment unit. The flow direction adjustment unit is used to set the groundwater flow direction control parameters, the flow velocity adjustment unit is used to set the groundwater flow velocity control parameters, and the hydraulic gradient adjustment unit is used to set the hydraulic gradient control parameters.

[0012] Preferably, the groundwater migration control module uses the difference between the groundwater flow velocity and the diffusion rate of the remediation medium as a matching parameter for the groundwater flow process and the diffusion process of the remediation medium. The matching parameter serves as the basis for correcting the groundwater migration control parameters, which also include pumping intensity, recharge intensity, and control duration.

[0013] Preferably, the in-situ remediation control module determines the coverage boundary of the remediation medium in the contaminated soil based on the coverage status of the soil-groundwater coupled in-situ reaction zone, and when the coverage boundary does not cover the target contaminated layer, it corrects the remediation medium dosage, dosage frequency, and groundwater migration control parameters corresponding to the target contaminated layer; the target contaminated layer is a contaminated soil layer with a pollutant concentration higher than the site remediation target value.

[0014] A method for simultaneous in-situ remediation of soil and groundwater includes: S1. Based on the concentration distribution of pollutants in the contaminated soil, the depth of contamination, the soil moisture content and the groundwater flow field, determine the core area of ​​the contaminated site, the reaction expansion area and the migration control area, and determine the remediation media requirements for each zone. S2. Based on the zoning results of the contaminated site, a continuous soil-groundwater coupled in-situ reaction zone is constructed within the core area of ​​the pollution source and the reaction extension zone, and the soil-groundwater coupled in-situ reaction zone covers the interaction area of ​​contaminated soil, soil pore water and groundwater. S3. According to the remediation media action requirements corresponding to the core pollution source area, the reaction expansion area and the migration control area, add remediation media to the soil-groundwater coupled in-situ reaction zone, and adjust the diffusion range, residence time and action intensity of the remediation media in different depth layers of polluted soil and soil-groundwater interaction zone, and determine the coverage state of the soil-groundwater coupled in-situ reaction zone according to the diffusion range. S4. Based on the remediation medium's functional requirements and the diffusion range of the remediation medium within the soil-groundwater coupling in-situ reaction zone, determine groundwater migration control parameters. These groundwater migration control parameters include groundwater flow direction control parameters, groundwater flow velocity control parameters, and hydraulic gradient control parameters. The groundwater flow direction control parameters correspond to the diffusion range, the groundwater flow velocity control parameters correspond to the residence time, and the hydraulic gradient control parameters correspond to the boundary of the migration control zone. S5. Based on the pollutant concentration in the contaminated soil, groundwater level, groundwater flow velocity, residual amount of remediation medium, and coverage status of the soil-groundwater coupled in-situ reaction zone, modify the application layer, application amount, application frequency of the remediation medium, and groundwater migration control parameters.

[0015] This invention provides a system and method for in-situ simultaneous remediation of soil and groundwater. It has the following beneficial effects: This soil and groundwater in-situ synchronous remediation system and method, through the zoning of pollution source areas, the construction of continuous in-situ reaction zones, the uniform distribution and addition of remediation media, the regulation of groundwater migration, and the regulation of in-situ remediation, forms a soil-groundwater coupled in-situ reaction zone with the core pollution source area and the reaction extension area as the main components. This places contaminated soil, soil pore water, and groundwater within the same remediation range, achieves the directional distribution of remediation media in different pollution depth layers and soil-groundwater interaction zones, improves the contact conditions between remediation media and pollutants, and enhances the stability of the in-situ regeneration process of contaminated soil.

[0016] The remediation media requirements are determined by dividing the pollution source core area, reaction expansion area, and migration control area. A control method is adopted that corresponds the groundwater migration regulation parameters with the diffusion range, residence time, and migration control area boundary of the remediation media. This ensures that the remediation media addition process and the groundwater migration process are coordinated, reducing the uneven distribution of remediation media and the risk of pollutant migration. The in-situ remediation regulation module adjusts the addition parameters and groundwater migration regulation parameters according to the coverage status, pollutant concentration, groundwater level, groundwater flow velocity, and residual amount of remediation media, so as to maintain continuous coverage of the soil-groundwater coupled in-situ reaction zone. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the system module composition and data flow of the present invention; Figure 2 This is a schematic diagram illustrating the zoning and functional requirements of the contaminated site according to the present invention; Figure 3 This is a schematic diagram illustrating the construction and connection of the continuous in-situ reaction zone of the present invention; Figure 4 This is a schematic diagram illustrating the method and control of the repair medium addition in this invention; Figure 5 This is a flowchart of the in-situ synchronous repair method of the present invention. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention have been clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1 like Figure 1-5 As shown, this embodiment of the invention provides a soil and groundwater in-situ synchronous remediation system, comprising: The pollution source zoning module is used to divide a contaminated site into a core pollution source zone, a reaction expansion zone, and a migration control zone based on the concentration distribution of pollutants in the contaminated soil, the depth of contamination, the soil moisture content, and the groundwater flow field. It also determines the remediation media requirements for each zone. These requirements include the type of remediation media, the dosage per unit soil volume, the target depth of action, the target residence time, and the target intensity of action for each zone. The dosage per unit soil volume and the target intensity of action for the core pollution source zone are greater than those for the reaction expansion zone. The remediation media requirements for the migration control zone include the boundary application layer, the boundary application volume, and the boundary action width. These requirements are used to set the pollutant migration control boundaries.

[0020] The continuous in-situ reaction zone construction module is used to form a continuous soil-groundwater coupled in-situ reaction zone within the core area and reaction extension area of ​​the pollution source, based on the zoning results of the pollution source zoning module. This module covers the interaction area of ​​contaminated soil, soil pore water, and groundwater. The continuous in-situ reaction zone construction module includes multiple in-situ reaction units, each corresponding to a depth layer of the contaminated soil. The remediation media action ranges of adjacent in-situ reaction units overlap in the horizontal or depth direction, with the overlapping sections located within the core area or reaction extension area of ​​the pollution source. The soil-groundwater coupled in-situ reaction zone includes a core reaction section covering the core area of ​​the pollution source and an extension reaction section covering the reaction extension area, with the core and extension reaction sections continuously connected at their boundaries.

[0021] The remediation medium distribution module is used to add remediation media to the soil-groundwater coupled in-situ reaction zone according to the remediation media action requirements corresponding to the core area, reaction expansion zone, and migration control zone of the pollution source. It also controls the diffusion range, residence time, and intensity of the remediation media at different depths of contaminated soil and in the soil-groundwater interaction zone, determining the coverage state of the soil-groundwater coupled in-situ reaction zone based on the diffusion range. The module adds remediation media according to the depth layers of contaminated soil, setting the addition pressure, flow rate, and addition time for each depth layer. The target addition layer is the contaminated soil layer with a pollutant concentration higher than the site remediation target value. The module employs one of the following addition methods: segmented addition, pulsed addition, or cyclic addition. Segmented addition corresponds to different contaminated depth layers, pulsed addition corresponds to a preset addition interval, and cyclic addition corresponds to a preset cycle.

[0022] The groundwater migration control module is used to determine groundwater migration control parameters based on the remediation medium's functional requirements and its diffusion range within the soil-groundwater coupling in-situ reaction zone. These parameters include groundwater flow direction control parameters, groundwater velocity control parameters, and hydraulic gradient control parameters. The groundwater flow direction control parameter corresponds to the diffusion range, the groundwater velocity control parameter corresponds to the residence time, and the hydraulic gradient control parameter corresponds to the boundary of the migration control zone. The module includes a flow direction adjustment unit, a velocity adjustment unit, and a hydraulic gradient adjustment unit. The flow direction adjustment unit sets the groundwater flow direction control parameters, the velocity adjustment unit sets the groundwater velocity control parameters, and the hydraulic gradient adjustment unit sets the hydraulic gradient control parameters. The module uses the difference between the groundwater velocity and the remediation medium diffusion rate as a matching parameter between the groundwater flow process and the remediation medium diffusion process. This matching parameter serves as the basis for correcting the groundwater migration control parameters, which also include pumping intensity, recharge intensity, and control duration.

[0023] The in-situ remediation control module is used to adjust the application layer, dosage, and frequency of the remediation medium, as well as groundwater migration control parameters, based on pollutant concentration in the contaminated soil, groundwater level, groundwater flow velocity, residual remediation medium, and the cover status of the soil-groundwater coupled in-situ reaction zone. The module determines the coverage boundary of the remediation medium in the contaminated soil based on the cover status of the soil-groundwater coupled in-situ reaction zone. If the coverage boundary does not cover the target contaminated layer, the module adjusts the application volume, frequency, and groundwater migration control parameters of the remediation medium corresponding to the target contaminated layer. The target contaminated layer is the contaminated soil layer with a pollutant concentration higher than the site remediation target value.

[0024] A method for simultaneous in-situ remediation of soil and groundwater includes: S1. Based on the concentration distribution of pollutants in the contaminated soil, the depth of contamination, the soil moisture content and the groundwater flow field, determine the core area of ​​the contaminated site, the reaction expansion area and the migration control area, and determine the remediation media requirements for each zone.

[0025] S2. Based on the zoning results of the contaminated site, a continuous soil-groundwater coupled in-situ reaction zone is constructed within the core area of ​​the pollution source and the reaction extension area, and the soil-groundwater coupled in-situ reaction zone covers the interaction area of ​​contaminated soil, soil pore water and groundwater.

[0026] S3. According to the remediation media requirements corresponding to the core area of ​​the pollution source, the reaction expansion area and the migration control area, add remediation media to the soil-groundwater coupling in-situ reaction zone, and regulate the diffusion range, residence time and intensity of the remediation media in different depth layers of the polluted soil and the soil-groundwater interaction zone. Determine the coverage status of the soil-groundwater coupling in-situ reaction zone based on the diffusion range.

[0027] S4. Based on the remediation medium's functional requirements and its diffusion range within the soil-groundwater coupling in-situ reaction zone, determine the groundwater migration control parameters. These parameters include groundwater flow direction control parameters, groundwater velocity control parameters, and hydraulic gradient control parameters. The groundwater flow direction control parameters correspond to the diffusion range, the groundwater velocity control parameters correspond to the residence time, and the hydraulic gradient control parameters correspond to the boundary of the migration control zone.

[0028] S5. Based on the pollutant concentration in the contaminated soil, groundwater level, groundwater flow velocity, residual amount of remediation media, and coverage status of the soil-groundwater coupled in-situ reaction zone, modify the remediation media addition layer, addition amount, addition frequency, and groundwater migration control parameters.

[0029] The remediation medium distribution module selects a segmented dosing method based on the contamination depth. Segmented dosing includes setting the dosing layer, dosing pressure, dosing flow rate, and dosing time for different contamination depths in the contaminated soil. Depth layers with contaminant concentrations higher than the site remediation target value are designated as target dosing layers, and the dosing volume or time per unit soil volume corresponding to the target dosing layer is greater than the dosing volume or time per unit soil volume corresponding to non-target dosing layers.

[0030] The pulse dosing method is selected based on the preset dosing interval. Pulse dosing includes intermittent dosing according to the preset dosing cycle, with a residence period between adjacent dosings. The preset dosing interval is determined based on the diffusion rate of the remediation medium in the contaminated soil, the target residence time required for the remediation medium's effectiveness, and the groundwater flow rate.

[0031] The cyclical dosing method is selected according to the preset cycle. Cyclic dosing includes repeatedly performing dosing, retention, and replenishment according to the preset cycle. The preset cycle is determined based on changes in pollutant concentration in the contaminated soil, the residual amount of remediation media, and the coverage status of the soil-groundwater coupled in-situ reaction zone.

[0032] Example 2 This embodiment is used to verify that by dividing the area into zones, layering reaction units, and adding remediation media in stages, a continuous soil-groundwater coupled in-situ reaction zone can be formed in the core area of ​​the pollution source and the reaction extension zone.

[0033] 1. Site conditions This embodiment selects a decommissioned chemical plant site as the remediation target. The remediation area has a planar dimension of 36m × 24m, a groundwater depth of 4.6m to 5.2m, and contaminated soil is mainly distributed within a depth range of 2.5m to 8.5m. The groundwater at the site generally flows from northwest to southeast, with an average groundwater flow velocity of 0.18m / d, a hydraulic gradient of 0.0035, and a soil moisture content of 22% to 31%.

[0034] The main pollutants at the site are trichloroethylene and cis-1,2-dichloroethylene. The trichloroethylene concentration in the core area of ​​the pollution source ranges from 38 mg / kg to 92 mg / kg, while the concentration in the reaction extension area ranges from 6 mg / kg to 35 mg / kg. The target remediation concentration for the site is 5 mg / kg of trichloroethylene.

[0035] 2. Zoning of pollution sources Based on pollutant concentration distribution, pollution depth, soil moisture content, and groundwater flow field, the contaminated site was divided into a pollution source core area, a reaction expansion area, and a migration control area. The contaminated soil area with a trichloroethylene concentration greater than 30 mg / kg and continuous distribution was designated as the pollution source core area; the area with a trichloroethylene concentration between 5 mg / kg and 30 mg / kg was designated as the reaction expansion area; and the area extending 5 m downstream from the reaction expansion area along the groundwater flow was designated as the migration control area.

[0036] The core area of ​​the pollution source has a planar dimension of 14m × 10m, with a pollution depth ranging from 3.0m to 8.5m. The reaction extension zone is set out along the outer side of the core area of ​​the pollution source, with an outward width of 5m and a pollution depth ranging from 2.5m to 8.5m. The migration control zone is located downstream of the groundwater, with a width of 5m and an action depth ranging from 4.0m to 8.5m, and covers the action range of the remediation media at the adjacent boundary application points.

[0037] The soil dosage per unit volume in the core pollution source area is set at 8.0 kg / m³, with a target residence time of 72 h. The soil dosage per unit volume in the reaction expansion zone is set at 4.5 kg / m³, with a target residence time of 48 h. The soil dosage per unit volume at the boundary of the migration control zone is set at 2.0 kg / m³, with a boundary width of 5 m.

[0038] 3. Construction of continuous in-situ reaction zones A soil-groundwater coupled in-situ reaction zone was constructed within the core area of ​​the pollution source and the reaction extension zone. The in-situ reaction zone was divided into three depth layers according to the depth of pollution: The first depth layer is 2.5m to 4.5m, the second depth layer is 4.5m to 6.5m, and the third depth layer is 6.5m to 8.5m.

[0039] For each planar point, in-situ reaction units are set up at three depth layers, with each in-situ reaction unit corresponding to one depth layer of contaminated soil. Within the same depth layer, the designed radius of action of the in-situ reaction units corresponding to adjacent planar points is 2.0m, and the distance between planar points is 3.0m.

[0040] Within the same depth layer, the designed effective radius of the in-situ reaction unit corresponding to adjacent planar points is 2.0m, the spacing between planar points is 3.0m, and adjacent in-situ reaction units form a 1.0m overlap in the horizontal direction. Within the same planar point, the in-situ reaction units corresponding to adjacent depth layers above and below form an overlap of 0.3m to 0.5m in the depth direction.

[0041] A core reaction section is set up in the core area of ​​the pollution source, with in-situ reaction units deployed at a density of 9m². 2 One. An extended reaction section is set up in the reaction extension zone, with in-situ reaction units arranged at a density of 12m². 2 one.

[0042] The core area of ​​the pollution source is 140 m², with 16 planar monitoring points. Each planar monitoring point corresponds to three in-situ reaction units at three depth levels, for a total of 48 in-situ reaction units. The reaction extension zone extends 5 m outward from the core area, covering an area of ​​340 m², with 29 planar monitoring points. Each planar monitoring point corresponds to three in-situ reaction units at three depth levels, for a total of 87 in-situ reaction units. The core reaction zone and the extension reaction zone are continuously connected at the boundary.

[0043] 4. Addition of repair media Persulfate-based oxidative remediation media was used. The remediation media was prepared from sodium persulfate, ferrous sulfate, and sodium bicarbonate, with a sodium persulfate concentration of 80 g / L, a ferrous sulfate concentration of 6 g / L, and a sodium bicarbonate concentration of 3 g / L.

[0044] The remediation medium was added in stages according to depth. Within the core area of ​​the pollution source, the addition pressure for the first depth layer was 0.14 MPa, and the addition flow rate was 0.50 m³ / s. 3 / h, single-point dosing time is 1.0h. The dosing pressure at the second depth level is 0.20MPa, and the dosing flow rate is 0.70m³ / h. 3 The injection rate is 0.24 MPa / h, and the single-point injection time is 1.5 h. The injection pressure at the third depth level is 0.24 MPa, and the injection flow rate is 0.60 m³ / h. 3 / h, with a single-point dosing time of 1.5h. Within the reaction propagation zone, the dosing rate at the first depth layer is 0.30m. 3 At point / , the injection rate at the second depth level is 0.50m. 3 At point / , the injection rate at the third depth level is 0.40m. 3 / point.

[0045] Within the core area of ​​the pollution source, each planar location corresponds to three in-situ reaction units. The dosage of the in-situ reaction units corresponding to the first, second, and third depth layers is 0.50m³. 3 1.05m 3 and 0.90m 3 Within the reaction extension zone, the total dosage at each planar point was 1.20 mm. 3 Within the migration control zone, the amount of remediation medium added at each boundary application point is 0.70 m³. 3 .

[0046] The dosage per unit soil volume is calculated based on the effective component of sodium persulfate. Within the core area of ​​the pollution source, the target soil volume corresponding to a single planar point is 24.5 m³. 3 The effective component dosage of sodium persulfate is 196 kg, corresponding to a dosage of 8.0 kg / m² of soil. 3 Within the reaction extension zone, the target soil volume corresponding to a single planar point is 21.3 m³. 3 The effective component dosage of sodium persulfate is 96 kg, corresponding to a dosage of 4.5 kg / m² of soil. 3 .

[0047] The order of application is: core pollution source zone, reaction expansion zone, and migration control zone. In the core pollution source zone, an stratified application sequence is used from bottom to top, with the third depth layer, second depth layer, and first depth layer applied sequentially. In the reaction expansion zone, an outward, row-by-row application method is used.

[0048] 5. Coverage Status Determination To determine the diffusion range of the remediation medium, a bromide ion tracer component was added to the remediation medium at a concentration of 0.5 g / L. Soil pore water and groundwater samples were collected at 24 h, 48 h, and 72 h after addition. The data from the 24 h and 72 h samples were used to verify the diffusion trend of the remediation medium.

[0049] Twelve monitoring points were set up at each depth in both the core pollution source area and the reaction expansion zone, with a spacing of 3 meters between the monitoring points. Soil pore water samples were collected at each monitoring point corresponding to the depth; groundwater samples were collected simultaneously at monitoring points located below the groundwater depth.

[0050] When the bromide ion concentration at a monitoring point is not less than 30 mg / L and the residual persulfate concentration is not less than 2 g / L, the layer where the monitoring point is located is determined to be a remediation medium covering layer. When adjacent monitoring points all meet the above conditions, the area between adjacent monitoring points is determined to be a covered area. The coverage rate is calculated as the ratio of the number of monitoring points that meet the coverage determination conditions to the total number of monitoring points at the depth layer.

[0051] Forty-eight hours after application, the number of monitoring points meeting the coverage criteria in the first, second, and third depth layers of the core pollution source area were 11, 12, and 11, respectively, corresponding to coverage rates of 91.7%, 100%, and 91.7%. In the reaction extension zone, the number of monitoring points meeting the coverage criteria in the first, second, and third depth layers were 10, 11, and 10, respectively, corresponding to coverage rates of 83.3%, 91.7%, and 83.3%. The coverage width of the migration control zone boundary ranged from 4.6m to 5.2m.

[0052] 6. Supplementary dosing Based on the cover status, the southeastern edge of the third depth layer in the reaction extension zone is undercovered, with an area of ​​28m². 2 Six supplementary application points were set up in the area, with 0.6m³ of repair medium added at each point. 3 The injection pressure is 0.22 MPa, and the injection flow rate is 0.55 m³ / h. 3 / h, the single-point dosing time is 1.1h.

[0053] 72 hours after the supplementary dosing was completed, 12 monitoring points at each of the three depth layers in the core pollution source area met the coverage criteria, corresponding to a coverage rate of 100%. In the reaction expansion zone, the number of monitoring points meeting the coverage criteria at the first, second, and third depth layers were 11, 12, and 11, respectively, corresponding to coverage rates of 91.7%, 100%, and 91.7%. Notably, the coverage rate at the third depth layer in the reaction expansion zone increased from 83.3% to 91.7%, and all monitoring points surrounding the six supplementary dosing points within the supplementary dosing area met the coverage criteria.

[0054] The above test results show that the stratified continuous reaction zone and the segmented application method correspond to the coverage status determination of the core pollution source area, the reaction extension zone, and the soil-groundwater interaction zone. After supplementary application, the coverage rate of the third depth layer in the reaction extension zone increased from 83.3% to 91.7% in areas with insufficient coverage. The coverage status is used to determine the supplementary application area, the supplementary application amount, and the supplementary application frequency.

[0055] Example 3 This embodiment illustrates the implementation process of feedback correction of groundwater migration control parameters and remediation medium addition parameters based on the remediation medium coverage status.

[0056] 1. Site conditions This example is applied to a decommissioned chemical plant site. The contaminated area is 36m long and 22m wide, with groundwater depth ranging from 3.2m to 3.8m. The main contaminated layers are located 2.5m to 7.0m below the surface. The initial groundwater flow direction is northwest to southeast, with an average groundwater flow velocity of 0.11m / d. The soil moisture content in the core pollution source area is 18% to 24%, in the reaction expansion area it is 16% to 21%, and in the migration control area it is 15% to 19%.

[0057] The pollutants include trichloroethylene and benzene. Within the core area of ​​the pollution source, the highest concentration of trichloroethylene in the soil was 186 mg / kg, and the highest concentration of benzene was 73 mg / kg. The highest concentration of trichloroethylene in groundwater was 2.8 mg / L, and the highest concentration of benzene was 1.1 mg / L. The site remediation target values ​​for trichloroethylene in soil are 40 mg / kg and for benzene are 20 mg / kg. The control target values ​​for trichloroethylene in groundwater are 0.7 mg / L and for benzene are 0.3 mg / L.

[0058] 2. Zoning of pollution sources Based on pollutant concentration distribution, pollution depth, soil moisture content, and groundwater flow field, the contaminated site is divided into a pollution source core area, a reaction expansion area, and a migration control area.

[0059] Specifically, areas with soil trichloroethylene concentrations above 40 mg / kg or benzene concentrations above 20 mg / kg, and pollution depths continuously distributed between 3.0 m and 6.5 m, are designated as pollution source core areas. Areas located outside the pollution source core areas, with pollutant concentrations lower than those in the pollution source core areas but still higher than the site remediation target values, are designated as reaction extension areas. Areas located downstream of groundwater and adjacent to the reaction extension areas are designated as migration control areas.

[0060] The core area of ​​the pollution source is 12m × 9m, with a pollution depth ranging from 3.0m to 6.5m. The reaction extension zone extends outward from the outer edge of the core area by 4m to 6m. The migration control zone is located downstream of the groundwater and is 5m wide. The target residence time is determined based on the residual time of the remediation medium in the soil pore water, the initial groundwater flow velocity, and the thickness of the contaminated layer.

[0061] The soil application rate in the core pollution source area is 18 kg / m³, the target depth is 6.5 m, and the target residence time is 72 h. In the reaction extension zone, the soil application rate is 10 kg / m³, the target depth is 6.0 m, and the target residence time is 48 h. The boundary application layer in the migration control zone is from 3.5 m to 6.5 m, and the boundary width is 5 m.

[0062] 3. Construction of in-situ reaction zone coupled with soil and groundwater A soil-groundwater coupled in-situ reaction zone is constructed within the core area of ​​the pollution source and the reaction extension zone, which includes a core reaction section covering the core area of ​​the pollution source and an extended reaction section covering the reaction extension zone.

[0063] Adjacent in-situ reaction units form overlapping sections of 1.2m to 1.8m in the horizontal direction and 0.5m to 0.8m in the depth direction. The overlapping sections are located within the core area of ​​the pollution source and the reaction extension area, ensuring continuous connection between the core reaction section and the extension reaction section.

[0064] 4. Determining the application of repair media and coverage status. The remediation medium is a mixture of persulfate composite activator and adsorption-fixing material. The residual persulfate concentration of not less than 5 mg / L is used as the threshold for determining the coverage of the remediation medium. The persulfate mass concentration is 80 g / L, the activator mass concentration is 12 g / L, and the solid content of the adsorption-fixing material slurry is 6%.

[0065] The remediation medium is added in three layers according to the contamination depth. The first layer is from 2.5m to 4.0m, with an addition pressure of 0.18MPa and a flow rate of 0.35m³ / h. The second layer is from 4.0m to 5.5m, with an addition pressure of 0.22MPa and a flow rate of 0.42m³ / h. The third layer is from 5.5m to 7.0m, with an addition pressure of 0.25MPa and a flow rate of 0.46m³ / h.

[0066] Pulsed dosing was used in the core pollution source area, with a single dosing time of 2 hours and a dosing interval of 10 hours, for a total of 3 cycles. Segmented dosing was used in the reaction expansion zone, with a single-layer dosing time of 1.5 hours. Cyclic dosing was used in the migration control zone, with a cycle of 24 hours. Coverage status was determined by residual persulfate detection at monitoring points and coverage boundary interpolation. The design boundary was the outer control line of the downstream boundary of the core reaction zone, the expansion reaction zone, and the migration control zone. The coverage ratio was the ratio of the area reaching the coverage threshold to the area within the corresponding design boundary. Coverage boundary interpolation was determined based on the persulfate residual levels at adjacent monitoring points.

[0067] Coverage status was checked 24 hours after application. The coverage rate of the core reaction zone was 92%. The coverage rate of the extended reaction zone was 76%. The coverage rate of the downstream boundary of the migration control zone was 68%. Among them, the residual amount downstream of the 4.0m to 5.5m layer in the extended reaction zone was lower than the coverage judgment threshold, and the coverage rate of the 3.5m to 6.5m boundary layer in the migration control zone was lower than the design requirements.

[0068] 5. Determination of groundwater migration regulation parameters Groundwater migration control parameters are determined based on the remediation medium's functional requirements and diffusion range. The groundwater flow direction control parameter is set from the core reaction zone to the extended reaction zone. The groundwater velocity control parameter is set to 0.06 m / d to 0.08 m / d, corresponding to the 72-hour target residence time in the core area of ​​the pollution source, and is lower than the initial average groundwater velocity of 0.11 m / d at the site. The hydraulic gradient control parameter is set to 0.004 to 0.006.

[0069] The downstream pumping intensity is set to 1.6 m³ / h. The upstream reinjection intensity is set to 1.1 m³ / h. The control duration is set to 72 h. These parameters correspond to a 5 m boundary width of the migration control zone. The hydraulic gradient control parameters, downstream pumping intensity, and upstream reinjection intensity are set to correspond to a 5 m boundary width of the migration control zone.

[0070] 6. In-situ repair feedback correction After 36 hours of operation, the measured groundwater flow velocity was 0.10 m / d, and the average outward displacement of the cover boundary within the reaction extension zone was 0.105 m over 36 hours. The average diffusion rate of the remediation medium within the reaction extension zone, calculated based on the outward displacement of the cover boundary and the operating time, was 0.07 m / d. The difference between the groundwater flow velocity and the remediation medium diffusion rate was 0.03 m / d, which was used as a matching parameter for the groundwater flow process and the remediation medium diffusion process. When the coverage ratio of the reaction extension zone was less than 85% and the matching parameter was greater than 0.02 m / d, in-situ remediation feedback correction was triggered.

[0071] In this embodiment, the coverage ratio and matching parameters of the reaction expansion zone are used as the feedback correction trigger conditions. The downstream drainage intensity is corrected from 1.6 m³ / h to 1.2 m³ / h. The upstream recharge intensity is corrected from 1.1 m³ / h to 1.4 m³ / h. The dosage of the second layer of remediation medium is increased by 15%. The second layer corresponds to the 4.0m to 5.5m layer, and the unit soil dosage of this layer within the reaction expansion zone is adjusted from 10 kg / m³ to 11.5 kg / m³. The frequency of the second and third layers is corrected from 3 cycles to 4 cycles.

[0072] After correction, the measured groundwater flow velocity is 0.075 m / d, and the hydraulic gradient remains at 0.005.

[0073] 7. Repair Results After 72 hours of operation, the coverage rate of the core reaction zone was 98%. The coverage rate of the extended reaction zone was 93%. The coverage rate of the downstream boundary of the migration control zone was 90%. The target contaminated layer from 3.0m to 6.5m was located within the coverage boundary of the remediation medium.

[0074] Soil pollutant concentrations were the average of 12 soil sampling points within the core area of ​​the pollution source. In the soil of the core area, the average concentration of trichloroethylene decreased from 112 mg / kg to 39 mg / kg, and the average concentration of benzene decreased from 46 mg / kg to 18 mg / kg. Groundwater pollutant concentrations were the average of samples collected from 6 monitoring wells. The average concentration of trichloroethylene in groundwater decreased from 1.9 mg / L to 0.62 mg / L, and the average concentration of benzene decreased from 0.74 mg / L to 0.21 mg / L.

[0075] After correction, the coverage ratio of the reaction extension zone increased from 76% to 93%, and the coverage ratio of the downstream boundary of the migration control zone increased from 68% to 90%. The target contaminated layer from 3.0m to 6.5m was located within the coverage boundary of the remediation medium. These results indicate that the coverage ratio and matching parameters can be used to correct the remediation medium addition parameters and groundwater migration control parameters.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A soil and groundwater in-situ synchronous remediation system, characterized in that, include: The pollution source zoning module is used to divide the contaminated site into the pollution source core area, reaction expansion area and migration control area based on the concentration distribution of pollutants in the contaminated soil, the depth of pollution, the soil moisture content and the groundwater flow field, and to determine the remediation media requirements for each zone. The continuous in-situ reaction zone construction module is used to form a continuous soil-groundwater coupled in-situ reaction zone in the core area of ​​the pollution source and the reaction extension area based on the zoning results of the pollution source zoning module, and to make the soil-groundwater coupled in-situ reaction zone cover the interaction area of ​​polluted soil, soil pore water and groundwater. The remediation medium distribution module is used to add remediation medium to the soil-groundwater coupled in-situ reaction zone according to the remediation medium action requirements corresponding to the core area of ​​the pollution source, the reaction expansion zone and the migration control zone, and to regulate the diffusion range, residence time and action intensity of the remediation medium in different depth layers of the contaminated soil and the soil-groundwater interaction zone, and to determine the coverage state of the soil-groundwater coupled in-situ reaction zone according to the diffusion range. The groundwater migration control module is used to determine groundwater migration control parameters based on the action requirements of the remediation medium and the diffusion range of the remediation medium in the soil-groundwater coupling in-situ reaction zone. The groundwater migration control parameters include groundwater flow direction control parameters, groundwater flow velocity control parameters, and hydraulic gradient control parameters; the groundwater flow direction control parameters correspond to the diffusion range, the groundwater flow velocity control parameters correspond to the residence time, and the hydraulic gradient control parameters correspond to the boundary of the migration control zone. The in-situ remediation control module is used to modify the application layer, application amount, application frequency, and groundwater migration control parameters of the remediation medium based on the pollutant concentration in the contaminated soil, groundwater level, groundwater flow velocity, residual amount of remediation medium, and coverage status of the soil-groundwater coupled in-situ reaction zone.

2. The soil and groundwater in-situ synchronous remediation system according to claim 1, characterized in that: The remediation medium requirements include the type of remediation medium, the amount added per unit soil mass, the target depth of action, the target residence time, and the target intensity of action for each zone. The amount added per unit soil mass and the target intensity of action for the core pollution source zone are greater than those for the reaction expansion zone. The remediation medium requirements for the migration control zone include the boundary addition layer, the boundary addition amount, and the boundary action width. The remediation medium requirements for the migration control zone are used to set the pollution migration control boundary.

3. The soil and groundwater in-situ synchronous remediation system according to claim 1, characterized in that: The continuous in-situ reaction zone construction module includes multiple in-situ reaction units, each corresponding to a depth layer of contaminated soil. The remediation media action range of adjacent in-situ reaction units overlaps in the horizontal or depth direction, and the overlapping section is located within the core area of ​​the pollution source or the reaction extension zone.

4. The soil and groundwater in-situ synchronous remediation system according to claim 1, characterized in that: The soil-groundwater coupled in-situ reaction zone includes a core reaction section covering the core area of ​​the pollution source and an extended reaction section covering the reaction extension area, with the core reaction section and the extended reaction section continuously connected at the boundary.

5. The soil and groundwater in-situ synchronous remediation system according to claim 1, characterized in that: The remediation medium distribution module adds remediation medium according to the depth layers of contaminated soil, and sets the addition pressure, addition flow rate and addition time for each depth layer. The target addition layer of the remediation medium is the contaminated soil layer where the pollutant concentration is higher than the site remediation target value.

6. The soil and groundwater in-situ synchronous remediation system according to claim 1, characterized in that: The remediation medium distribution module adopts one of the following dosing methods: segmented dosing, pulse dosing, or cyclic dosing. The segmented dosing corresponds to different contamination depth layers, the pulse dosing corresponds to a preset dosing interval, and the cyclic dosing corresponds to a preset cycle.

7. The soil and groundwater in-situ synchronous remediation system according to claim 1, characterized in that: The groundwater migration control module includes a flow direction adjustment unit, a flow velocity adjustment unit, and a hydraulic gradient adjustment unit. The flow direction adjustment unit is used to set the groundwater flow direction control parameters, the flow velocity adjustment unit is used to set the groundwater flow velocity control parameters, and the hydraulic gradient adjustment unit is used to set the hydraulic gradient control parameters.

8. The soil and groundwater in-situ synchronous remediation system according to claim 1, characterized in that: The groundwater migration control module uses the difference between the groundwater flow velocity and the diffusion rate of the remediation medium as a matching parameter for the groundwater flow process and the diffusion process of the remediation medium. The matching parameter serves as the basis for correcting the groundwater migration control parameters, which also include pumping intensity, recharge intensity, and control duration.

9. The soil and groundwater in-situ synchronous remediation system according to claim 1, characterized in that: The in-situ remediation control module determines the coverage boundary of the remediation medium in the contaminated soil based on the coverage status of the soil-groundwater coupled in-situ reaction zone. When the coverage boundary does not cover the target contaminated layer, it corrects the remediation medium dosage, dosage frequency, and groundwater migration control parameters corresponding to the target contaminated layer. The target contaminated layer is the contaminated soil layer with a pollutant concentration higher than the site remediation target value.

10. A method for in-situ simultaneous remediation of soil and groundwater, characterized in that, include: S1. Based on the concentration distribution of pollutants in the contaminated soil, the depth of contamination, the soil moisture content and the groundwater flow field, determine the core area of ​​the contaminated site, the reaction expansion area and the migration control area, and determine the remediation media requirements for each zone. S2. Based on the zoning results of the contaminated site, a continuous soil-groundwater coupled in-situ reaction zone is constructed within the core area of ​​the pollution source and the reaction extension zone, and the soil-groundwater coupled in-situ reaction zone covers the interaction area of ​​contaminated soil, soil pore water and groundwater. S3. According to the remediation media action requirements corresponding to the core pollution source area, the reaction expansion area and the migration control area, add remediation media to the soil-groundwater coupled in-situ reaction zone, and adjust the diffusion range, residence time and action intensity of the remediation media in different depth layers of polluted soil and soil-groundwater interaction zone, and determine the coverage state of the soil-groundwater coupled in-situ reaction zone according to the diffusion range. S4. Based on the remediation medium's functional requirements and the diffusion range of the remediation medium within the soil-groundwater coupling in-situ reaction zone, determine groundwater migration control parameters. These groundwater migration control parameters include groundwater flow direction control parameters, groundwater flow velocity control parameters, and hydraulic gradient control parameters. The groundwater flow direction control parameters correspond to the diffusion range, the groundwater flow velocity control parameters correspond to the residence time, and the hydraulic gradient control parameters correspond to the boundary of the migration control zone. S5. Based on the pollutant concentration in the contaminated soil, groundwater level, groundwater flow velocity, residual amount of remediation medium, and coverage status of the soil-groundwater coupled in-situ reaction zone, modify the application layer, application amount, application frequency, and groundwater migration control parameters of the remediation medium.

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