Solubilization multiphase extraction remediation system and method for low-permeability organic polluted soil

Abstract

The invention discloses a solubilizing multiphase extraction remediation system and method for low-permeability organic contaminated soil, and relates to the field of soil remediation. The repairing system comprises a solubilizing reagent tank, a metering pump, an injection well, a drainage plate, a horizontal well, a self-priming pump and a tail liquid collecting device. The remediation method comprises the steps that a solubilizing reagent is injected into the upper portion of the low-permeability polluted area through a metering pump, a horizontal well is constructed on the lower portion of the polluted area, a drainage plate is arranged to penetrate through the low-permeability polluted area, the tail end of the drainage plate is in hydraulic communication with the horizontal well, and extraction negative pressure formed by a self-priming pump drives the solubilizing reagent to pass through the drainage plate; and after the low-permeability soil layer is leached, entering the horizontal well, and finally entering the tail liquid collecting device for purification. According to the method, the permeability of the organic polluted soil is improved by utilizing the drainage plate, solubilizing leaching and multiphase extraction technologies are coupled and combined, the bottleneck problem that organic pollutants in a low-permeability soil layer are difficult to remove is solved, the operation process is simple and convenient, the repairing time is remarkably shortened, and the method has a wide engineering application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil remediation, and specifically relates to a low-permeability organic contaminated soil solubilization multiphase extraction remediation system and method, which is suitable for silty clay, clay and other soils with a permeability coefficient lower than 1×10 -5 cm / s of contaminated sites. Background Art

[0002] The main organic pollutants include polycyclic aromatic hydrocarbons, chlorinated hydrocarbons, petroleum hydrocarbons and benzene series. Organic pollution often remains in the soil in the form of non-aqueous phase liquid (NAPL), which brings huge challenges to remediation work. In addition, contaminated sites mainly composed of low-permeability soils such as silty clay, clay and silty clay account for more than 60%, and the removal of organic pollutants in this type of soil is particularly difficult. Pollutants enter low-permeability areas by diffusion and gradually accumulate. When the external pollution concentration is lower than the pollution concentration in the low-permeability area, the accumulated organic pollutants will diffuse in the opposite direction and become a persistent secondary pollution source. Backward diffusion in low-permeability organic contaminated soil is one of the biggest technical challenges currently facing the management of groundwater contaminated sites around the world.

[0003] There are clear requirements for the evaluation of groundwater remediation effects. On the premise that the remediation facilities have stopped operating and the groundwater flow field on the site is basically stable, continuous monitoring and evaluation shall be carried out for 2 years. Only if the concentration of target pollutants in the groundwater does not show a significant rebound increase and does not exceed the corresponding remediation target value during this period, can the groundwater remediation of the site be judged to have met the standards. If there is reverse diffusion in the low-permeability soil layer on the site, the concentration of target pollutants will rebound and even exceed the remediation target value, which will greatly affect the remediation efficiency and seriously hinder the development and utilization of the site.

[0004] The current repair technology for low permeability soil has 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 is difficult to evenly distribute the agent, resulting in a long remediation cycle and high cost;

[0007] (3) The existing horizontal well-vertical well combined extraction method cannot solve the problem of insufficient diversion channels in low permeability areas.

[0008] The above technical problems need to be solved. Summary of the invention

[0009] Purpose of the invention: The purpose of the present invention is to provide a low permeability organic contaminated soil solubilization multiphase extraction remediation system with high remediation efficiency. Another purpose of the present invention is to provide a low permeability organic contaminated soil solubilization multiphase extraction remediation method.

[0010] Technical solution: The present invention proposes a low-permeability organic contaminated soil solubilization multiphase extraction remediation system, which is characterized by comprising 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 agent 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, the self-priming pump is connected to a horizontal well, and a screening section of the horizontal well is located below the organic contaminated soil layer.

[0013] In the above technical scheme, the solubilizing reagent in the solubilizing reagent tank is injected into the upper area of ​​the low permeability organic contaminated soil layer through a metering pump and an injection well; a number of drainage boards are evenly inserted in the contaminated soil layer to form a diversion channel in the low permeability contaminated area; under the action of the extraction negative pressure formed by the self-priming pump, the solubilizing reagent enters the low permeability organic contaminated soil layer through the drainage board and leaches the contaminated soil; the tail liquid after elution enters the horizontal well and finally enters the tail liquid collection device for purification treatment.

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

[0015] Furthermore, the drainage plate is arranged in parallel with the injection well.

[0016] Furthermore, the drainage board includes a geotextile filter layer and a core board, wherein the geotextile filter layer is coated on the outside of the core board.

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

[0018] (1) Adding a solubilizing reagent into a solubilizing reagent tank;

[0019] (2) Construct an injection well on site and use a metering pump to inject the solubilizing agent into the upper area of ​​the low-permeability organic contaminated soil layer;

[0020] (3) A horizontal well is constructed on site, with the screening section located below the low-permeability organic contaminated soil layer;

[0021] (4) inserting a plurality of drainage boards evenly in the contaminated soil layer to form a diversion channel in the low permeability contaminated area and close to the horizontal well to form a hydraulic connection;

[0022] (5) connecting the self-priming pump pipeline to the horizontal well and starting extraction. Under the action of the extraction negative pressure 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 in the horizontal well enters the tail liquid 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 agent solution is 0.5-3 wt %.

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

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

[0028] Furthermore, in step (5), a self-priming pump pipeline is connected to the horizontal well and extraction is started, and the extraction time is greater than or equal to 48 hours.

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

[0030] (1) The diversion channel formed by the drainage board of the present invention can effectively promote the uniform diffusion and migration of the solubilizing agent, and significantly improve the solute migration efficiency in the low-permeability contaminated soil layer. In contrast, the fracture network produced by the fracturing technology usually shows significant spatial heterogeneity, and its aperture distribution and dominant distribution direction are uncontrollable, which is easy to form a local dominant seepage channel, resulting in the loss of the solubilizing agent and reducing the elution efficiency.

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

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

[0033] The present invention utilizes drainage boards to improve the permeability of low-permeability organically contaminated soil layers, and provides a diversion channel for the injection of solubilizing agents and the extraction of leaching solutions, thereby realizing the coupled use of the two remediation technologies of solubilization leaching and multiphase extraction, further expanding the application scope of solubilization leaching and multiphase extraction, and improving the remediation efficiency of low-permeability organically contaminated soils.

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

[0035] (1) The present invention proposes a low-permeability organic contaminated soil solubilization multiphase extraction remediation system and method, which applies plastic drainage boards to the remediation of low-permeability organic contaminated soil, breaking through the technical bottleneck that soil leaching and multiphase extraction technologies cannot repair low-permeability soils, and solving the problem of reverse diffusion of organic pollution in low-permeability soils.

[0036] (2) The low-permeability organic contaminated soil solubilization multiphase extraction remediation system and method proposed in the present invention couples soil leaching and multiphase extraction to significantly shorten the remediation time.

[0037] (3) The low-permeability organic contaminated soil solubilization multiphase extraction remediation system and method proposed in the present invention have 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 the present invention belongs to the in-situ remediation technology, which has little 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 the present invention can simultaneously remove gas and liquid pollutants in the soil, and is applicable to a wide range of pollutant types.

[0040] (6) The low-permeability organic contaminated soil solubilization multiphase extraction remediation system and method proposed in the present invention contains surfactants in the recovered tail liquid, which can be reused after separation treatment, meeting the requirements of circular economy. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0042] Figure 2 The present invention is a flow chart of the solubilization multiphase extraction remediation method for low permeability organic contaminated soil.

[0043] Figure 3 It is a structural cross-sectional view of the drainage board in the present invention. In the figure: 41 is a geotextile filter layer; 42 is a core board. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

[0046] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0047] Example 1

[0048] like Figure 1 As shown, a low permeability organic contaminated soil solubilization multiphase extraction remediation system provided in this embodiment includes 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 tail liquid 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 area of ​​the low permeability organic contaminated soil layer. The tail liquid collection device 7 is connected to the self-priming pump 6, and the self-priming pump 6 is connected to the horizontal well 5. The horizontal well 5 includes a screening section; the screening section of the horizontal well 5 is located at the lower part of the low permeability organic contaminated soil layer, and the drainage board 4 is inserted into the low permeability contaminated soil layer and close to the horizontal well. The self-priming pump 6 is connected to the tail liquid collection device 7, and is used to extract and collect the sewage in the horizontal well 5.

[0049] In this embodiment, a closed-loop passage is formed by using a drainage board, and the solubilizing reagent enters the low-permeability organic contaminated soil layer through the solubilizing reagent tank 1, the metering pump 2, the injection well 3, and the drainage board 4. After the solubilizing reagent leaches the organic contaminated soil layer, the eluted tail liquid is recovered through the drainage board 4, the horizontal well 5, the self-priming pump 6 and the 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 the surfactant should be avoided as much as possible during use, and anionic or non-ionic surfactants are preferably selected as solubilizing agents.

[0051] The drainage board 4 includes a geotextile filter layer 41 and a core plate 42, wherein the geotextile filter layer 41 is coated on the outside of the core plate 42. The core plate 42 is composed of a number of cross structures in parallel, wherein the pores between each cross structure and the geotextile filter layer are water channels. The drainage board of this embodiment is a plastic drainage board, and the cross section of the water channel of the plastic drainage board should be selected according to the soil characteristics of the low permeability area, and the cross-sectional size needs to be determined in advance through a small test. In this embodiment, the water channel cross section of the plastic drainage board is optimized to 5cm after a small test. 2 .

[0052] The plastic drainage board passing through the low-permeability organic contaminated soil layer must be close to the 5 opening screen sections of the horizontal well to form hydraulic connectivity and ensure the smooth progress of solubilization leaching and multiphase extraction and repair.

[0053] Example 2

[0054] In this embodiment, the repair system in Example 1 is applied to repair low-permeability organic contaminated sites, such as Figure 2 As shown, the specific steps include:

[0055] Step (1), preparing a solubilizing agent suitable for organic pollutants in low permeability soil layers, and storing the solubilizing agent in a solubilizing agent tank 1;

[0056] Step (2), constructing an injection well 3 in the site, and injecting the solubilizing agent into the upper area of ​​the low-permeability organic contaminated soil layer using a metering pump 2;

[0057] Step (3), constructing a horizontal well 5 in the site, with the screening section located below the low-permeability organic contaminated soil layer;

[0058] Step (4), inserting the plastic drainage board 4 into the low-permeability organic contaminated soil layer and approaching the horizontal well 5 to form hydraulic communication;

[0059] Step (5), connecting the pipeline of the self-priming pump 6 to the horizontal well 5 and starting 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 eluted;

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

[0061] Example 3

[0062] This example carries out a small test for the restoration of low-permeability organic contaminated soil based on Example 1 and Example 2, which specifically includes the following steps:

[0063] Step 1, the test was carried out in a stainless steel cylindrical soil column model, the model was 12 cm high, 8 cm in diameter, a 4 cm thick sand cushion was laid on the bottom, and a plastic drain board (11.5 cm long, 6.5 cm wide) was inserted in the middle. In this embodiment, the solubilizing agent was polysorbate 80 solution with a concentration of 1.4 wt%, and the test soil sample had a permeability coefficient of 2×10 -6 cm / s diesel contaminated clay. The contaminated soil was filled into the model around the plastic drain board, with a total thickness of 8cm. The top and bottom of the model were sealed with flanges, and the inlet and outlet were set at the center of the flange.

[0064] Step 2: Inject the polysorbate 80 solution from the top flange water inlet through a peristaltic pump, and let it flow out from the bottom flange water outlet after passing through the soil column. Collect the eluate for testing and analysis.

[0065] Step 3, after eluting for 30 PV, stop injection, connect the top flange injection port to the multiphase extraction device (including gas-liquid separation tank, vacuum pump, rotor flowmeter and activated carbon column), start the vacuum pump, extract for 48 hours until the quality of the extracted tail liquid is stable, and then stop extraction.

[0066] Step 4, the repaired low-permeability organic contaminated soil and the extracted tail liquid were sampled and tested. 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 tail liquid was >80%.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 3 is that plastic drain boards are not used in step 1. The remaining steps are the same. The repaired low-permeability organic contaminated soil and the extraction tail liquid are sampled and tested. The test results show that for low-permeability contaminated soil, the injection and extraction of solubilizing agents cannot be achieved without the use of plastic drain boards, and the pollutant removal rate is less than 5%. However, by applying the repair method of the present invention, the diesel removal rate in low-permeability contaminated soil is increased to 32.5%, which is significantly better than conventional solubilization and enhanced extraction technology. This repair method achieves the effective removal of organic pollutants in low-permeability soil, breaking through the technical bottleneck that conventional soil leaching and multiphase extraction cannot be used for low-permeability soil layers.

[0069] Comparative Example 2

[0070] This comparative example uses the fracturing injection method to repair low-permeability organic contaminated soil, and its engineering parameter system refers to the numerical model established in the document "Study on the Efficiency of Hydraulic Regulation and Remediation of Typical NAPL Contaminated Sites in Shanghai". The research results show that under the conditions of fracturing and permeability enhancement, the pollutant removal rate after 1080 days of continuous extraction reaches 54.0%. However, under the conditions of laboratory pilot tests (Example 3), the pollutant removal rate of the method proposed in the present invention can reach more than 60% after 6 days of solubilization extraction and repair, which significantly shortens the repair time.

Claims

1. A low permeability organic contaminated soil solubilization multiphase extraction remediation system, characterized in that: It includes a solubilizing agent tank, a metering pump, an injection well, a drainage plate, a horizontal well, a self-priming pump and a tail liquid collection device; The solubilizing agent 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; The tail liquid collection device is connected to a self-priming pump, the self-priming pump is connected to a horizontal well, and a screening section of the horizontal well is located below the organic contaminated soil layer.

2. The low permeability organic contaminated soil solubilization multiphase extraction remediation system according to claim 1 is characterized in that: The drain board is a plastic drain board.

3. The low permeability organic contaminated soil solubilization multiphase extraction remediation system according to claim 1 is characterized in that: The drainage board is arranged parallel to the injection well.

4. The low permeability organic contaminated soil solubilization multiphase extraction remediation system according to claim 1 is characterized in that: The drainage board comprises a geotextile filter layer and a core board, wherein the geotextile filter layer is coated on the outside of the core board.

5. A remediation method using the low permeability organic contaminated soil solubilization multiphase extraction remediation system according to claim 1, characterized in that: The following steps are included: (1) Adding a solubilizing reagent into a solubilizing reagent tank; (2) Construct an injection well on site and use a metering pump to inject the solubilizing agent into the upper area of ​​the low-permeability organic contaminated soil layer; (3) A horizontal well is constructed on site, with the screening section located below the low-permeability organic contaminated soil layer; (4) inserting a plurality of drainage boards evenly in the contaminated soil layer to form a diversion channel in the low permeability contaminated area and close to the horizontal well to form a hydraulic connection; (5) connecting the self-priming pump pipeline to the horizontal well and starting extraction. Under the action of the extraction negative pressure 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 in the horizontal well enters the tail liquid collection device for purification.

6. The repair method according to claim 5, characterized in that: In step (1), the solubilizing agent is selected from: sodium dodecyl sulfate, polysorbate 80, and saponin.

7. The repair method according to claim 5, characterized in that: In step (1), the concentration of the solubilizing agent solution is 0.5-3 wt %.

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

9. The repair method according to claim 5, characterized in that: In step (4), the water-conducting section of the drainage board is 5-10 cm 2 .

10. The repair method according to claim 5, characterized in that: In step (5), a self-priming pump pipeline is connected to the horizontal well and extraction is started, and the extraction time is greater than or equal to 48 hours.

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