In-situ leaching repair system and repair process

Abstract

The invention discloses an in-situ leaching remediation system and remediation process. The in-situ leaching remediation system comprises a waterproof curtain arranged on the periphery of soil to be remediated, injection and extraction units arranged at the four corners of a soil area to be remediated and a plurality of point positions in a central area, and water treatment equipment. Each injection and extraction unit comprises an injection well, an extraction well and a chemical injection well which are used for injecting a soil stabilizer, and the injection well and the extraction well are located on the periphery of the chemical injection well. During remediation, a soil stabilizer is injected into the chemical injection well firstly, and then underground water is extracted; a leaching agent is injected through the injection well, leacheate is pumped out through the extraction well after a period of time, and the leacheate is pumped to water treatment equipment; and dismantling the equipment to finish repairing. The soil stabilizer is injected into the bottom of the contaminated soil layer to be matched with the waterproof curtain, longitudinal migration of the leaching agent is slowed down, the leaching agent is prevented from diffusing to surrounding soil, full contact between the leaching agent and pollutants is guaranteed, and the in-situ leaching remediation effect is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of in-situ remediation of contaminated soil, and particularly relates to an in-situ leaching remediation system and a remediation process. Background Art

[0002] Soil heavy metal pollution has become one of the important problems endangering human health and restricting the sustainable development of society. At present, the main methods for remediating heavy metal contaminated soil include soil leaching method, chemical reduction method, solidification / stabilization method, etc. The soil leaching method has become one of the hot research directions in the field of heavy metal contaminated soil remediation due to its advantages such as short remediation cycle, wide treatment range, and low treatment cost. According to the location of the treated soil, the soil leaching method can be divided into in-situ leaching and ex-situ leaching.

[0003] In-situ leaching is a soil remediation technology that directly injects water or leaching agents through seepage ponds and injection wells at the polluted site, allowing the leaching solution to seep through the polluted soil area to promote the dissolution and migration of heavy metal pollutants in the soil. Existing in-situ leaching methods have certain drawbacks. The radiation range of the leaching agent is limited, and it cannot ensure sufficient contact with the pollutants. At the same time, the groundwater flow field is also one of the influencing factors of in-situ leaching. For polluted areas with complex groundwater flow fields, it is difficult to achieve good remediation effects with in-situ leaching. Summary of the Invention

[0004] The present invention aims at the above problems and provides an in-situ leaching remediation system and a remediation process, which not only overcome the problem of insufficient leaching but also avoid the influence of the groundwater flow field on the in-situ leaching remediation effect.

[0005] The technical solution of the present invention is outlined as follows: Based on the technical principle of injecting soil solidifying agent into the bottom of the polluted soil layer and cooperating with the cut-off curtain built around the soil area to be remediated to slow down the longitudinal migration of the leaching agent, several injection-extraction units composed of injection wells, extraction wells, and medicine injection wells are set in the soil area to be remediated, and the in-situ leaching remediation effect is improved through multi-point injection-extraction operations.

[0006] In order to achieve the above object, the technical solutions adopted by the present invention are as follows:

[0007] In the first aspect of the present invention, an in-situ leaching remediation system is provided, including: a cut-off curtain arranged around the soil to be remediated, injection-extraction units arranged at several points at the four corners and the central area of the soil area to be remediated, and a water treatment device arranged outside the soil area to be remediated and connected to the injection-extraction units.

[0008] Among them, each injection-extraction unit includes an injection well for injecting soil solidifying agent, an extraction well, and a medicine injection well, and the injection well and the extraction well are located outside the medicine injection well.

[0009] Preferably, the distance between adjacent two groups of injection and extraction units does not exceed 20 m; the injection wells and the extraction wells are arranged side by side, and the injection wells are located outside the extraction wells to ensure that the treatment range of the soil curing agent is large enough. A submersible pump is provided in the extraction well, and the water outlet of the submersible pump is connected to the sewage treatment equipment.

[0010] Preferably, the depth of the injection well is 0 - 0.5 m above the top of the contaminated soil layer, the depth of the extraction well is 0 - 0.5 m below the bottom of the contaminated soil layer, and the depth of the chemical injection well is not less than 0.5 m below the bottom of the contaminated soil layer.

[0011] Preferably, the lower ends of the injection wells and the chemical injection wells are closed, and a number of water outlet holes are provided on the well walls.

[0012] Preferably, the cut-off curtain is constructed along the boundary of the soil area to be repaired, and the depth is not less than 1 m below the bottom of the contaminated soil layer.

[0013] In the second aspect of the present invention, an in-situ leaching and remediation process is provided: by injecting a soil curing agent into the bottom of the contaminated soil layer and cooperating with the cut-off curtain constructed around the soil area to be repaired, the longitudinal migration of the leaching agent is slowed down. The specific treatment steps are as follows:

[0014] (1) Construct a cut-off curtain around the soil area to be repaired;

[0015] (2) Arrange a number of injection wells, extraction wells and chemical injection wells in the soil area to be repaired;

[0016] (3) Inject the soil curing agent into the chemical injection wells;

[0017] (4) Extract groundwater through the extraction wells;

[0018] (5) Leaching: Inject the leaching agent into the injection wells, and after a period of time, extract the leaching solution through the extraction wells and pump it to the water treatment equipment;

[0019] (6) Demolish the injection wells, extraction wells and chemical injection wells to complete the remediation.

[0020] Preferably, the cut-off curtain is constructed along the boundary of the soil area to be repaired, and the depth is not less than 1 m below the bottom of the contaminated soil layer; the depth of the injection well is 0 - 0.5 m above the top of the contaminated soil layer, the depth of the extraction well is 0 - 0.5 m below the bottom of the contaminated soil layer, and the depth of the chemical injection well is not less than 0.5 m below the bottom of the contaminated soil layer. The injection wells and the extraction wells are located outside the chemical injection wells, the injection wells and the extraction wells are arranged side by side, and the injection wells are located outside the extraction wells; a submersible pump is provided in the extraction well, and the water outlet of the submersible pump is connected to the sewage treatment equipment.

[0021] Preferably, the form of the soil curing agent is liquid.

[0022] Preferably, in the flushing step, after injecting the flushing agent into the injection well, extraction is carried out 2 to 5 days later, and the entire remediation process is repeated 1 to 2 times.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] By injecting the soil solidifying agent at the bottom of the contaminated soil layer and cooperating with the water-stop curtain built around the area of the soil to be remediated, the longitudinal migration of the flushing agent is effectively slowed down, the diffusion of the flushing agent to the surrounding soil is avoided, the sufficient contact between the flushing agent and the pollutants is ensured, and the in-situ flushing remediation effect is improved. At the same time, the water-stop curtain plays a role in blocking the surrounding groundwater and reduces the influence of the groundwater flow field on the in-situ flushing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a layout schematic diagram of the in-situ flushing remediation system provided by an embodiment of the present invention;

[0026] Figure 2 is Figure 1 the cross-sectional structure schematic diagram of the a-a section in

[0027] Figure 3 It is a process schematic diagram of the in-situ flushing remediation process provided by an embodiment of the present invention.

[0028] The reference numerals and components involved in the drawings are as follows:

[0029] 1 - water-stop curtain; 2 - injection well; 3 - extraction well; 4 - medicine injection well; 5 - water treatment equipment; 6 - submersible pump. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] According to Figure 1 and Figure 2 , the in-situ flushing remediation system 100 provided in this embodiment includes a water-stop curtain 1 arranged around the soil to be remediated, an injection and extraction unit arranged at several points at the four corners and the central area of the soil area to be remediated, and a water treatment equipment 5 arranged outside the soil area to be remediated and connected to the injection and extraction unit.

[0032] The cut-off curtain 1 is constructed along the boundary of the soil area to be repaired, with a depth of not less than 1 m below the bottom of the contaminated soil layer. The spacing between adjacent two sets of injection and extraction units does not exceed 20 m. Each injection and extraction unit includes an injection well 2 for injecting soil solidifying agent, an extraction well 3, and a medicine injection well 4. The injection well 2 and the extraction well 3 are located outside the medicine injection well 4. The injection well 2 and the extraction well 3 are arranged in parallel, and the injection well 2 is located outside the extraction well 3 to ensure that the treatment range of the soil solidifying agent is large enough. The lower ends of the injection well and the medicine injection well are closed, and there are several water outlet holes on the well wall.

[0033] In addition, a submersible pump 6 is installed in the extraction well 3, and the water outlet of the submersible pump is connected to the sewage treatment equipment 5. The wastewater after in-situ leaching is pumped to the sewage treatment equipment 5 by the submersible pump for treatment, and the treated water is reused as the solvent of the leaching solution.

[0034] In terms of specific settings, the depth of the injection well is 0 - 0.5 m above the top of the contaminated soil layer, the depth of the extraction well is 0 - 0.5 m below the bottom of the contaminated soil layer, and the depth of the medicine injection well is not less than 0.5 m below the bottom of the contaminated soil layer.

[0035] According to Figure 3 , adopting the above system for in-situ leaching process, includes the following steps:

[0036] (1) Construct a cut-off curtain around the soil area to be repaired;

[0037] (2) Arrange several injection wells, extraction wells and medicine injection wells in the soil area to be repaired;

[0038] (3) Inject soil solidifying agent into the medicine injection well;

[0039] (4) Extract groundwater through the extraction well;

[0040] (5) Leaching: Inject leaching agent into the injection well, and after a period of time, extract the leaching solution through the extraction well and pump it to the water treatment equipment;

[0041] (6) Demolish the injection well, extraction well and medicine injection well to complete the repair;

[0042] In this embodiment, a cut-off curtain 1 is constructed around the soil area to be repaired, with a depth of not less than 1 m below the bottom of the contaminated soil layer. The cut-off curtain effectively blocks the migration of surrounding groundwater to the soil area to be repaired, avoids the influence of the groundwater flow field on the in-situ leaching effect, and at the same time, avoids the migration of leaching water to the external soil, resulting in pollution diffusion.

[0043] Select a number of points at the four corners and the central area of the soil area to be repaired, and arrange a set of injection wells 2, extraction wells 3 and medicine injection wells 4 at each point. The depth of the injection well 2 is 0 - 0.5 m from the top of the contaminated soil layer, the depth of the extraction well 3 is 0 - 0.5 m from the bottom of the contaminated soil layer, and the depth of the medicine injection well 4 is not less than 0.5 m from the bottom of the contaminated soil layer.

[0044] Next, inject a soil solidifying agent into the area to be repaired through the medicine injection well 4 to form a solidified layer at the bottom of the contaminated soil layer, increasing its hardness and waterproof effect, thereby slowing down the longitudinal migration effect of the leaching agent into the deeper soil layer.

[0045] Next, extract the groundwater in the area to be repaired through the submersible pump 6. Extracting the original groundwater in the site improves the migration effect of the leaching agent in the contaminated soil.

[0046] Inject the leaching agent into the injection well 2, and the leaching agent diffuses inside the contaminated soil under the action of gravity and the internal pressure of the injection well. Due to the similar pool structure formed by the solidified layer and the water-stop curtain 1, the contact between the leaching agent and the soil is more sufficient, improving the soil leaching effect.

[0047] After 2 - 5 days, extract the leaching liquid through the extraction well 3, and pump the extracted leaching liquid to the water treatment equipment 5 for wastewater treatment. The entire repair process is repeated 1 - 2 times.

[0048] Finally, remove the injection well 2, extraction well 3 and medicine injection well 4 to complete the entire process of in-situ soil leaching.

[0049] The preferred embodiments of the present invention have been specifically described above, but the present invention is not limited to the described embodiments. Those skilled in the art can also make various equivalent variations or substitutions without departing from the spirit of the present invention, and these equivalent variations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. An in-situ leaching repair system, characterized in that, Including: A cut-off curtain arranged around the soil to be repaired, injection and extraction units arranged at several points at the four corners and the central area of the soil area to be repaired, and a water treatment device arranged outside the soil area to be repaired and connected to the injection and extraction units. Each of the injection and extraction units includes an injection well, an extraction well, and a medicine injection well for injecting soil solidifying agent, and the injection well and the extraction well are located outside the medicine injection well.

2. The in-situ leaching repair system according to claim 1, characterized in that: Among them, The distance between two adjacent groups of injection and extraction units does not exceed 20 m; The injection well and the extraction well are arranged in parallel, and the injection well is located outside the extraction well; a submersible pump is arranged in the extraction well, and the water outlet of the submersible pump is connected to the sewage treatment device.

3. The in-situ leaching repair system according to claim 1, characterized in that: Among them, The depth of the injection well is 0 - 0.5 m above the top of the contaminated soil layer, the depth of the extraction well is 0 - 0.5 m below the bottom of the contaminated soil layer, and the depth of the medicine injection well is not less than 0.5 m below the bottom of the contaminated soil layer.

4. The in-situ leaching repair system according to claim 1, characterized in that: Among them, The lower ends of the injection well and the medicine injection well are closed, and a number of water outlet holes are provided on the well wall.

5. The in-situ leaching repair system according to claim 1, characterized in that: Among them, The cut-off curtain is constructed along the boundary of the soil area to be repaired, and the depth is not less than 1 m below the bottom of the contaminated soil layer.

6. An in-situ leaching and remediation process, characterized in that: By injecting soil solidifying agent into the bottom of the contaminated soil layer and cooperating with the cut-off curtain constructed around the soil area to be repaired, the longitudinal migration of the leaching agent is slowed down.

7. The in-situ leaching and restoration process according to claim 6, characterized in that, Including the following steps: (1) Construct a cut-off curtain around the soil area to be repaired; (2) Arrange a number of injection wells, extraction wells, and medicine injection wells in the soil area to be repaired; (3) Inject soil solidifying agent into the medicine injection well; (4) Extract groundwater through the extraction well; (5) Leaching: Inject leaching agent into the injection well, and after a period of time, extract the leaching solution through the extraction well and pump it to the water treatment device; (6) Demolish the injection well, extraction well, and medicine injection well to complete the repair.

8. The in-situ leaching repair process according to claim 7, characterized in that: Among them, The cut-off curtain is constructed along the boundary of the soil area to be repaired, and the depth is not less than 1 m below the bottom of the contaminated soil layer; the depth of the injection well is 0 - 0.5 m above the top of the contaminated soil layer, the depth of the extraction well is 0 - 0.5 m below the bottom of the contaminated soil layer, and the depth of the medicine injection well is not less than 0.5 m below the bottom of the contaminated soil layer. The injection well and the extraction well are located outside the medicine injection well, the injection well and the extraction well are arranged in parallel, and the injection well is located outside the extraction well; a submersible pump is arranged in the extraction well, and the water outlet of the submersible pump is connected to the sewage treatment device.

9. The in-situ leaching repair process according to claim 7, characterized in that: Among them, The form of the soil solidifying agent is liquid.

10. The in-situ leaching and remediation process according to claim 7, wherein: In the leaching step, after injecting the leaching agent into the injection well, extraction is carried out 2 - 5 days later, and the whole repair process is repeated 1 - 2 times.

Images