In-situ leaching remediation process for organochlorine pesticide contaminated soil

Abstract

The application discloses an in-situ leaching remediation process for organochlorine pesticide contaminated soil, comprising the following steps: S1, center well site layout, S2, annular well site layout, S3, step-by-step leaching: S3-1, first-stage leaching, S3-2, second-stage leaching, S3-3, third-stage leaching, S3-4, fourth-stage leaching, the application divides the injection well and the extraction well points in the organochlorine pesticide contaminated soil area, and then forms a step-by-step layered leaching mode from inside to outside, and the injection well and the extraction well can be quickly switched, so that the leaching efficiency is greatly improved, the leaching liquid is conveniently recovered, the work efficiency is improved, the leaching mode is more scientific and reasonable, the shape area of the well site is optimized and adjusted, a complete injection and extraction mode is formed, and good leaching effect can be achieved on the organochlorine pesticide contaminated soil.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic chlorine contaminated soil remediation, in particular to an in-situ leaching remediation process for organic chlorine pesticide contaminated soil. BACKGROUND

[0002] Organic chlorine pesticide pollution is caused by polychlorinated organic synthetic insecticides. The main varieties of organic chlorine pesticides are DDT, BHC, etc. Because of its stable chemical properties and difficult to decompose, it can cause serious environmental pollution. The commonly used organic chlorine pesticides have the following characteristics: low vapor pressure, low volatility, so it disappears slowly after use; the chlorobenzene structure is relatively stable and is not easily degraded by the enzyme system of the organism, so the organic chlorine pesticide molecules accumulated in the organism and plant body disappear slowly; some organic chlorine pesticides can be suspended on the water surface in water, and can evaporate with water molecules on the air-water interface, and DDT molecules can be detected in areas where DDT has not been used, which is related to this evaporation; generally, they are hydrophobic and lipophilic compounds, and the solubility in water is mostly less than 1 ppm, which makes it impossible for organic chlorine pesticides to seep and lose in large quantities in the soil layer, but they can be more adsorbed on soil particles, especially in soil with high organic matter content. Therefore, the retention period of organic chlorine pesticides in soil can be as long as several years; the action of soil microorganisms on these pesticides is mostly to reduce or oxidize them into similar derivatives, and these products also have residual toxicity problems like their parent compounds.

[0003] Organic chlorine pesticides enter the human and animal body through the food chain and can accumulate in the heart, liver, kidney and other tissues. Because these pesticides have high lipophilicity, they accumulate most in fat. The accumulated residual pesticides can also be excreted through breast milk or transferred to egg, egg and other tissues, affecting the offspring. Therefore, countries have strict control on the residual organic chlorine pesticides in food. The soil in China, especially agricultural soil, is generally contaminated by organic chlorine pesticides, which needs further monitoring and management.

[0004] At present, the in-situ remediation methods for organic chlorine pesticide contaminated soil include biological remediation, chemical leaching, soil improvement, water and soil conservation, etc. However, a single remediation method often has poor remediation effect. SUMMARY

[0005] In view of the above problems, the present application provides an in-situ leaching remediation process for organic chlorine pesticide contaminated soil.

[0006] The technical scheme of the present application is as follows:

[0007] An in-situ leaching remediation process for organic chlorine pesticide contaminated soil, comprising the following steps:

[0008] S1, center well layout: investigate the boundary and depth of the organic chlorine pesticide contaminated soil area by ground penetrating radar, determine the area and depth of the organic chlorine pesticide contaminated soil area, determine the center point of the organic chlorine pesticide contaminated soil area, and arrange the center point well at the center point, and arrange three center triangular wells around the center point well, so that the three center triangular wells form an equilateral triangle, and the center point well is located at the center of the equilateral triangle;

[0009] S2, annular well layout: six inner ring wells are arranged around the outside of the center triangular well to form a circular ring, and six outer ring wells are arranged around the outside of the inner ring well to form a circular ring, and the center of the circular ring formed by the six inner ring wells and the circular ring formed by the six outer ring wells falls on the center point well;

[0010] S3, step-by-step leaching: by combining the center point well, the center triangular well, the six inner ring wells and the six outer ring wells from the inside to the outside, step-by-step injection and extraction of leaching liquid is carried out to complete primary leaching, secondary leaching, tertiary leaching and quaternary leaching.

[0011] Further, the specific steps of the step-by-step leaching are as follows:

[0012] S3-1, primary leaching: the center point well is set as the leaching liquid injection point, the three center triangular wells are set as the extraction points, and the injection and extraction of leaching liquid are carried out respectively, the injection speed of the injection point is 0.5-1 m 3 / h, a water pump is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 3-5 days;

[0013] S3-2, secondary leaching: the injection point in the primary leaching is stopped, the three center triangular wells are set as new injection points, and the six inner ring wells are set as new extraction points, and the injection and extraction of leaching liquid are carried out respectively, the injection speed of the injection point is 0.5-1.5 m 3 / h, a water pump is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 5-10 days;

[0014] S3-3, tertiary leaching: the injection point in the secondary leaching is stopped, and the three non-adjacent inner ring wells of the six inner ring wells are set as new injection points, the remaining three inner ring wells are stopped, and the six outer ring wells are set as new extraction points, and the injection and extraction of leaching liquid are carried out respectively, the injection speed of the injection point is 1-1.5 m 3 / h, a water pump is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 5-7 days, then the three injection points are stopped, the remaining three inner ring wells are set as new extraction points, and the injection and extraction of leaching liquid are continued, the injection speed of the injection point is 1-1.5 m 3 / h, water pump is set in the extraction point to keep the water level below the original water level, and lasts for 5-7 days;

[0015] S3-4, fourth stage leaching: the injection point in the third stage leaching is stopped, the extraction point continues to work to keep the water level below the original water level, and lasts for 2-3 days, then the center point well position, the center triangle well position and the inner ring well position are all used as injection points, and the leaching liquid is sprayed on the surface of the organochlorine pesticide contaminated soil area inside the circular ring surrounded by the inner ring well position, the injection, spraying and extraction of the leaching liquid are carried out, the injection speed of the injection point is 0.5-2.5 m 3 / h, the spraying amount is 0.3-0.7 m 3 / h, water pump is set in the extraction point to keep the water level below the original water level, and lasts for 3-5 days.

[0016] Further, the area of the equilateral triangle surrounded by the three center triangle well positions in the step S1 is 0.6-0.8 times the area of the triangle surrounded by the non-adjacent three inner ring well positions in the six inner ring well positions, and the area of the circular ring surrounded by the six inner ring well positions in the step S2 is 0.6-0.8 times the area of the circular ring surrounded by the six outer ring well positions.

[0017] Description: By optimizing and adjusting the relationship between the area of the equilateral triangle surrounded by the center triangle well positions and the area of the triangle surrounded by the non-adjacent three inner ring well positions in the inner ring well positions, the distance between the injection well and the extraction well in the second stage leaching is controlled, and the leaching effect is optimized while the recovery of the leaching liquid is ensured; by optimizing and adjusting the relationship between the area of the circular ring surrounded by the six inner ring well positions and the area of the circular ring surrounded by the six outer ring well positions, the distance between the injection well and the extraction well in the third stage leaching is controlled, and the leaching effect is optimized while the recovery of the leaching liquid is ensured.

[0018] Further, the leaching liquid injected by the injection point in the step S3 is Trition X-100 or TWEEN80, and the leaching liquid used for spraying on the surface of the organochlorine pesticide contaminated soil area inside the circular ring surrounded by the inner ring well position in the step S3-4 is hydroxypropyl β-cyclodextrin or carboxymethyl-β-cyclodextrin.

[0019] Description: By selecting the type of injected eluent and the type of sprayed eluent, the effect of the leaching is further improved. Trition X-100 or TWEEN80 is used for injection leaching. Non-ionic surfactants or anionic surfactants each have their advantages. Non-ionic surfactants have a lower critical micelle concentration and stronger solubilization and encapsulation ability for organic pollutants. The selection can be made according to the needs. Hydroxypropyl beta cyclodextrin or carboxymethyl-beta-cyclodextrin has the characteristics of hydrophilic outer edge and hydrophobic inner cavity, and can better adapt to organic chlorine pesticides in water phase. The solubilization mechanism mainly includes the following steps: the organic chlorine pesticides are wrapped and embedded in the structure of the cavity inner shell of beta cyclodextrin, and then the organic chlorine pesticides in the soil are captured to improve the removal rate of organic chlorine pesticides. It is more suitable for large-area spraying leaching. The two leaching methods are combined as the fourth-stage leaching to achieve deep leaching.

[0020] Further, the injection speed of the center point well site in the step S3-4 is 2-2.5 m 3 / h, the injection speed of the center triangle well site is 1-1.5 m 3 / h, and the injection speed of the inner ring well site is 0.5-1 m 3 / h.

[0021] Description: By optimizing the injection speed of each different well site in step S3-4, it is ensured that the injection amount is larger as it is closer to the center, so that a flow pattern from inside to outside is formed in the whole leaching system, the leaching area is improved, and finally the leaching liquid is recovered.

[0022] Further, a combined well shaft capable of switching between injection mode and extraction mode is arranged in each well site. A main well shaft is arranged in the combined well shaft. The outer wall of the main well shaft is filled with gravel. A stabilizing block is arranged at the bottom of the main well shaft. An extension well shaft is arranged at the bottom of the stabilizing block. A threaded hole is arranged in the middle of the stabilizing block. A hollow threaded rod is threadedly connected to the inside of the threaded hole. A water pump is arranged at the bottom of the threaded rod. A plurality of detachably connected sleeves are arranged at the top of the threaded rod. The uppermost one of the sleeves extends out of the main well shaft, and the sleeve is fixed by two hydraulic clamps.

[0023] Description: By arranging the combined well shaft in the well site, the injection well and the extraction well can be quickly switched, and the two modes do not interfere with each other, which greatly improves the leaching efficiency.

[0024] Further, a plurality of flow guide holes are arranged on the side wall of the main well shaft. An annular space is formed between the main well shaft and the threaded rod. An annular sealing plate is arranged at the top of the annular space. A dosing port is arranged on the annular sealing plate. A wear-resistant gasket is arranged on the outer wall of the sleeve to enhance sliding.

[0025] Further, a plurality of seepage holes are arranged on the extended wellbore sidewall.

[0026] Further, the sleeves are detachably connected through threads, the top of the sleeve is provided with a threaded female screw, the bottom of the sleeve is provided with a threaded male screw, the top of the uppermost sleeve is driven to rotate through a driving motor, the output end of the driving motor is provided with a driving rod, and the driving rod is threadedly connected with the threaded female screw.

[0027] The present application has the following advantages:

[0028] (1) The organic chlorine pesticide contaminated soil in-situ leaching repair process divides the injection well and the extraction well in the organic chlorine pesticide contaminated soil area, and then forms a step-by-step layered leaching mode from inside to outside, and the injection well and the extraction well can be quickly switched, which not only greatly improves the leaching efficiency and facilitates the recovery of the leaching liquid, but also improves the work efficiency, makes the leaching mode more scientific and reasonable, and through the optimization and adjustment of the shape and area of the well position, a complete injection and extraction mode is formed, which can achieve good leaching effect on the organic chlorine pesticide contaminated soil.

[0029] (2) The organic chlorine pesticide contaminated soil in-situ leaching repair process optimizes the types of leaching liquid injected and sprayed, thereby further improving the effect, and Trition X-100 or TWEEN80 is selected for injection leaching, and the non-ionic surfactant or anionic surfactant has its own advantages, the non-ionic surfactant has a lower critical micelle concentration and a stronger solubilization and wrapping capacity for organic pollutants, and can be reasonably selected according to the needs, while hydroxypropyl beta cyclodextrin or carboxymethyl-beta-cyclodextrin has the characteristics of hydrophilic outer edge and hydrophobic inner cavity, and can better adapt to the organic chlorine pesticides in the aqueous phase, and the solubilization mechanism mainly includes that the organic chlorine pesticides are wrapped and embedded in the ring cavity inner shell structure through the cavity inner shell of beta cyclodextrin, and then the organic chlorine pesticides in the soil are captured, so that the removal rate of the organic chlorine pesticides is improved, and the leaching mode of large-area spraying is more suitable, and the two leaching modes are combined as the fourth-stage leaching, thereby realizing deep leaching.

[0030] (3) The organic chlorine pesticide contaminated soil in-situ leaching repair process of the present application can realize the quick switching between the injection well and the extraction well through the combined wellbore in the well position, and the two modes do not interfere with each other, thereby greatly improving the leaching efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a kind of organic chlorine pesticide contaminated soil in-situ leaching repair process flow chart of the present application;

[0032] Figure 2It is the internal structure diagram of the combined well cylinder in the organic chlorine pesticide contaminated soil in-situ leaching repair process of the application;

[0033] Figure 3 It is the casing structure diagram of the combined well cylinder in the organic chlorine pesticide contaminated soil in-situ leaching repair process of the application;

[0034] Figure 4 It is the ring-shaped sealing plate structure diagram of the combined well cylinder in the organic chlorine pesticide contaminated soil in-situ leaching repair process of the application;

[0035] Figure 5 It is the well site layout diagram of step S3-1 primary leaching in the organic chlorine pesticide contaminated soil in-situ leaching repair process of the application;

[0036] Figure 6 It is the well site layout diagram of step S3-2 secondary leaching in the organic chlorine pesticide contaminated soil in-situ leaching repair process of the application;

[0037] Figure 7 It is the well site layout diagram of step S3-3 tertiary leaching in the organic chlorine pesticide contaminated soil in-situ leaching repair process of the application;

[0038] Figure 8 It is the well site layout diagram of step S3-4 quaternary leaching in the organic chlorine pesticide contaminated soil in-situ leaching repair process of the application.

[0039] Wherein, 1-main well cylinder, 11-flow guide hole, 2-filling gravel, 3-stabilizing block, 31-thread hole, 4-extended well cylinder, 41-permeable hole, 5-threaded rod, 6-water pump, 7-casing, 71-driving motor, 72-driving rod, 8-hydraulic clamp, 9-ring-shaped sealing plate, 91-dosing port, 92-wear-resistant gasket. DETAILED DESCRIPTION

[0040] Example 1

[0041] An organic chlorine pesticide contaminated soil in-situ leaching repair process, comprising the following steps:

[0042] As Figure 5 And 6As shown, S1, central well location layout: Ground penetrating radar is used to investigate the boundary and burial depth of the organochlorine pesticide contaminated soil area, determine the area and depth of the organochlorine pesticide contaminated soil area, determine the center point of the organochlorine pesticide contaminated soil area, and set up a central well location at the center point. Three central triangular well locations are set up around the central well location, so that the three central triangular well locations form an equilateral triangle, and the central well location is located at the center of the equilateral triangle. The area of ​​the equilateral triangle formed by the three central triangular well locations is 0.7 times the area of ​​the triangle formed by the three non-adjacent inner ring well locations among the six inner ring well locations.

[0043] like Figure 7 and 8 As shown, S2, the circular well layout: six inner ring wells are arranged around the outside of the central triangular well position to form a ring, and six outer ring wells are arranged around the outside of the inner ring wells to form a ring. The center of the rings formed by the six inner ring wells and the six outer ring wells falls on the central well position. The area of ​​the ring formed by the six inner ring wells is 0.7 times the area of ​​the ring formed by the six outer ring wells.

[0044] S3. Step-by-step rinsing: The rinsing fluid is injected and extracted step by step from the center point well position, the center triangle well position, the six inner ring well positions, and the six outer ring well positions, in pairs from the inside out, to complete the first-stage rinsing, second-stage rinsing, third-stage rinsing, and fourth-stage rinsing.

[0045] The specific steps of the step-by-step rinsing are as follows:

[0046] like Figure 5 As shown, S3-1, first-stage rinsing: The central well location is set as the rinsing fluid injection point, and the three central triangular well locations are set as extraction points. Rinsing fluid injection and extraction are performed respectively, with an injection rate of 0.7 m / s at the injection points. 3 / h, a water pump 6 is installed in the extraction point to keep the water level below the original water level for 4 consecutive days;

[0047] like Figure 6 As shown, S3-2, Secondary rinsing: The injection points in the primary rinsing are shut down, and the three central triangular well positions are set as new injection points, and the six inner ring well positions are set as new extraction points. The rinsing fluid is injected and extracted separately, with an injection rate of 1 m / s². 3 / h, a water pump 6 is installed in the extraction point to keep the water level below the original water level for 8 consecutive days;

[0048] like Figure 7 As shown, S3-3, tertiary rinsing: The injection points in the secondary rinsing are shut down, and three non-adjacent inner ring well positions out of the six inner ring well positions are designated as new injection points. The remaining three inner ring well positions are shut down, and the six outer ring well positions are designated as new extraction points. Rinsing fluid is injected and extracted at each point, with an injection rate of 1.2 m / s.3 / h, water pump 6 is arranged in the extraction point to keep the water level below the original water level, for 6 days, then the three injection points are stopped, the remaining three inner ring well points are set as new extraction points, injection and extraction of the leaching solution are continued, the injection speed of the injection point is 1.2m 3 / h, water pump 6 is arranged in the extraction point to keep the water level below the original water level, for 6 days;

[0049] As shown in Figure 8 S3-4, four-stage leaching: the injection points in the three-stage leaching are stopped, the extraction points continue to work to keep the water level below the original water level, for 2 days, then the center point well point, the center triangle well point and the inner ring well point are all used as injection points, and the leaching solution is sprayed on the surface of the organic chlorine pesticide contaminated soil area inside the circular ring surrounded by the inner ring well point, injection, spraying and extraction of the leaching solution are carried out, the injection speed of the injection point is 0.8-2.3m 3 / h, the injection speed of the center point well point is 2.3m 3 / h, the injection speed of the center triangle well point is 1.2m 3 / h, the injection speed of the inner ring well point is 0.8m 3 / h, the spraying amount is 0.5m 3 / h, water pump 6 is arranged in the extraction point to keep the water level below the original water level, for 6 days;

[0050] The leaching solution injected by the injection point is Trition X-100, and the leaching solution used for spraying on the surface of the organic chlorine pesticide contaminated soil area inside the circular ring surrounded by the inner ring well point in step S3-4 is carboxymethyl-β-cyclodextrin.

[0051] Example 2

[0052] The difference between this embodiment and example 1 is that:

[0053] S1, in the center well point arrangement, the area of the equilateral triangle surrounded by the three center triangle well points is 0.6 times the area of the triangle surrounded by the three non-adjacent inner ring well points among the six inner ring well points;

[0054] S2, in the ring well point arrangement, the area of the circular ring surrounded by the six inner ring well points is 0.6 times the area of the circular ring surrounded by the six outer ring well points.

[0055] Example 3

[0056] The difference between this embodiment and example 1 is that:

[0057] S1, in the center well point arrangement, the area of the equilateral triangle surrounded by the three center triangle well points is 0.8 times the area of the triangle surrounded by the three non-adjacent inner ring well points among the six inner ring well points;

[0058] S2. In the circular well layout, the area of ​​the ring formed by the six inner ring well positions is 0.8 times the area of ​​the ring formed by the six outer ring well positions.

[0059] Example 4

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

[0061] S3-1, First-stage rinsing: The central well location is designated as the rinsing fluid injection point, and the three central triangular well locations are designated as extraction points. Rinsing fluid is injected and extracted separately at each point. The injection rate at the injection point is 0.5 m / s. 3 / h, a water pump 6 is installed in the extraction point to keep the water level below the original water level for 3 consecutive days;

[0062] S3-2, Secondary Flushing: The injection points in the primary flushing are shut off, and the three central triangular well positions are designated as new injection points, and the six inner ring well positions as new extraction points. Flushing fluid is injected and extracted at each point, with an injection rate of 0.5 m / s. 3 / h, a water pump 6 is installed in the extraction point to keep the water level below the original water level for 5 consecutive days;

[0063] S3-3, Third-stage rinsing: The injection points in the second-stage rinsing are shut down. Three non-adjacent inner ring well positions out of the six inner ring well positions are designated as new injection points. The remaining three inner ring well positions are shut down. The six outer ring well positions are designated as new extraction points. Rinsing fluid is injected and extracted at each point. The injection rate at each injection point is 1m. 3 At the extraction point, a water pump 6 is installed to maintain the water level below the original level for 5 consecutive days. Afterward, the three injection points are shut down, and the remaining three inner ring well locations are designated as new extraction points. The injection and extraction of the rinsing fluid continues, with an injection rate of 1 m / s². 3 / h, a water pump 6 is installed in the extraction point to keep the water level below the original water level for 5 consecutive days;

[0064] S3-4, Fourth-stage leaching: The injection points in the third-stage leaching are shut down, while the extraction points continue operating to maintain the water level below the original level for two days. Subsequently, the central well point, central triangular well point, and inner ring well point are all used as injection points. Simultaneously, leaching solution is sprayed onto the surface of the organochlorine pesticide-contaminated soil area within the ring formed by the inner ring well points. This process of injection, spraying, and extraction of the leaching solution is repeated, with an injection rate of 0.5–2 m / s. 3 / h, where the injection rate at the center point well location is 2m. 3 / h, the injection rate at the central triangular well site is 1m 3 / h, the injection rate at the inner ring well site is 0.5m. 3 / h, spraying rate is 0.3m 3 / h, water pump 6 is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 3 days;

[0065] The injected eluent at the injection point is Trition X-100, and the eluent sprayed on the surface of the organic chlorine pesticide contaminated soil region inside the circular ring surrounded by the inner ring well points in step S3-4 is hydroxypropyl β cyclodextrin.

[0066] Example 5

[0067] The difference between this example and example 1 is that:

[0068] S3-1, primary elution: the central point well is set as the eluent injection point, and the three central triangular well points are set as the extraction points, and the injection and extraction of the eluent are carried out respectively, the injection speed of the injection point is 1 m 3 / h, water pump 6 is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 5 days;

[0069] S3-2, secondary elution: the injection point in the primary elution is stopped, and the three central triangular well points are set as new injection points, and the six inner ring well points are set as new extraction points, and the injection and extraction of the eluent are carried out respectively, the injection speed of the injection point is 1.5 m 3 / h, water pump 6 is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 10 days;

[0070] S3-3, tertiary elution: the injection point in the secondary elution is stopped, and the three non-adjacent inner ring well points among the six inner ring well points are set as new injection points, and the remaining three inner ring well points are stopped, and the six outer ring well points are set as new extraction points, and the injection and extraction of the eluent are carried out respectively, the injection speed of the injection point is 1.5 m 3 / h, water pump 6 is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 7 days, then the three injection points are stopped, and the remaining three inner ring well points are set as new extraction points, and the injection and extraction of the eluent are continued, the injection speed of the injection point is 1.5 m 3 / h, water pump 6 is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 7 days;

[0071] S3-4, quaternary elution: the injection point in the tertiary elution is stopped, and the extraction point is continuously worked to keep the water level below the original water level, and the process lasts for 3 days, then the central point well, the central triangular well and the inner ring well are all set as injection points, and the eluent is sprayed on the surface of the organic chlorine pesticide contaminated soil region inside the circular ring surrounded by the inner ring well points, and the injection, spraying and extraction of the eluent are carried out, the injection speed of the injection point is 1-2.5 m 3 / h, wherein the injection speed of the central point well is 2.5 m 3 / h, the injection speed of the central triangular well is 1.5 m3 / h, the injection rate of the inner ring well site is 1 m 3 / h, the spraying amount is 0.7 m 3 / h, the water pump 6 is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 5 days;

[0072] The injected leaching solution at the injection point is TWEEN80, and the leaching solution used for spraying on the surface of the organic chlorine pesticide contaminated soil area in the annular ring surrounded by the inner ring well site in step S3-4 is carboxymethyl-β-cyclodextrin.

[0073] Example 6

[0074] The difference between this embodiment and example 1 is that:

[0075] As shown in Figures 2 to 4 , each well site is arranged with a combined well shaft capable of switching between injection mode and extraction mode, the combined well shaft is provided with a main well shaft 1, the outer wall of the main well shaft 1 is provided with filled gravel 2, the bottom of the main well shaft 1 is provided with a stabilizing block 3, the bottom of the stabilizing block 3 is provided with an extension well shaft 4, a plurality of seepage holes 41 are arranged on the side wall of the extension well shaft 4, a threaded hole 31 is arranged in the middle of the stabilizing block 3, a hollow threaded rod 5 is threadedly connected in the threaded hole 31, a water pump 6 is arranged at the bottom of the threaded rod 5, a plurality of detachable casings 7 are arranged at the top of the threaded rod 5, the uppermost casing 7 extends out of the main well shaft 1, and the casing 7 is externally fixed by two hydraulic clamps 8, a plurality of flow guide holes 11 are arranged on the side wall of the main well shaft 1, an annular space is formed between the main well shaft 1 and the threaded rod 5, an annular sealing plate 9 is arranged at the top of the annular space, a dosing port 91 is formed in the annular sealing plate 9, a wear-resistant gasket 92 is arranged in the middle of the annular sealing plate 9 to enhance the sliding of the outer wall of the casing 7, the casings 7 are threadedly detachably connected, a threaded female nut is arranged at the top of the casing 7, a threaded male nut is arranged at the bottom of the casing 7, the top of the uppermost casing 7 is driven to rotate by a driving motor 71, the driving motor 71 is a commercially available product, a driving rod 72 is arranged at the output end of the driving motor 71, and the driving rod 72 is threadedly connected with the threaded female nut.

[0076] Working principle of the combined well shaft:

[0077] When the leaching solution is injected, the dosing port 91 is opened to inject the leaching solution into the annular space between the main well shaft 1 and the threaded rod 5, and then the leaching solution flows into the filled gravel 2 through the seepage holes 41, and then gradually seeps into the soil. At this time, the leaching solution is prevented from entering the bottom of the combined well shaft under the sealing action of the stabilizing block 3 and the threaded rod 5;

[0078] When switching to extraction mode, close the dosing port 91. First, adjust the height of the water pump 6. The drive motor 71 rotates the drive rod 72, causing the uppermost casing 7 to rotate, which in turn rotates the threaded rod 5 and the water pump 3. During rotation, the threaded rod 5 rotates in connection with the threaded hole 31, thus moving the water pump 3 up and down. If the water pump 3 is located deep enough that a single casing 7 is insufficient to reach the top of the main wellbore 1, additional casing 7 is required. Figure 3 As shown, an additional sleeve 7 is added above the previous sleeve 7 and fixedly connected by threaded male and female threads. Then, the drive rod 72 is connected to the previous sleeve 7. Multiple sleeves 7 can be added in this way. At the same time, when rotating to adjust the height, it is necessary to keep the rotation direction of the drive motor 71 the same as the tightening direction of the threaded male and female threads to prevent the sleeves 7 from falling off each other or the sleeves 7 from falling off the threaded rod 5 during rotation.

[0079] Experimental Example

[0080] The following is a field simulation of the in-situ leaching remediation process for organochlorine pesticide-contaminated soil according to the present invention. A piece of soil severely contaminated by organochlorine pesticides, located at a waste pesticide production plant, was selected. The terrain was flat, and the contaminated groundwater was converted into surface water in the form of springs and flowed into the surrounding rivers. The contaminated area was divided into 4 regions. The degree of contamination in each region was tested and found to be within 10%. Subsequently, experiments were conducted using Examples 1, 3, and 5, as well as conventional spraying leaching methods, as comparative examples. In the conventional spraying method, the leaching agent and dosage were the same as in Example 1, and the treatment time was the total treatment cycle in Example 1. First, the various points were laid out according to the area. The six outer ring well positions, after being laid out, formed a circle that needed to cover at least 90% of the contaminated area. Then, leaching was carried out according to the method in Example 1 and the combined well in Example 4. After leaching, the changes in pollutant concentration inside the contaminated area were statistically analyzed.

[0081] After data analysis, the concentrations and removal rates of each pollutant in Examples 1, 3, 5, and the comparative examples were statistically analyzed, as shown in the table below:

[0082] Table 1 shows the concentrations and removal rates of each pollutant in Examples 1, 3, 5, and the comparative examples.

[0083]

[0084] As can be seen from Table 1, the in-situ leaching process in Examples 1 and 2 can have good leaching effect on the three main pollutants, and the removal rate is high, among which the removal rate in Example 1 is the highest, but the total amount of residual pollutants after leaching in Example 2 is the lowest, which may be due to the fact that the initial pollutants in the block of Example 2 are less, and the distribution mode of Example 2 is more compact in the overall area, so the local leaching effect of pollutants may be better, while the overall removal rate in Example 1 is higher;

[0085] And by comparing Example 3, it can be found that the main difference between Example 3 and Example 1 is the selection of leaching agent, and the change of injection amount is within the reasonable error range given by the process, and has little effect on the result, and finally the removal effect of Example 3 is lower than that of Example 1, which may be because after using the combination of Trition X-100 and carboxymethyl-β-cyclodextrin in the block, the critical micelle concentration of nonionic surfactant is lower, and the solubilization and wrapping capacity for organic pollutants is stronger;

[0086] Finally, we can see that in the comparative example, only a simple surface spraying leaching method is used, and the leaching effect is not ideal, which is not small compared with Examples 1, 3 and 5, which may be related to the soil permeability of the region. The hydraulic conductivity of the soil in this region is 11 cm / s. If the soil permeability of this region is strong, for example, the soil with a hydraulic conductivity greater than 15 cm / s and easy to penetrate, the difference between the comparative example and Examples 1, 3 and 5 may be reduced, which also shows that the in-situ leaching process of the present application can be applied to low permeability contaminated soil with small hydraulic conductivity.

Claims

1. A process for in-situ leach remediation of soil contaminated with organochlorine pesticides, characterized in that, It comprises the following steps: S1, center well site layout: using ground penetrating radar to investigate the area boundary and buried depth of organochlorine pesticide contaminated soil, determine the area and depth of organochlorine pesticide contaminated soil, determine the center point of organochlorine pesticide contaminated soil, and arrange the center point well site at the center point, and arrange three center triangular well sites around the center point well site, so that the three center triangular well sites form an equilateral triangle, and the center point well site is located at the center of the equilateral triangle; S2, ring well site layout: six inner ring well sites are arranged around the outside of the center triangular well site to form a circular ring, and six outer ring well sites are arranged around the outside of the inner ring well site to form a circular ring, the centers of the circular rings formed by the six inner ring well sites and the six outer ring well sites fall on the center point well site; S3, step-by-step leaching: through the center point well site, the center triangular well site, the six inner ring well sites and the six outer ring well sites, the injection and extraction of leaching liquid are carried out step by step, and the first, second, third and fourth leaching are completed. The specific steps of the step-by-step leaching are as follows: S3-1, primary elution: the center point well site is set as the elution injection point, three center triangle well sites are set as extraction points, respectively for elution injection and extraction, the injection speed of the injection point is 0.5~1m 3 / h, the water pump (6) is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 3~5 days; S3-2, secondary leaching: the injection point in the primary leaching is closed, and the three center triangular well sites are set as new injection points, and the six inner ring well sites are set as new extraction points, respectively for injection and extraction of leaching liquid, the injection speed of the injection point is 0.5~1.5m 3 / h, the water pump (6) is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 5~10 days; S3-3, tertiary leaching: the injection point in the secondary leaching is stopped, and three non-adjacent inner ring well sites of the six inner ring well sites are set as new injection points, the remaining three inner ring well sites are stopped, and the six outer ring well sites are set as new extraction points, respectively, to inject and extract the leaching liquid, the injection speed of the injection point is 1~1.5m 3 / h, the water pump (6) is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 5~7 days; subsequently, the three injection points are stopped, the remaining three inner ring well sites are set as new extraction points, and the injection and extraction of the leaching liquid are continued, the injection speed of the injection point is 1~1.5m 3 / h, the water pump (6) is arranged in the extraction point to keep the water level below the original water level, and the process lasts for 5~7 days. S3-4, four-stage leaching: the injection point in the three-stage leaching is stopped, the extraction point is continuously worked to keep the water level below the original water level, and is maintained for 2-3 days, and then the center point well position, the center triangle well position and the inner ring well position are all used as injection points, and the surface of the organochlorine pesticide contaminated soil area inside the circular ring surrounded by the inner ring well position is sprayed with leaching liquid, and the leaching liquid is injected, sprayed and extracted, the injection speed of the injection point is 0.5-2.5 m 3 / h, the spraying amount is 0.3-0.7 m 3 / h, a water pump (6) is arranged in the extraction point to keep the water level below the original water level, and is continuously worked for 3-5 days.

2. The process for in-situ washing remediation of organochlorine pesticide contaminated soil according to claim 1, characterized in that, The area of the equilateral triangle formed by the three center triangular well sites in the step S1 is 0.6-0.8 times the area of the triangle formed by the non-adjacent three inner ring well sites in the six inner ring well sites, and the area of the circular ring formed by the six inner ring well sites in the step S2 is 0.6-0.8 times the area of the circular ring formed by the six outer ring well sites.

3. The process for in-situ washing remediation of organochlorine pesticide contaminated soil according to claim 1, characterized in that, The leaching liquid injected by the injection point in the step S3 is Trition X-100 or TWEEN80, and the leaching liquid used for spraying on the surface of the organochlorine pesticide contaminated soil region inside the circular ring formed by the inner ring well sites in the step S3-4 is hydroxypropyl beta cyclodextrin or carboxymethyl-beta-cyclodextrin.

4. The process for in-situ washing remediation of organochlorine pesticide contaminated soil according to claim 1, characterized in that, The injection rate of the center point well site in the step S3-4 is 2-2.5 m 3 / h, the injection rate of the center triangle well site is 1-1.5 m 3 / h, and the injection rate of the inner ring well site is 0.5-1 m 3 / h.

5. The process for in-situ washing remediation of organochlorine pesticide contaminated soil according to claim 1, wherein, Each well site is provided with a combined well shaft which can switch between injection mode and extraction mode, the combined well shaft is provided with a main well shaft (1), the outer wall of the main well shaft (1) is provided with a filling gravel (2), the bottom of the main well shaft (1) is provided with a stabilizing block (3), the bottom of the stabilizing block (3) is provided with an extension well shaft (4), the middle of the stabilizing block (3) is provided with a threaded hole (31), the threaded hole (31) is internally threadedly connected with a hollow threaded rod (5), the bottom of the threaded rod (5) is provided with a water pump (6), the top of the threaded rod (5) is provided with a plurality of detachably connected sleeves (7), the uppermost one of the sleeves (7) extends out of the main well shaft (1), and the sleeve (7) is externally assisted and fixed by two hydraulic clamps (8).

6. An in-situ washing remediation process of organochlorine pesticide contaminated soil according to claim 5, characterized in that, The side wall of the main well shaft (1) is provided with a plurality of flow guide holes (11), and the annular space is formed between the main well shaft (1) and the threaded rod (5), the top of the annular space is provided with an annular sealing plate (9), the annular sealing plate (9) is provided with a dosing port (91), and the middle of the annular sealing plate (9) is provided with a wear-resistant gasket (92) for enhancing sliding of the outer wall of the sleeve (7).

7. An in-situ washing remediation process of organochlorine pesticide contaminated soil according to claim 5, characterized in that, The side wall of the extension well shaft (4) is provided with a plurality of seepage holes (41).

8. An in-situ washing remediation process of organochlorine pesticide contaminated soil according to claim 5, characterized in that, The various sleeves (7) are detachably linked by threads, the top of the sleeve (7) is provided with a threaded female, the bottom of the sleeve (7) is provided with a threaded male, the top of the uppermost sleeve (7) is driven to rotate by a driving motor (71), the output end of the driving motor (71) is provided with a driving rod (72), and the driving rod (72) is in threaded connection with the threaded female.

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