An isco repair system and method of repair

Abstract

The application discloses an ISCO remediation system and a remediation method, and the remediation system comprises a multiphase extraction well, a groundwater circulation well and an auxiliary injection well, the multiphase extraction well is connected with a first ground system, the groundwater circulation well is connected with a second ground system, and the auxiliary injection well is connected with a third ground system. The method comprises the following steps: S1, pollution assessment; S2, remediation of a simple soil pollution area; S3, remediation of a simple groundwater pollution area; and S4, remediation of a soil and groundwater composite pollution area. The application provides various remediation wells with different structures aiming at various pollution conditions of soil and groundwater, can realize extraction of NAPL and multi-point synchronous injection of a remediation agent, realizes the purpose of shrinking the boundary of a pollution plume, and thus can achieve good remediation effect and remediation efficiency in a short term and a long term, and has important practical significance for ISCO remediation of soil and groundwater.

Description

Technical Field

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

[0002] In-situ chemical oxidation (ISCO) is an environmental remediation technology used to remediate contaminated soil and groundwater. It involves injecting oxidants into the contaminated area to decompose organic pollutants (such as petroleum hydrocarbons, benzene compounds, chlorinated hydrocarbons, etc.) into harmless or less toxic substances.

[0003] Before and after ISCO remediation, it is usually necessary to establish a complete ISCO remediation system, such as determining the type, concentration, distribution and hydrogeological conditions (permeability, pH, organic matter content, etc.) of pollutants; matching oxidants according to the characteristics of pollutants, calculating the dosage and injection method (such as injection wells, permeable reactive walls, etc.); injecting oxidant solutions into the contaminated area through vertical / horizontal injection wells, or using stirring (shallow soil); and monitoring pollutant concentrations, oxidant residues, byproducts (such as chloride ions) and changes in groundwater chemistry.

[0004] Previous studies have touched upon related ISCO remediation systems. For example, patent publication number CN117102229A provides an optimization model for in-situ thermally activated persulfate oxidation remediation technology parameters for petroleum hydrocarbon contaminated soil. This optimization model covers parameters that significantly affect the final removal efficiency of petroleum hydrocarbons, such as soil properties, petroleum hydrocarbon characteristics, heating energy, persulfate consumption, and its transport technology. It also quantitatively characterizes the impact of these parameter changes on petroleum hydrocarbon removal efficiency. This invention can be applied to the optimization of in-situ thermally activated persulfate remediation technology parameters for different petroleum hydrocarbon contaminated sites, providing technical guidance for achieving precise remediation of contaminated sites. However, although many studies have investigated the ISCO system, problems remain, such as uneven oxidant distribution due to geological heterogeneity. Furthermore, the presence of non-aqueous liquid pollutants (NAPL) can also affect the in-situ chemical oxidation effect, which is difficult to completely resolve. Therefore, a more comprehensive ISCO remediation system is needed to alleviate this problem. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides an ISCO repair system and repair method.

[0006] The technical solution of this invention is:

[0007] An ISCO remediation system includes a multiphase extraction well, a groundwater circulation well, and an auxiliary injection well;

[0008] The multiphase extraction well is connected to the first surface system, the groundwater circulation well is connected to the second surface system, and the auxiliary injection well is connected to the third surface system.

[0009] The first surface system includes a first pneumatic pump, a gas-liquid separation tank, an oil-gas separation tank, and a liquid storage tank connected in sequence;

[0010] The second surface system includes two second pneumatic pumps, a water tank and an activated carbon adsorption tank connected in sequence to one of the second pneumatic pumps, and a first reagent tank connected in sequence to the other second pneumatic pump;

[0011] The third surface system includes a third pneumatic pump, a second reagent tank, and a temporary storage tank connected in sequence.

[0012] The groundwater circulation well is equipped with a packer, and a submersible pump is located below the packer.

[0013] Furthermore, the first pneumatic pump is connected to the interior of the multiphase extraction well via a first conduit, and the third pneumatic pump is connected to the interior of the auxiliary injection well via a third conduit.

[0014] Explanation: The process of injecting chemical oxidizing agents and extracting groundwater is achieved through conduits.

[0015] Furthermore, the groundwater circulation well is also equipped with an injection pipe. The bottom of the injection pipe is threaded and sealed to the middle of the upper surface of the packer. Several grooves are evenly spaced around the bottom side wall of the injection pipe. A compression pipe is provided at the bottom of the groove. The front end of the compression pipe is provided with a plug and extends out of the groove. The rear end of the compression pipe is connected to and sealed with the injection pipe inside the groove. A telescopic rod is provided inside the groove. The end of the telescopic rod is connected to the plug through a shovel. A guide pipe is fixedly provided in the middle of one side of the shovel. The well wall of the groundwater circulation well at the corresponding position of each guide pipe is provided with a corresponding opening. A spring shaft is provided at the connection between the telescopic rod and the inside of the groove.

[0016] Explanation: By optimizing the structure of the injection pipe, the remediation agent can be injected into the soil from different directions, thereby achieving deep diffusion injection and improving the remediation effect.

[0017] Furthermore, the submersible pump is connected to the second pneumatic pump via a second conduit that passes through the packer. The second conduit is slidably connected to a cavity provided inside the packer. A first rubber sleeve is provided on the inner wall of the cavity, and a second rubber sleeve is provided on the outer wall of the packer. Both the first and second rubber sleeves are provided with water-absorbing resin. The bottom of the injection pipe is connected to the inside of the first and second rubber sleeves via branch pipes.

[0018] Explanation: By optimizing the internal structure of the packer, it can achieve a sealed barrier to the groundwater circulation well, thereby enabling independent operation of extraction and injection.

[0019] Furthermore, the bottom of the multiphase extraction well, the groundwater circulation well, and the auxiliary injection well are all equipped with screen pipes.

[0020] Note: The groundwater is filtered through a sieve tube and is easy to extract.

[0021] The present invention also provides an ISCO repair method, based on an ISCO repair system as described in any one of the above claims, comprising the following steps:

[0022] S1. Pollution assessment: Heavy metals and organic pollutants in the soil and groundwater of the site to be remediated are tested. Based on the detected pollution, the site to be remediated is divided into a simple soil pollution area, a simple groundwater pollution area, and a combined soil and groundwater pollution area.

[0023] S2. Remediation of simple soil contamination areas: For simple soil contamination areas, several groundwater circulation wells are set up at the pollution source location and its surroundings, and remediation agents are injected into the groundwater circulation wells for ISCO remediation.

[0024] S3. Remediation of simple groundwater contamination areas: For simple groundwater contamination areas, multiphase extraction wells are set up at the pollution source location to perform NAPL extraction. Several groundwater circulation wells are set up in the pollution plume downstream of the groundwater flow to extract groundwater below the packer. At the same time, remediation agent is injected into the part above the packer for ISCO remediation.

[0025] S4. Remediation of Soil-Groundwater Complex Pollution Zone: For soil-groundwater complex pollution zones, multiphase extraction wells are installed at the pollution source location for NAPL extraction. Several groundwater circulation wells are installed downstream along the groundwater flow to extract groundwater below the packer. At the same time, remediation agent is injected into the portion above the packer for ISCO remediation. Several auxiliary injection wells are installed at the pollution plume boundary to inject remediation agent into the auxiliary injection wells for ISCO remediation.

[0026] The repair agent comprises: 4-5% sodium persulfate as an oxidant and 2-3% sodium hydroxide as an activator, with the remainder being water.

[0027] Furthermore, the so-called simple soil pollution zone refers to a site to be remediated where at least two heavy metals or organic pollutants exceed the detection limits for Class II land use; the so-called simple groundwater pollution zone refers to a site to be remediated where at least two heavy metals or organic pollutants exceed the detection limits for Class V land use, and NAPL is present; the so-groundwater combined pollution zone is one that simultaneously meets the conditions of both the so-called simple soil pollution zone and the so-called simple groundwater pollution zone.

[0028] Note: The method is made more scientific by optimizing the classification of pollution levels.

[0029] Furthermore, in S2 to S4, the number of groundwater circulation wells is 3 to 25, and the spacing between them is 5 to 15m. In S4, the number of auxiliary injection wells is 5 to 20, and the spacing between them is 10 to 20m. The depth of the multiphase extraction wells and the groundwater circulation wells is 1 to 3m below the groundwater level, and the depth of the auxiliary injection wells is 5 to 25m.

[0030] Note: By optimizing the number of groundwater circulation wells and auxiliary injection wells, this method is applicable to the remediation of areas with different levels and areas of pollution.

[0031] Furthermore, in S2, the injection rate of the remediation agent in the groundwater circulation well is 0.1–2 L / min, the injection cycle is 8 hours intermittent for 8 hours, and it lasts for 7–48 days. In S3, the injection rate of the remediation agent in the groundwater circulation well is 0.5–20 L / min, it lasts for 7–48 days, and the groundwater extraction rate is 5–8 times the injection rate. In S4, the injection rate of the remediation agent in the groundwater circulation well is 0.5–20 L / min, the injection rate of the auxiliary injection well is 0.1–2 L / min, it lasts for 7–48 days, and the groundwater extraction rate is 5–8 times the injection rate.

[0032] Note: By optimizing and adjusting the injection speed and time, the repair process is made smoother and the repair efficiency is improved.

[0033] Furthermore, in S3 and S4, a side test is performed every 7 days. If no NAPL is present in the groundwater, NAPL extraction from the multiphase extraction well is stopped. Every 7 to 10 days, the injection pipes of 20 to 30% of the groundwater circulation wells are removed so that the groundwater circulation wells can be used as auxiliary injection wells. For S4, every 7 to 10 days, 30 to 40% of the auxiliary injection wells are reduced.

[0034] Note: By optimizing the dynamic relationship between detection and repair, the repair process is made more reasonable.

[0035] The beneficial effects of this invention are:

[0036] (1) The ISCO remediation system of the present invention provides a variety of remediation wells with different structures for various pollution situations that may exist in soil and groundwater. It can realize the extraction of NAPL and the synchronous injection of remediation agents at multiple points. In particular, after the structural optimization and adjustment of the groundwater circulation well, it can realize deep diffusion injection into the soil. At the same time, it can achieve linkage control with the packer, which can ensure extraction efficiency and accuracy, improve injection efficiency, and is easy to operate and easy to recover. It has important practical significance for the ISCO remediation of soil and groundwater.

[0037] (2) The ISCO remediation method of the present invention provides a variety of remediation schemes for various pollution situations that may exist in soil and groundwater. It revolves around the groundwater circulation well, reduces the concentration of pollutants, and then supplements it with the injection of chemical oxidizing agents. Through subsequent dynamic adjustments, it achieves the purpose of shrinking the boundary of the pollution plume, so as to achieve good remediation effect and remediation efficiency in both the short and long term. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the well location layout of S2 in Embodiment 4 of the present invention;

[0039] Figure 2 This is a schematic diagram of the well location layout in Embodiment 4 of the present invention;

[0040] Figure 3 This is a schematic diagram of the well location layout in Embodiment 4 of the present invention;

[0041] Figure 4 This is a schematic diagram of the connection structure between the multiphase extraction well and the first surface system;

[0042] Figure 5 This is a schematic diagram of the connection structure between the groundwater circulation well and the second surface system;

[0043] Figure 6 This is a schematic diagram of the connection structure between the auxiliary injection well and the third surface system;

[0044] Figure 7 This is a schematic diagram of the internal structure of a groundwater circulation well;

[0045] Figure 8 This is a schematic diagram of the connection between the bottom of the injection tube and the packer;

[0046] Figure 9 This is a cross-sectional view of the connection between the bottom of the injection tube and the packer;

[0047] Figure 10 This is a top view of the interior of a groundwater circulation well;

[0048] Figure 11This is a schematic diagram of the bottom structure of the injection tube before use;

[0049] Figure 12 This is a schematic diagram of the bottom structure of the injection tube after use.

[0050] Among them, 1-multiphase extraction well, 2-groundwater circulation well, 21-opening, 22-screen pipe, 3-auxiliary injection well, 4-first surface system, 41-first pneumatic pump, 42-gas-liquid separation tank, 43-oil-gas separation tank, 44-storage tank, 45-first conduit, 5-second surface system, 51-second pneumatic pump, 52-water tank, 53-activated carbon adsorption box, 54-first reagent tank, 6-third surface system, 61-third pneumatic pump, 62-second reagent tank, 63-temporary storage tank, 64-third conduit, 7-packer, 71-submersible pump, 72-second conduit, 73-cavity, 74-first rubber sleeve, 75-second rubber sleeve, 8-injection pipe, 81-groove, 82-compression pipe, 83-plug, 84-telescopic rod, 85-breaking shovel, 86-guide pipe, 87-spring shaft, 88-branch pipe. Detailed Implementation

[0051] Example 1

[0052] like Figures 4-6 As shown, an ISCO remediation system includes a multiphase extraction well 1, a groundwater circulation well 2, and an auxiliary injection well 3. Screen pipes 22 are provided at the bottom of the multiphase extraction well 1, the groundwater circulation well 2, and the auxiliary injection well 3.

[0053] like Figures 4-6 As shown, the multiphase extraction well 1 is connected to the first surface system 4, the groundwater circulation well 2 is connected to the second surface system 5, and the auxiliary injection well 3 is connected to the third surface system 6. The first surface system 4 includes a first pneumatic pump 41, a gas-liquid separator 42, an oil-gas separator 43, and a storage tank 44 connected in sequence. The gas-liquid separator 42 and the oil-gas separator 43 are both commercially available products capable of separating NAPL. The first pneumatic pump 41 is connected to the inside of the multiphase extraction well 1 through a first conduit 45. The second surface system 5 includes two second gas... The system includes a pneumatic pump 51, a water tank 52 and an activated carbon adsorption tank 53 connected sequentially to one of the second pneumatic pumps 51, and a first reagent tank 54 connected sequentially to another second pneumatic pump 51. The activated carbon adsorption tank 53 is a commercially available activated carbon adsorption tank. The third surface system 6 includes a third pneumatic pump 61, a second reagent tank 62, and a temporary storage tank 63 connected sequentially. The third pneumatic pump 61 is connected to the auxiliary injection well 3 through a third conduit 64. The first pneumatic pump 41, the second pneumatic pump 51, and the third pneumatic pump 61 are all commercially available pneumatic pumps.

[0054] like Figures 7-10As shown, a packer 7 is provided inside the groundwater circulation well 2. A submersible pump 71 is provided below the packer 7. An injection pipe 8 is also provided inside the groundwater circulation well 2. The bottom of the injection pipe 8 is threaded and sealed to the middle of the upper surface of the packer 7. Three grooves 81 are provided circumferentially at equal intervals on the bottom side wall of the injection pipe 8. A compression pipe 82 is provided at the bottom of the groove 81. A plug 83 is provided at the front end of the compression pipe 82 and extends out of the groove 81. The rear end of the compression pipe 82 is connected to and sealed to the injection pipe 8 inside the groove 81. A telescopic rod 84 is provided inside the groove 81. The end of the telescopic rod 84 is connected to the plug 83 through a shovel 85. A guide pipe 86 is fixed in the middle of one side of the shovel 85. A corresponding opening 21 is provided on the side wall of the well barrel of the groundwater circulation well 2 at the position pointed to by each guide pipe 86. A spring shaft 87 is provided at the connection between the telescopic rod 84 and the inside of the groove 81.

[0055] like Figures 7-10 As shown, the submersible pump 71 is connected to the second pneumatic pump 51 via a second conduit 72 that passes through the packer 7. The second conduit 72 is slidably connected to the cavity 73 provided inside the packer 7. The inner wall of the cavity 73 is provided with a first rubber sleeve 74, and the outer wall of the packer 7 is provided with a second rubber sleeve 75. Both the first rubber sleeve 74 and the second rubber sleeve 75 are provided with water-absorbing resin. The bottom of the injection pipe 8 is connected to the inside of the first rubber sleeve 74 and the second rubber sleeve 75 via a branch pipe 88.

[0056] Example 2

[0057] The difference between this embodiment and Embodiment 1 is that:

[0058] There are two grooves 81, and correspondingly, there are two compression tubes 82 and two telescopic rods 84.

[0059] Example 3

[0060] The difference between this embodiment and Embodiment 1 is that:

[0061] There are 4 grooves 81, and correspondingly there are 4 compression tubes 82, 4 telescopic rods 84, etc.

[0062] Example 4

[0063] This embodiment provides an ISCO repair method based on an ISCO repair system in Embodiment 1, including the following steps:

[0064] S1. Pollution assessment: Heavy metals and organic pollutants in the soil and groundwater of the site to be remediated are tested. Based on the detected pollution, the site to be remediated is divided into a simple soil pollution area, a simple groundwater pollution area, and a combined soil and groundwater pollution area.

[0065] A simple soil contamination zone is defined as a site to be remediated where at least two heavy metals or organic pollutants exceed the detection limits for Class II land use. A simple groundwater contamination zone is defined as a site to be remediated where at least two heavy metals or organic pollutants exceed the detection limits for Class V land use and NAPL is present. A combined soil and groundwater contamination zone is defined as a site that simultaneously meets the conditions for both simple soil contamination zone and simple groundwater contamination zone.

[0066] S2. Remediation of simple soil contamination areas: such as... Figure 1 As shown, for areas with simple soil pollution, seven groundwater circulation wells 2 are set up at and around the pollution source. ISCO remediation is carried out by injecting remediation agent into the groundwater circulation wells 2. The injection rate of the remediation agent in the groundwater circulation wells 2 is 1L / min, and the injection cycle is every 8 hours with an 8-hour interval, which lasts for 14 days.

[0067] S3. Remediation of areas with simple groundwater contamination: such as... Figure 2 As shown, for a simple groundwater contaminated area, a multiphase extraction well 1 is set up at the pollution source location for NAPL extraction. Six groundwater circulation wells 2 are set up in the pollution plume downstream of the groundwater flow to extract the groundwater below the packer 7. At the same time, remediation agent is injected into the part above the packer 7 for ISCO remediation. The injection rate of the remediation agent in the groundwater circulation wells 2 is 4L / min, which lasts for 14 days. The groundwater extraction rate is 6 times the injection rate.

[0068] S4. Remediation of areas with combined soil and groundwater pollution: such as... Figure 3 As shown, for the soil-groundwater combined pollution zone, a multiphase extraction well 1 is set up at the pollution source location for NAPL extraction. Six groundwater circulation wells 2 are set up downstream along the groundwater flow to extract the groundwater below the packer 7. At the same time, remediation agent is injected into the part above the packer 7 for ISCO remediation. Five auxiliary injection wells 3 are set up at the pollution plume boundary to inject remediation agent into the auxiliary injection wells 3 for ISCO remediation. The spacing between the wells is 16m. The injection rate of the remediation agent in the groundwater circulation wells 2 is 3L / min, and the injection rate in the auxiliary injection wells 3 is 0.9L / min. This is carried out for 20 days. The groundwater extraction rate is 7 times the injection rate.

[0069] In S2 to S4, the spacing between the groundwater circulation wells 2 is 10m, the depth of both the multiphase extraction well 1 and the groundwater circulation well 2 is more than 2m below the groundwater level, and the depth of the auxiliary injection well 3 is 15m.

[0070] The repair agent consists of: 4.5% sodium persulfate as an oxidant and 2.5% sodium hydroxide as an activator, with the remainder being water;

[0071] In S3 and S4, one side is tested every 7 days. If no NAPL is present in the groundwater, NAPL extraction from the multiphase extraction well 1 is stopped. Every 8 days, 25% of the injection pipes 8 of the groundwater circulation wells 2 are removed so that the groundwater circulation wells 2 can be used as auxiliary injection wells 3. For S4, 35% of the auxiliary injection wells 3 are reduced every 8 days.

[0072] Furthermore, we will further explain the specific working principle of the injection tube 8 and packer 7 of the present invention in conjunction with the method of the present invention.

[0073] During S2 to S4, groundwater circulation well 2 needs to extract groundwater and inject remediation agent. Therefore, to avoid mutual interference, groundwater circulation well 2 consists of two closed well sections: the upper section is the remediation agent injection section and the lower section is the groundwater extraction section. During the remediation process, groundwater is extracted from groundwater circulation well 2 to surface water tank 52, and then adsorbed and discharged or reinjected into the formation through activated carbon adsorption tank 53.

[0074] Then, the repair agent inside the first agent tank 54 is injected into the soil through the second pneumatic pump 51. Before that, it needs to be pressurized. The groundwater treated above is injected into the injection pipe 8. After the groundwater enters the compression pipe 82, the pressure is gradually increased. Under the pressure, the compression pipe 82 gradually extends, driving the soil breaking shovel 85 to extend from the opening 21 into the soil. At the same time, under the action of the telescopic rod 84, the soil breaking shovel 85 is kept as horizontal as possible.

[0075] At the same time, some of the pressurized groundwater enters the space inside the packer 7. When it enters the first rubber sleeve 74 and the second rubber sleeve 75 through the branch pipe 88, it absorbs water and expands through the water-absorbing resin, causing the first rubber sleeve 74 to squeeze the second conduit 72 to complete the seal at the cavity 73. At the same time, the second rubber sleeve 75 squeezes the inner wall of the groundwater circulation well 2 to complete the sealing and isolation of the groundwater circulation well 2.

[0076] Until the compression tube 82 extends to its maximum length, such as Figure 11 The state shown becomes Figure 12 As shown in the diagram, the soil-breaking shovel 85 moves to its furthest position, which in turn drives each guide pipe 86 to penetrate into the soil in each direction of the groundwater circulation well 2. The remediation agent can be injected into the guide pipe 86 to achieve diffusion injection of the remediation agent.

[0077] After injection is completed, injection pipe 8 needs to be removed. Pulling injection pipe 8 will cause it to reset the soil breaking shovel 85. At the same time, the spring shaft 87 at the rear end of telescopic rod 84 can be used to help it pass smoothly through opening 21. Rotating injection pipe 8 in the opposite direction will cause it to separate from packer 7 by thread rotation. Then injection pipe 8 can be removed. At this time, packer 7 will always remain in the well. If it is necessary to continue injecting repair agent, it can be injected directly into the well. The injected repair agent will directly enter the soil above packer 7.

[0078] If you want to remove the packer 7, simply extract the injection tube 8 without rotating it.

[0079] Example 5

[0080] The difference between this embodiment and embodiment 4 is that:

[0081] In S2, the injection rate of the remediation agent in the groundwater circulation well 2 is 2L / min, with an injection cycle of 8 hours followed by an 8-hour interval, lasting for 7 days.

[0082] Example 6

[0083] The difference between this embodiment and embodiment 4 is that:

[0084] In S2, the injection rate of the remediation agent in the groundwater circulation well 2 is 0.1 L / min, with an injection cycle of 8 hours followed by an 8-hour interval, lasting for 48 days.

[0085] Example 7

[0086] The difference between this embodiment and embodiment 4 is that:

[0087] In S3, the injection rate of the remediation agent in groundwater circulation well 2 is 20 L / min, which lasts for 7 days, and the groundwater extraction rate is 5 times the injection rate.

[0088] Example 8

[0089] The difference between this embodiment and embodiment 4 is that:

[0090] In S3, the injection rate of the remediation agent in groundwater circulation well 2 is 0.5 L / min, which lasts for 48 days. The groundwater extraction rate is 8 times the injection rate.

[0091] Example 9

[0092] The difference between this embodiment and embodiment 4 is that:

[0093] In S4, there are 5 auxiliary injection wells 3, with a spacing of 20m. The injection rate of the remediation agent in the groundwater circulation well 2 is 20L / min, and the injection rate of the auxiliary injection well 3 is 2L / min, which lasts for 7 days. The groundwater extraction rate is 5 times the injection rate.

[0094] Example 10

[0095] The difference between this embodiment and embodiment 4 is that:

[0096] In S4, there are 20 auxiliary injection wells 3, with a spacing of 10m. The injection rate of the remediation agent in the groundwater circulation well 2 is 0.5L / min, and the injection rate of the auxiliary injection well 3 is 0.1L / min, which lasts for 48 days. The groundwater extraction rate is 8 times the injection rate.

[0097] Example 11

[0098] The difference between this embodiment and embodiment 4 is that:

[0099] In S2 to S4, there are 25 groundwater circulation wells 2, with a spacing of 5m. The depth of both multiphase extraction well 1 and groundwater circulation well 2 exceeds 1m below the groundwater level, and the depth of auxiliary injection well 3 is 5m.

[0100] Example 12

[0101] The difference between this embodiment and embodiment 4 is that:

[0102] In S2 to S4, there are 3 groundwater circulation wells 2, with a spacing of 15m. The depth of both multiphase extraction well 1 and groundwater circulation well 2 exceeds 3m below the groundwater level, and the depth of auxiliary injection well 3 is 25m.

[0103] Example 13

[0104] The difference between this embodiment and embodiment 4 is that:

[0105] The repair agent consists of: 4% sodium persulfate as an oxidant and 2% sodium hydroxide as an activator, with the remainder being water.

[0106] Example 14

[0107] The difference between this embodiment and embodiment 4 is that:

[0108] The repair agent consists of: 5% sodium persulfate as an oxidant and 3% sodium hydroxide as an activator, with the remainder being water.

[0109] Example 15

[0110] The difference between this embodiment and embodiment 4 is that:

[0111] In S3 and S4, one side is tested every 7 days. If no NAPL is present in the groundwater, NAPL extraction from the multiphase extraction well 1 is stopped. Every 7 days, 20% of the injection pipes 8 of the groundwater circulation wells 2 are removed so that the groundwater circulation wells 2 can be used as auxiliary injection wells 3. For S4, 30% of the auxiliary injection wells 3 are reduced every 7 days.

[0112] Example 16

[0113] The difference between this embodiment and embodiment 4 is that:

[0114] In S3 and S4, one side is tested every 7 days. If no NAPL is present in the groundwater, NAPL extraction from the multiphase extraction well 1 is stopped. Every 10 days, 30% of the injection pipes 8 of the groundwater circulation wells 2 are removed so that the groundwater circulation wells 2 can be used as auxiliary injection wells 3. For S4, 40% of the auxiliary injection wells 3 are reduced every 10 days.

[0115] Experimental Example

[0116] Following the method in Example 4 and the apparatus in Example 1, we remediated the soil and groundwater of the contaminated site in a zoned and phased manner. First, we prioritized the remediation of the pollution source or the location with high concentration of pollution by using the multiphase extraction well 1 to extract NAPL and recover the pollutants, removing a large amount of NAPL. In other medium and low concentration areas, we set up a remediation system with groundwater circulation well 2 and auxiliary injection well 3 to cover the main pollution range, and then continued to operate and improve it. For the pollution extension area (dissolved phase pollution plume) within the remediation area, we carried out chemical oxidation remediation to gradually reduce the pollution range and complete the remediation work. We used the formed groundwater circulation flow field to promote the contact reaction between the reagent and the pollutants in the groundwater.

[0117] The plant area soil and groundwater pollution risk management and remediation project has a total of 4 pollution sources and a total of 31 wells, including 4 multiphase extraction wells 1, 19 groundwater circulation wells 2, and 8 auxiliary injection wells 3. Among them, multiphase extraction wells 1, 7 groundwater circulation wells 2 and 3 auxiliary injection wells 3 also serve as monitoring wells.

[0118] The soil on the east side of the remediation area is mainly silty soil at depths of 0-1 meters and 12 meters below the surface; the soil on the south side is mainly silty soil at depths of 3-4 meters and 12 meters below the surface; the soil on the west side is mainly silty soil at depths of 1-2 meters and 14 meters below the surface; and the soil on the north side shows a clear alternation between shallow sandy soil and silty soil, with silty soil being the dominant soil at depths of 14 meters below the surface.

[0119] The stratigraphic distribution is roughly consistent with the geological exploration results during the field investigation phase. The deep silty soil appears about 12 meters below the surface on the east side of the remediation area and about 14 meters below the surface on the west side of the remediation area, indicating that the silty layer is inclined from east to west.

[0120] Multiphase extraction well 1 uses HDPE material and has a diameter of 63mm. The deep well reaches the bottom of the aquifer, with a well depth of 21 meters and a screening range of 15 (or 16.5 meters) to 21 meters; the shallow well depth is mainly to cover known high-concentration pollution locations, including adjacent soil, with a well depth of 9 meters or 12 meters and a screening range of 3 to 9 meters or 7.5 to 12 meters.

[0121] On-site construction process:

[0122] ① Drilling: Drill hole diameter 150mm;

[0123] ② Well construction: Well depth 21 meters;

[0124] Well casing: HDPE material, 63mm diameter, connected by hot welding.

[0125] Well screen: HDPE material, 63mm diameter, see Table 2-7 for details of screen opening, 0.6mm screen gap width, connected to well pipe by hot welding.

[0126] Manhole cover: Special manhole head, 63mm in diameter.

[0127] Manhole cover: HDPE material, 63mm diameter, connected by heat welding.

[0128] Filter media: Clean, impurity-free, uniformly sized quartz sand with a particle size of approximately 1.0mm to 2.0mm.

[0129] Bentonite: Highly expansive granular bentonite with a diameter of 11–14 mm.

[0130] Circular seal and surface seal: diatomaceous earth slurry and silicate No. 1 cement.

[0131] After the well was installed, a well-washing operation was carried out using the air-lift method.

[0132] The groundwater circulation well No. 2 is constructed to a depth of 20 meters, with a screening range of 14 to 20 meters and a diameter of 55 cm.

[0133] ① Drilling: 2 groundwater circulation wells with a borehole diameter of 55cm.

[0134] ② Well installation: Well casing: HDPE material, connected by hot welding.

[0135] Well screen: HDPE material, screen gap width 0.6mm, connected to well pipe by hot welding.

[0136] Manhole cover: Special manhole head.

[0137] Manhole cover: HDPE material, threaded connector.

[0138] Filter media: Clean, impurity-free, uniformly sized quartz sand with a particle size of approximately 1.0mm to 2.0mm.

[0139] Bentonite: Highly expansive granular bentonite with a diameter of 11–14 mm.

[0140] Circular seal and surface seal: diatomaceous earth slurry and silicate No. 1 cement.

[0141] After the well was installed, a well-washing operation was carried out using the air-lift method.

[0142] The well casing for auxiliary injection well 3 is made of HDPE material, with a diameter of 11cm, and is connected by hot welding.

[0143] Well screen: HDPE material, 11cm diameter, 0.6mm screen slot width, connected to the well pipe by hot welding.

[0144] Well top cover: Special well head, 11cm in diameter.

[0145] Manhole cover: HDPE material, 11cm diameter, connected by heat welding.

[0146] Filter media: Clean, impurity-free, uniformly sized quartz sand with a particle size of approximately 1.0–2.0 mm.

[0147] Bentonite: Highly expansive granular bentonite with a diameter of 11–14 mm.

[0148] Circular seal and surface seal: diatomaceous earth slurry and silicate No. 1 cement.

[0149] After the well was installed, a well-washing operation was carried out using the air-lift method.

[0150] Every 8 days, 25% of the injection pipes 8 of the groundwater circulation wells 2 are removed. The number of wells is rounded down from 19, reducing by 4 for the first time, leaving 15. The number of wells is reduced by 3 for the second time, and so on, so that the groundwater circulation wells 2 can be used as auxiliary injection wells 3. Every 8 days, 35% of the auxiliary injection wells 3 are removed. The number of wells is rounded down from 8, reducing by 2 for the first time, plus the 4 wells converted from groundwater circulation wells 2, leaving 10 wells. The number of wells is reduced by 3 for the second time, plus the 3 wells converted from groundwater circulation wells 2, leaving 10 wells, and so on.

[0151] Repair results:

[0152] (1) VOCs

[0153] First, for wells with high concentrations of pollutants and containing oil, high-concentration groundwater and pure-phase substances were extracted. According to monitoring data, the concentration of the target pollutant, 1,2-dichloroethane, fluctuated and decreased. Then, groundwater circulation was maintained intermittently; the circulating flow field accelerated the removal of pollutants. Next, the groundwater pumping and injection circulation phase began, employing auxiliary chemical injection to enhance remediation. With the addition of chemicals, the concentration of the target pollutant, 1,2-dichloroethane, decreased significantly, a large amount of pollutant was removed, and the contaminated area gradually shrank.

[0154] Monitoring data indicated that the initial remediation effect had been achieved. However, monitoring data also revealed that some soil samples on the northeastern side of the remediation area still exceeded the standards. Subsequent remediation was carried out in this area, employing a combination of pumping and circulating remediation methods with chemical injection to enhance the process. Subsequent monitoring results showed that soil pollutant levels were below the remediation target.

[0155] Until the repair is completed, based on the test results, it is preliminarily determined that the repair goal has been achieved.

[0156] (2) Basic water quality (pH, EC, ORP)

[0157] With the addition of the reagent, pH, EC, and ORP all increased. Before the remediation activity, some wells had negative ORP values, indicating that they were in a reducing state and contained certain contaminants. As the remediation activity concluded, pH and EC gradually returned to their pre-remediation states.

[0158] (3) PID concentration

[0159] The PID dropped significantly in the early stage of the remediation system operation and slowed down significantly in the later stage, indicating that DPE has a certain effect on the remediation of this site and can remove some pollutants. However, as a new phase equilibrium is established, the number of extracted pollutants decreases.

Claims

1. An ISCO repair system, characterized in that, It includes a multiphase extraction well (1), a groundwater circulation well (2), and an auxiliary injection well (3); The multiphase extraction well (1) is connected to the first surface system (4), the groundwater circulation well (2) is connected to the second surface system (5), and the auxiliary injection well (3) is connected to the third surface system (6). The first surface system (4) includes a first pneumatic pump (41), a gas-liquid separation tank (42), an oil-gas separation tank (43), and a storage tank (44) connected in sequence. The second surface system (5) includes two second pneumatic pumps (51), a water tank (52) and an activated carbon adsorption tank (53) connected in sequence to one of the second pneumatic pumps (51), and a first reagent tank (54) connected in sequence to the other second pneumatic pump (51). The third surface system (6) includes a third pneumatic pump (61), a second medicine tank (62), and a temporary storage tank (63) connected in sequence. The groundwater circulation well (2) is equipped with a packer (7), and a submersible pump (71) is provided below the packer (7). The groundwater circulation well (2) is also equipped with an injection pipe (8). The bottom of the injection pipe (8) is threaded and sealed to the middle of the upper surface of the packer (7). The bottom side wall of the injection pipe (8) is provided with several grooves (81) at equal intervals in the circumferential direction. The bottom of the groove (81) is provided with a compression pipe (82). The front end of the compression pipe (82) is provided with a plug (83) and extends out of the groove (81). The rear end of the compression pipe (82) is connected to the injection pipe (8) inside the groove (81) and sealed. The inside of the groove (81) is provided with a telescopic rod (84). The end of the telescopic rod (84) is connected to the plug (83) through a shovel (85). The middle of one side of the shovel (85) is fixed with a guide pipe (86). The well wall of the groundwater circulation well (2) corresponding to the position pointed to by each guide pipe (86) is provided with a corresponding opening (21). The connection between the telescopic rod (84) and the inside of the groove (81) is provided with a spring shaft (87). The submersible pump (71) is connected to the second pneumatic pump (51) via a second conduit (72) that passes through the packer (7). The second conduit (72) is slidably connected to a cavity (73) provided inside the packer (7). A first rubber sleeve (74) is provided on the inner wall of the cavity (73), and a second rubber sleeve (75) is provided on the outer wall of the packer (7). Water-absorbing resin is provided inside both the first rubber sleeve (74) and the second rubber sleeve (75). The bottom of the injection pipe (8) is connected to the inside of the first rubber sleeve (74) and the second rubber sleeve (75) via a branch pipe (88).

2. The ISCO repair system according to claim 1, characterized in that, The first pneumatic pump (41) is connected to the interior of the multiphase extraction well (1) through the first conduit, and the third pneumatic pump (61) is connected to the interior of the auxiliary injection well (3) through the third conduit.

3. The ISCO repair system according to claim 1, characterized in that, The bottom of the multiphase extraction well (1), the groundwater circulation well (2), and the auxiliary injection well (3) are all equipped with screen pipes (22).

4. An ISCO repair method, based on the ISCO repair system according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Pollution assessment: Heavy metals and organic pollutants in the soil and groundwater of the site to be remediated are tested. Based on the detected pollution, the site to be remediated is divided into a simple soil pollution area, a simple groundwater pollution area, and a combined soil and groundwater pollution area. S2. Remediation of simple soil pollution areas: For simple soil pollution areas, several groundwater circulation wells (2) are set up at the pollution source location and its surroundings, and remediation agents are injected into the groundwater circulation wells (2) for ISCO remediation; S3. Remediation of simple groundwater contamination areas: For simple groundwater contamination areas, the multiphase extraction well (1) is set up at the pollution source location to perform NAPL extraction. Several groundwater circulation wells (2) are set up in the pollution plume downstream of the groundwater flow to extract the groundwater below the packer (7). At the same time, remediation agent is injected into the part above the packer (7) for ISCO remediation. S4. Remediation of Soil-Groundwater Complex Pollution Zone: For soil-groundwater complex pollution zone, the multiphase extraction well (1) is set up at the pollution source location for NAPL extraction. Several groundwater circulation wells (2) are set up downstream along the groundwater flow to extract groundwater below the packer (7). At the same time, remediation agent is injected into the part above the packer (7) for ISCO remediation. Several auxiliary injection wells (3) are set up at the pollution plume boundary and remediation agent is injected into the auxiliary injection wells (3) for ISCO remediation. The repair agent comprises: 4-5% sodium persulfate as an oxidant and 2-3% sodium hydroxide as an activator, with the remainder being water.

5. The ISCO repair method according to claim 4, characterized in that, The term "simple soil contamination zone" refers to a site to be remediated where at least two heavy metals or organic pollutants exceed the detection limits for Class II land use. The term "simple groundwater contamination zone" refers to a site to be remediated where at least two heavy metals or organic pollutants exceed the detection limits for Class V land use, and NAPL is present. The term "combined soil and groundwater contamination zone" refers to a site that simultaneously meets the conditions for both simple soil contamination zone and simple groundwater contamination zone.

6. The ISCO repair method according to claim 4, characterized in that, In S2~S4, the number of groundwater circulation wells (2) is 3~25, and the spacing between them is 5~15m. In S4, the number of auxiliary injection wells (3) is 5~20, and the spacing between them is 10~20m. The depth of the multiphase extraction wells (1) and the groundwater circulation wells (2) is 1~3m below the groundwater level, and the depth of the auxiliary injection wells (3) is 5~25m.

7. The ISCO repair method according to claim 6, characterized in that, In S2, the injection rate of the remediation agent in the groundwater circulation well (2) is 0.1~2L / min, the injection cycle is 8h interval every 8h, and it lasts for 7~48 days. In S3, the injection rate of the remediation agent in the groundwater circulation well (2) is 0.5~20L / min, it lasts for 7~48 days, and the groundwater extraction rate is 5~8 times the injection rate. In S4, the injection rate of the remediation agent in the groundwater circulation well (2) is 0.5~20L / min, the injection rate of the auxiliary injection well (3) is 0.1~2L / min, it lasts for 7~48 days, and the groundwater extraction rate is 5~8 times the injection rate.

8. The ISCO repair method according to claim 7, characterized in that, In S3 and S4, one side is tested every 7 days. If there is no NAPL in the groundwater, the NAPL extraction of the multiphase extraction well (1) is stopped. Every 7 to 10 days, the injection pipe (8) of 20 to 30% of the groundwater circulation wells (2) is removed so that the groundwater circulation wells (2) can be used as auxiliary injection wells (3). For S4, every 7 to 10 days, the number of auxiliary injection wells (3) is reduced by 30 to 40%.

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