A low permeability organic contaminated soil solubilization multi-phase extraction remediation system and method

Abstract

This invention discloses a solubilization and multiphase extraction remediation system and method for low-permeability organic-contaminated soil, relating to the field of soil remediation. The remediation system includes a solubilization reagent tank, a metering pump, an injection well, a drainage board, a horizontal well, a self-priming pump, and a tailings collection device. The remediation method involves injecting the solubilization reagent into the upper part of the low-permeability contaminated area using the metering pump. A horizontal well is constructed in the lower part of the contaminated area. A drainage board is installed through the low-permeability contaminated area, with its end hydraulically connected to the horizontal well. The extraction negative pressure generated by the self-priming pump drives the solubilization reagent through the drainage board, leaching the low-permeability soil layer before entering the horizontal well and finally entering the tailings collection device for purification. This invention utilizes the drainage board to improve the permeability of organic-contaminated soil and couples solubilization leaching with multiphase extraction technology, overcoming the bottleneck problem of difficult removal of organic pollutants in low-permeability soil layers. The operation process is simple, significantly shortening the remediation time, and has broad engineering application prospects.

Description

Technical Field

[0001] This invention belongs to the field of soil remediation technology, specifically relating to a solubilization and multiphase extraction remediation system and method for low-permeability organic-contaminated soil, suitable for silty clay and clay with permeability coefficients below 1×10⁻⁶. -5 Contaminated sites with a flow rate of cm / s. Background Technology

[0002] Major organic pollutants include polycyclic aromatic hydrocarbons (PAHs), chlorinated hydrocarbons, petroleum hydrocarbons, and benzene compounds. Organic pollution often remains in the soil as non-aqueous liquids (NAPLs), posing a significant challenge to remediation efforts. Furthermore, over 60% of contaminated sites are composed primarily of low-permeability soils such as silty clay, clay, and muddy clay, making the removal of organic pollutants from these soils particularly difficult. Pollutants diffuse into low-permeability areas and gradually accumulate. When the external pollution concentration falls below the concentration within the low-permeability area, the accumulated organic pollutants will diffuse back into the soil, becoming a persistent secondary source of pollution. Back diffusion in low-permeability organically contaminated soils is one of the greatest technical challenges currently facing the management of groundwater contaminated sites worldwide.

[0003] The evaluation of groundwater remediation effectiveness has clear requirements. Under the premise that the remediation facilities are no longer operational and the groundwater flow field at the site is basically stable, continuous monitoring and evaluation must be carried out for two years. Only if the concentration of target pollutants in the groundwater does not show a significant rebound and does not exceed the corresponding remediation target value within this period can the groundwater remediation be judged to have met the standards. If reverse diffusion exists in the low-permeability soil layer within the site, it will cause the concentration of target pollutants to rebound and even exceed the remediation target value. This will greatly affect the remediation efficiency and seriously hinder the development and utilization of the site.

[0004] Current technologies for the remediation of low-permeability soil layers have the following problems:

[0005] (1) Conventional multiphase extraction technology has low extraction efficiency and poor remediation effect due to poor soil permeability;

[0006] (2) Soil leaching technology has a long remediation cycle and high cost because the agents are difficult to distribute evenly;

[0007] (3) Existing horizontal-vertical well combined extraction methods cannot solve the problem of insufficient flow channels in low-permeability areas.

[0008] The above technical issues urgently need to be resolved. Summary of the Invention

[0009] Objective of the Invention: The objective of this invention is to provide a highly efficient multiphase extraction remediation system for low-permeability organically contaminated soil. Another objective of this invention is to provide a multiphase extraction remediation method for low-permeability organically contaminated soil.

[0010] Technical solution: The present invention proposes a low-permeability organic contaminated soil solubilization multiphase extraction remediation system, characterized in that it includes a solubilization reagent tank, a metering pump, an injection well, a drainage board, a horizontal well, a self-priming pump, and a tail liquid collection device;

[0011] The solubilizing reagent tank is connected to the metering pump, the metering pump is connected to the injection well, and the drainage board is inserted through the low-permeability organic contaminated soil layer and forms a hydraulic connection with the horizontal well.

[0012] The tail liquid collection device is connected to a self-priming pump, which is connected to a horizontal well. The screened section of the horizontal well is located below the organic contaminated soil layer.

[0013] In the above technical solution, the solubilizing reagent in the solubilizing reagent tank is injected into the upper area of ​​the low-permeability organic contaminated soil layer via a metering pump and an injection well; several drainage boards are evenly inserted into the contaminated soil layer to form a flow channel in the low-permeability contaminated area; under the suction negative pressure generated by the self-priming pump, the solubilizing reagent enters the low-permeability organic contaminated soil layer through the drainage boards and leaches the contaminated soil; the leaching tail liquid enters the horizontal well and finally enters the tail liquid collection device for purification treatment.

[0014] Furthermore, the drainage board is a plastic drainage board.

[0015] Furthermore, the drainage board is set parallel to the injection well.

[0016] Furthermore, the drainage board includes a geotextile filter layer and a core board, wherein the geotextile filter layer covers the core board.

[0017] On the other hand, the present invention provides a remediation method utilizing the above-mentioned low-permeability organic contaminated soil solubilization multiphase extraction remediation system, comprising the following steps:

[0018] (1) Add the solubilizing reagent to the solubilizing reagent container;

[0019] (2) Construct injection wells on site and use metering pumps to inject solubilizing agents into the upper area of ​​low-permeability organic contaminated soil layer.

[0020] (3) Construct horizontal wells within the site, with the screening section located below the low-permeability organic contaminated soil layer;

[0021] (4) Several drainage boards are evenly inserted into the contaminated soil layer to form a flow channel in the low-permeability contaminated area and to form hydraulic connection with the horizontal well.

[0022] (5) Connect the self-priming pump pipeline to the horizontal well and start extraction. Under the negative pressure of extraction formed by the self-priming pump, the solubilizing agent enters the low-permeability organic contaminated soil layer through the drainage board and leaches the contaminated soil.

[0023] (6) The extracted fluid from the horizontal well enters the tail fluid collection device for purification.

[0024] Furthermore, in step (1), the solubilizing agent is selected from: sodium dodecyl sulfate, polysorbate 80, and saponin.

[0025] Furthermore, in step (1), the concentration of the solubilizing reagent solution is 0.5-3 wt%.

[0026] Furthermore, in step (2), the permeability coefficient of the low-permeability organically contaminated soil layer is less than 1×10⁻⁶. -5 cm / s.

[0027] Furthermore, in step (4), the water-guiding cross-section of the drainage board is 5-10cm. 2

[0028] Further, in step (5), the self-priming pump pipeline is connected to the horizontal well and extraction begins, with an extraction time of 48 hours or more.

[0029] In existing technologies, hydraulic fracturing is used to create fracture channels and inject solubilizing agents into low-permeability formations. Compared with this technology, the drainage board used in this invention has the following advantages:

[0030] (1) The present invention can effectively promote the uniform diffusion and transport of solubilizing agents through the flow channel formed by the drainage board, and significantly improve the solute transport efficiency in low-permeability contaminated soil layers. In contrast, the fracture network generated by hydraulic fracturing technology usually exhibits significant spatial heterogeneity, and its aperture distribution and dominant distribution direction are uncontrollable, which easily forms local dominant seepage channels, resulting in the loss of solubilizing agents and reduced leaching efficiency.

[0031] (2) The drainage channel formed by the drainage board technology of this invention has controllable geometric dimensions and directional distribution characteristics. The construction process only generates local disturbances, which can effectively avoid the bypass effect and secondary pollution risk commonly seen in subsequent multiphase extraction and repair processes. The cracks generated by hydraulic fracturing technology can damage the structural integrity of low-permeability soil, and the resulting stress redistribution may induce the degradation of the engineering barrier performance.

[0032] (3) Compared with fracturing technology, the present invention connects the solubilizing agent injection module with the horizontal well multiphase extraction-tail fluid collection module through a drainage plate, which significantly improves the rinsing efficiency and the recovery rate of solubilizing agents in the tail fluid, and reduces material costs.

[0033] This invention utilizes drainage boards to improve the permeability of low-permeability organic-contaminated soil layers and provides a flow channel for the injection of solubilizing agents and the extraction of leaching solutions. It realizes the coupled use of two remediation technologies, solubilizing leaching and multiphase extraction, further expanding the application scope of solubilizing leaching and multiphase extraction and improving the remediation efficiency of low-permeability organic-contaminated soil.

[0034] Compared with the prior art, the present invention has the following significant advantages:

[0035] (1) The present invention proposes a solubilization and multiphase extraction remediation system and method for low-permeability organic contaminated soil, which applies plastic drainage board to the remediation of low-permeability organic contaminated soil, breaks through the technical bottleneck that soil washing and multiphase extraction technology cannot remediate low-permeability soil, and solves the problem of reverse diffusion of organic pollution in low-permeability soil.

[0036] (2) The low-permeability organic contaminated soil solubilization multiphase extraction remediation system and method proposed in this invention combines soil washing and multiphase extraction, which significantly shortens the remediation time.

[0037] (3) The low-permeability organic contaminated soil solubilization multiphase extraction remediation system and method proposed in this invention involves mature construction technology, short construction period and low cost.

[0038] (4) The low-permeability organic contaminated soil solubilization multiphase extraction remediation system and method proposed in this invention belongs to in-situ remediation technology, which has less disturbance to the site and is applicable to a wide range of site conditions.

[0039] (5) The low-permeability organic contaminated soil solubilization multiphase extraction remediation system and method proposed in this invention can simultaneously remove gaseous and liquid contaminants from the soil, and is applicable to a wide range of contaminants.

[0040] (6) The low-permeability organic contaminated soil solubilization multiphase extraction remediation system and method proposed in this invention contains surfactants in the recovered tail liquid, which can be reused after separation and treatment, in line with the requirements of circular economy. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the low-permeability organic contaminated soil solubilization multiphase extraction remediation system of the present invention. In the figure: 1 is the solubilization reagent tank; 2 is the metering pump; 3 is the injection well; 4 is the drainage board; 5 is the horizontal well; 6 is the self-priming pump; and 7 is the tail liquid collection device.

[0042] Figure 2 This is a flowchart of the low-permeability organic contaminated soil solubilization and multiphase extraction remediation method in this invention.

[0043] Figure 3 This is a cross-sectional view of the drainage board in this invention. In the figure: 41 is the geotextile filter layer; 42 is the core board. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0045] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0046] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0047] Example 1

[0048] like Figure 1 As shown in the figure, this embodiment provides a low-permeability organic contaminated soil solubilization and multiphase extraction remediation system, including a solubilization reagent tank 1, a metering pump 2, an injection well 3, a drainage board 4, a horizontal well 5, a self-priming pump 6, and a tailings collection device 7. The solubilization reagent tank 1 is connected to the metering pump 2 and is used to inject the solubilization reagent solution into the soil layer. The injection well 3 is connected to the metering pump 2 and is located in the upper region of the low-permeability organic contaminated soil layer. The tailings collection device 7 is connected to the self-priming pump 6, which is connected to the horizontal well 5. The horizontal well 5 includes an open-screen section; the open-screen section of the horizontal well 5 is located in the lower part of the low-permeability organic contaminated soil layer. The drainage board 4 is inserted into the low-permeability contaminated soil layer and approaches the horizontal well. The self-priming pump 6 is connected to the tailings collection device 7 and is used to extract and collect wastewater from the horizontal well 5.

[0049] In this embodiment, a closed-loop passage is formed by using a drainage board. The solubilizing agent enters the low-permeability organic contaminated soil layer through the solubilizing agent tank 1, metering pump 2, injection well 3, and drainage board 4. After the solubilizing agent leaches the organic contaminated soil layer, the leaching tail liquid is recovered through the drainage board 4, horizontal well 5, self-priming pump 6, and tail liquid collection device 7.

[0050] The solubilizing agent is mainly a surfactant solution. Since the low-permeability soil layer contains a large amount of clay particles, the adsorption loss of surfactant should be avoided as much as possible during use. Anionic or nonionic surfactants should be preferred as solubilizing agents.

[0051] The drainage board 4 includes a geotextile filter layer 41 and a core board 42, wherein the geotextile filter layer 41 covers the core board 42. The core board 42 is composed of several cross-shaped structures connected in parallel, wherein the pores between each cross-shaped structure and the geotextile filter layer serve as water-conducting channels. In this embodiment, the drainage board is a plastic drainage board. The cross-sectional area of ​​the water-conducting channel of the plastic drainage board should be selected according to the soil characteristics of the low-permeability zone, and the cross-sectional dimensions need to be determined in advance through small-scale tests. In this embodiment, the water-conducting cross-section of the plastic drainage board is optimized to 5cm through small-scale tests. 2 .

[0052] The plastic drainage board passing through the low-permeability organic contaminated soil layer must be close to the horizontal well section 5 to form hydraulic connection, ensuring the smooth progress of solubilization leaching and multiphase extraction remediation.

[0053] Example 2

[0054] This embodiment applies the remediation system from Embodiment 1 to the remediation of low-permeability organic contaminated sites, such as... Figure 2 As shown, the specific steps include:

[0055] Step (1): Prepare a solubilizing agent suitable for organic pollutants in low-permeability soil layers and store it in solubilizing agent container 1;

[0056] Step (2): Construct injection well 3 on site and use metering pump 2 to inject solubilizing agent into the upper area of ​​low-permeability organic contaminated soil layer;

[0057] Step (3): Construct horizontal well 5 on site, with the screen section located below the low-permeability organic contaminated soil layer;

[0058] Step (4): Insert the plastic drainage board 4 into the low-permeability organic contaminated soil layer and make hydraulic connection with the horizontal well 5.

[0059] Step (5): Connect the self-priming pump 6 pipeline to the horizontal well 5 and start extraction. The solubilizing agent can enter the horizontal well 5 through the plastic drainage board 4, and at the same time, the low-permeability organic contaminated soil layer is rinsed.

[0060] In step (6), the extracted fluid in the horizontal well enters the tail fluid collection device 7 for tail fluid treatment.

[0061] Example 3

[0062] This embodiment is based on Embodiment 1 and Embodiment 2, and a small-scale remediation test of low-permeability organic contaminated soil was carried out. The specific steps are as follows:

[0063] Step 1: The experiment was conducted in a stainless steel cylindrical soil model, 12cm high and 8cm in diameter, with a 4cm thick sand cushion layer at the bottom. A plastic drainage board (11.5cm long and 6.5cm wide) was inserted in the middle. In this embodiment, the solubilizing agent used was polysorbate 80 solution with a concentration of 1.4wt%, and the test soil sample had a permeability coefficient of 2×10⁻⁶. -6 Diesel fuel contaminated clay at a speed of cm / s. The contaminated clay was filled into the model, surrounding a plastic drainage board, to a total thickness of 8 cm. The top and bottom of the model were sealed with flanges, with inlet and outlet ports located at the center of the flanges.

[0064] Step 2: Polysorbate 80 solution is injected from the top flange inlet using a peristaltic pump. After passing through the soil column, it flows out from the bottom flange outlet. The eluent is collected for testing and analysis.

[0065] Step 3: After rinsing for 30 PV, stop the injection and connect the top flange injection port to the multiphase extraction device (including gas-liquid separator, vacuum pump, rotor flow meter and activated carbon column). Start the vacuum pump and extract for 48 hours until the quality of the extraction tail liquid is stable, then stop the extraction.

[0066] Step 4: Samples were taken from the remediated low-permeability organic contaminated soil and the extracted tailings for testing. The test results showed that the diesel removal rate in the contaminated soil reached 32.5%, and the recovery rate of polysorbate 80 in the tailings was >80%.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 3 is that a plastic drainage board is not used in step 1. The remaining steps are the same. Samples of the remediated low-permeability organic-contaminated soil and the extraction tailings were taken for testing. The test results showed that for low-permeability contaminated soil, without the use of a plastic drainage board, the injection and extraction of the solubilizing agent could not be achieved, and the pollutant removal rate was less than 5%. However, using the remediation method of this invention, the diesel removal rate in low-permeability contaminated soil increased to 32.5%, significantly better than conventional solubilization-enhanced extraction technology. This remediation method effectively removes organic pollutants from low-permeability soil, overcoming the technical bottleneck that conventional soil washing and multiphase extraction cannot be used for low-permeability soil layers.

[0069] Comparative Example 2

[0070] This comparative study used hydraulic fracturing injection for the remediation of low-permeability organically contaminated soil, with engineering parameters based on the numerical model established in the literature "Study on the Remediation Efficiency of Hydraulic Regulation of Typical NAPL Contaminated Sites in Shanghai". The results showed that under fracturing and permeability enhancement conditions, the pollutant removal rate reached 54.0% after 1080 days of continuous extraction. In contrast, the method proposed in this invention, under laboratory-scale conditions (Example 3), achieved a pollutant removal rate of over 60% after only 6 days of solubilization and extraction remediation, significantly shortening the remediation time.

Claims

1. A remediation method utilizing a low-permeability organic contaminated soil solubilization multiphase extraction remediation system, characterized in that, The system includes a solubilizing reagent tank, a metering pump, an injection well, a drainage board, a horizontal well, a self-priming pump, and a tail liquid collection device. The solubilizing reagent tank is connected to the metering pump, which is connected to the injection well. The drainage board is inserted through a low-permeability organic contaminated soil layer and forms a hydraulic connection with the horizontal well. The tail liquid collection device is connected to the self-priming pump, which is connected to the horizontal well. The open-screen section of the horizontal well is located below the organic contaminated soil layer. The drainage board is arranged parallel to the injection well. The drainage board includes a geotextile filter layer and a core plate, with the geotextile filter layer covering the core plate. The core plate is composed of several parallel cross structures, with the pores between each cross structure and the geotextile filter layer serving as water-conducting channels. The repair method includes the following steps. (1) Add solubilizing reagent to the solubilizing reagent container; (2) Construct injection wells on site and use metering pumps to inject solubilizing agents into the upper area of ​​low-permeability organic contaminated soil layer; (3) Construct horizontal wells within the site, with the screening section located below the low-permeability organic contaminated soil layer; (4) Several drainage boards are evenly inserted into the contaminated soil layer to form a flow channel in the low-permeability contaminated area and to form hydraulic connection with the horizontal well. (5) Connect the self-priming pump pipeline to the horizontal well and start extraction. Under the negative pressure of extraction formed by the self-priming pump, the solubilizing agent enters the low-permeability organic contaminated soil layer through the drainage board and leaches the contaminated soil. (6) The extracted fluid from the horizontal well enters the tail fluid collection device for purification treatment.

2. The repair method according to claim 1, characterized in that, In step (1), the solubilizing agent is selected from: sodium dodecyl sulfate, polysorbate 80, and saponin.

3. The repair method according to claim 1, characterized in that, In step (1), the concentration of the solubilizing reagent solution is 0.5-3 wt%.

4. The repair method according to claim 1, characterized in that, In step (2), the permeability coefficient of the low-permeability organically contaminated soil layer is less than 1×10⁻ 5 cm / s.

5. The repair method according to claim 1, characterized in that, In step (4), the water-conducting cross-section of the drainage board is 5-10 cm².

6. The repair method according to claim 1, characterized in that, In step (5), the self-priming pump pipeline is connected to the horizontal well and extraction begins, with an extraction time of 48 hours or more.

7. The repair method according to claim 1, characterized in that, In step (4), the drainage board is a plastic drainage board.

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