A coastal active anti-seepage composite barrier system and a method for controlling pollutants and seawater migration

Abstract

The present application relates to the field of environmental geotechnical engineering, and discloses a kind of active anti-seepage composite barrier system in coastal area and method for controlling pollutant and seawater migration, the monitoring data of seawater level and groundwater level in coastal area is acquired in real time, when seawater level is lower than groundwater level, groundwater downstream of pollutant migration is extracted and purified, and purified water is injected through injection well;When seawater level is higher than groundwater level, seawater intrusion occurs, purified groundwater is extracted to obtain purified water;The low-temperature purified water obtained by cooling the purified water is injected into aquifer through the active anti-seepage well and injection well arranged upstream of seawater intrusion respectively, the low-temperature purified water injected through the active anti-seepage well forms a reverse hydraulic gradient pointing to the direction of seawater migration, and the low-temperature purified water injected through the injection well is injected to maintain the balance of hydraulic gradient;The permeability of the soil body in the aquifer is reduced by using the injected low-temperature purified water, and the soil barrier is solidified to jointly block the migration of pollutants and seawater towards land.

Description

Technical Field

[0001] This invention relates to the field of environmental geotechnical engineering technology, and in particular to an active reverse osmosis composite barrier system for coastal areas and a method for controlling the migration of pollutants and seawater. Background Technology

[0002] Groundwater is a strategic resource supporting sustainable economic and social development, especially in coastal areas where uneven annual rainfall distribution due to climatic constraints makes groundwater the most stable and reliable water source for local production and daily life. However, with rapid urbanization and continuous industrial expansion, water demand is experiencing rigid growth, leading to excessive and concentrated extraction that has triggered large-scale seawater intrusion disasters. Simultaneously, intensive industrial and agricultural activities in coastal areas result in the continuous leakage of heavy metals, nitrogen-containing pollutants, and other contaminants, causing groundwater pollution to spread and pollution loads to rise year by year. The dual threat of seawater intrusion and groundwater pollution not only exacerbates the regional water resource crisis but also severely damages the ecological functions of aquifers, becoming a prominent bottleneck restricting the green development of coastal economic zones. Therefore, there is an urgent need to develop synergistic treatment technologies that can simultaneously block pollutant migration and curb saline intrusion.

[0003] Currently, the structures and design methods for land-based pollution barriers and seawater intrusion prevention are relatively mature. Among them, the most widely used method is to use anti-seepage walls to block the migration of pollutants and seawater. However, seawater intrusion actually occurs when the seawater level is higher than the groundwater level, forming a hydraulic gradient. This gradient causes damage such as salt swelling through soil seepage, which in turn causes continuous deterioration of the anti-seepage wall and increases the risk of pollution source leakage. There are few applications of adjusting hydraulic gradients and permeability in existing technologies. For example, Chinese patent CN114232663B discloses a variable permeability underground curtain and its construction method for preventing seawater intrusion and land-based pollution, and Chinese patent CN115611350B discloses a combined cutoff reactive wall for coastal groundwater environment management. When the seawater level is high and the groundwater level is low, seawater intrusion can still occur through seepage through the bottom or top structure. Artificial water injection is limited by the permeability of the aquifer soil, resulting in the extraction of some freshwater or the retention of saline water. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this invention is to provide an active reverse osmosis composite barrier system for coastal areas and a method for controlling the migration of pollutants and seawater. This system can actively regulate the hydraulic gradient and aquifer soil permeability using cooling water to control the migration direction of pollutants and seawater, thereby achieving active, coordinated, and efficient control of pollution plumes and seawater intrusion.

[0005] To achieve the above objectives, in a first aspect, the technical solution adopted by the present invention is as follows: a coastal active reverse osmosis composite barrier system, comprising: an active reverse osmosis well, located upstream of seawater intrusion and connected to a water pressure system, for injecting low-temperature water into the aquifer to form a reverse hydraulic gradient pointing in the direction of seawater intrusion and reducing soil permeability; an active reverse osmosis barrier, comprising a low-permeability solidified soil layer and a porous solidified soil layer arranged on the upstream and downstream sides of the active reverse osmosis well, for synergistically blocking pollutants and seawater; and a reaction filtration system, located near the pollution source, for extracting and purifying polluted water, comprising sequentially arranged from the center outwards... The system includes a filtration well, an adsorption layer for adsorbing trace organic matter, a reduction layer for reducing nitrates and chlorinated organic matter, a removal layer for removing phosphates and heavy metals, and a filtration layer for filtering suspended solids and colloids; an injection well, located between the porous solidified soil layer and the reaction filtration system, for injecting low-temperature water for reinjection to maintain hydraulic gradient balance; a groundwater cooling system, connected to the filtration well, for cooling the purified groundwater and transporting it to the active reverse osmosis well and the injection well; and a data acquisition and control system, connected to the injection well and the groundwater cooling system, for receiving real-time monitoring data and controlling the water pressure system for hydraulic gradient adjustment.

[0006] Furthermore, the active reverse osmosis well is a rigid permeable pipe with a single-sided opening facing the side where the seawater migrates, and its bottom penetrates the aquifer soil to below the pollution source.

[0007] Furthermore, the low-permeability solidified soil layer is designed with particle size according to the close packing theory and contains 5%–10% calcium-based bentonite, with a permeability coefficient of… k Less than 10 -9 cm / s.

[0008] Furthermore, the porous structure of the solidified soil layer is a lightweight foamed soil with a permeability coefficient of 10. -4 cm / s ~10 -7 Between cm / s.

[0009] Furthermore, the data acquisition and control system includes: Salt concentration sensor, volumetric water content sensor, temperature sensor and pore water pressure sensor installed along the direction of pollutant and seawater migration; Water quality sensors and flow meter sensors installed inside the filtration well; and, Rain gauges, relative humidity meters, and thermal radiation sensors installed on the ground enable real-time monitoring of water levels, salinity, and climate conditions.

[0010] Secondly, the technical solution adopted by this invention is as follows: a method for controlling pollutant and seawater migration based on the aforementioned active reverse osmosis composite barrier system in coastal areas, comprising: real-time acquisition of monitoring data on seawater level and groundwater level in coastal areas; based on the comparison results of seawater level and groundwater level, dividing the operation into two conditions: when the seawater level is lower than the groundwater level, activating the reaction filtration system to extract and purify the groundwater downstream of the pollutant migration, and reinjecting the purified water through an injection well; when the seawater level is higher than the groundwater level, determining that seawater intrusion has occurred, and activating the reaction filtration system. Groundwater is extracted and purified to obtain purified water; the purified water is then transported to a groundwater cooling system to be cooled to a set temperature to obtain low-temperature purified water; the low-temperature purified water is injected into the aquifer through active reverse osmosis wells and injection wells located upstream of seawater intrusion. The low-temperature purified water injected through the active reverse osmosis wells forms a reverse hydraulic gradient pointing in the direction of seawater migration, while the low-temperature purified water injected through the injection wells is reinjected to maintain the hydraulic gradient balance; the injected low-temperature purified water is used to reduce the permeability of the aquifer soil, working in conjunction with the solidified soil barrier to block the migration of pollutants and seawater towards the land.

[0011] Furthermore, low-temperature purified water is injected into the aquifer through an active reverse osmosis well located upstream of the seawater intrusion. The formula for calculating the injection volume Q1 of the active reverse osmosis well is as follows:

[0012] in, Q 1 represents the water injection volume of the active reverse osmosis well; The soil permeability coefficient at low temperatures; k Tr This refers to the soil permeability coefficient at room temperature. The viscosity of low-temperature groundwater; μ Tr The viscosity of groundwater at room temperature; h 2 represents the reverse osmosis point water level. h 1 represents the water level at the seawater intrusion point. L This is the distance between the reverse osmosis water point and the seawater intrusion water point; A The area where seepage occurs.

[0013] Furthermore, the active reverse osmosis system and the reaction filtration system are installed downstream of the pollutant migration and perpendicular to the migration path.

[0014] Furthermore, the active reverse osmosis composite barrier system is set up in the area where seawater intrusion has occurred. After adjusting the hydraulic gradient through the active reverse osmosis system, a soil seepage path is formed pointing in the direction of seawater intrusion. The water seepage carries away the salt accumulated in the soil to achieve soil desalination, thereby improving the salinized soil in the intrusion area.

[0015] Furthermore, when setting up a reaction filtration system, it should be ensured that the gradient of the permeability coefficient of the reaction layer increases from low to high along the direction of pollutant migration.

[0016] The present invention has the following advantages due to the adoption of the above technical solutions: The present invention provides a composite barrier composed of an active reverse osmosis well, a solidified soil barrier and a reaction filtration well. After removing pollutants by the reaction filtration well, it provides cooling water pressure to the active reverse osmosis well, thereby forming an active reverse hydraulic gradient pointing in the direction of seawater intrusion, reducing soil permeability, and achieving the effect of synergistic prevention and control of pollutant migration and diffusion and seawater intrusion. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the active reverse osmosis composite barrier system in the coastal area in an embodiment of the present invention; Figure 2 This is a top view schematic diagram of the active reverse osmosis composite barrier system in the coastal area in an embodiment of the present invention; Figure 3 This is a flowchart of a method for controlling pollutant and seawater migration based on an active reverse osmosis composite barrier system in coastal areas, as described in this invention. In the diagram: 1. Active reverse osmosis well, 2. Porous solidified soil barrier, 3. Low-permeability solidified soil barrier, 4. Seawater level, 5. Injection well, 6. Adsorption layer, 7. Reduction layer, 8. Removal layer, 9. Filter layer, 10. Pumping well, 11. Cooling system, 12. Monitoring and control system, 13. Pressure control system, 14. Direction of pollution source migration. Detailed Implementation

[0018] Studies have shown that low-temperature water injection can raise the groundwater level and reduce the permeability of aquifer soil, thereby inhibiting the migration of pollutants and seawater. If polluted groundwater is purified, cooled, and then reinjected, the hydraulic gradient can be adjusted by utilizing the rise in groundwater level and the reduction in permeability, thus increasing the barrier effect. Therefore, this invention provides an active reverse osmosis composite barrier system for coastal areas and a method for controlling the migration of pollutants and seawater. A reaction filtration system adsorbs pollutants from the polluted groundwater and pumps it out. After the extracted purified water is sent to a groundwater cooling system for cooling, it is injected upstream of the seawater intrusion zone through injection wells and the active reverse osmosis barrier system, forming an artificial reverse hydraulic gradient pointing in the direction of seawater intrusion, effectively preventing seawater intrusion. Simultaneously, the low-temperature injected water alters the permeability of the aquifer soil, synergistically strengthening the barrier performance. The injection pressure is precisely adjusted by a water pressure system, and the data acquisition and control system provides real-time feedback and optimizes system operation. This invention utilizes cooling water to regulate the hydraulic gradient and the permeability of the aquifer soil, thereby achieving proactive, coordinated, and efficient control of pollution plumes and seawater intrusion. It breaks through the limitations of traditional barriers that passively block pollution, and is particularly suitable for complex hydrogeological and pollution coexisting scenarios in coastal areas.

[0019] 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 accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] In one embodiment of the present invention, an active reverse osmosis composite barrier system for coastal areas is provided. This composite barrier combines active reverse osmosis technology, pollution remediation technology, and soil permeability regulation technology for coastal areas. It can actively regulate the hydraulic gradient and aquifer soil permeability using cooling water, thereby controlling the migration direction of pollutants and seawater, achieving active, coordinated, and efficient control of pollutant plume migration and seawater intrusion. In this embodiment, as... Figure 1 , Figure 2 As shown, the system includes: an active reverse osmosis well 1; an active reverse osmosis barrier composed of a low-permeability solidified soil layer 2 and a porous solidified soil layer 3; a reaction filtration system composed of an adsorption layer 6, a reduction layer 7, a removal layer 8, a filter layer 9, and a filtration well 10; an injection well 5; a monitoring and control device 12; a pressure control device 13; and a groundwater cooling system 11. Among them: Active reverse osmosis well 1 is located upstream of seawater intrusion and connected to water pressure system 13 to inject low temperature water into the aquifer to form a reverse hydraulic gradient pointing in the direction of seawater intrusion and reduce soil permeability. An active reverse osmosis barrier, as a solidified soil barrier, includes a low-permeability solidified soil layer 2 and a porous solidified soil layer 3 arranged on the upstream and downstream sides of the active reverse osmosis well 1, for synergistic blocking of pollutants and seawater. The reaction filtration system is located near the pollution source and is used to extract and purify polluted water. It includes a filtration well 10 arranged from the center outward, an adsorption layer 6 for adsorbing trace organic matter, a reduction layer 7 for reducing nitrates and chlorinated organic matter, a removal layer 8 for removing phosphates and heavy metals, and a filter layer 9 for filtering suspended solids and colloids. Injection well 5 is located between the porous solidified soil layer 3 and the reaction filtration system, and is used to inject low-temperature water for reinjection to maintain hydraulic gradient balance. The groundwater cooling system 11 is connected to the filtration well 10 and is used to cool the purified groundwater and transport it to the active reverse osmosis well 1 and the injection well 5. The data acquisition and control system 12 is connected to the water injection well 5 and the groundwater cooling system 11, and is used to receive real-time monitoring data and control the water pressure system 13 to perform hydraulic gradient adjustment.

[0022] In this embodiment, the filtration well 10 is used to purify polluted groundwater and provide a water source, the groundwater cooling system 11 reduces the water temperature, and the active reverse osmosis well 1 and the solidified soil barrier work together to form a hydraulic gradient pointing in the direction of seawater migration, reducing the permeability of the aquifer soil and jointly solving the problem of controlling the migration of pollutants and seawater.

[0023] In the above embodiments, the active reverse osmosis well 1 is a rigid permeable pipe with a single-sided opening facing the side where seawater migrates, and its bottom penetrates the aquifer soil to below the pollution source. In this embodiment, the bottom of the active reverse osmosis well 1 penetrates the aquifer soil to below the pollution source.

[0024] Among them, the active reverse osmosis well 1 is composed of a permeable pipe and an impermeable pipe connected together. When the system is running, the impermeable pipe provides water head pressure, and the cooling water flowing out of the permeable pipe forms a hydraulic gradient within the seawater intrusion range, reduces the permeability coefficient of the aquifer soil, and forces the seawater to migrate in the opposite direction, thereby achieving the purpose of preventing seawater intrusion.

[0025] In the above embodiments, the low-permeability solidified soil layer 2 is designed with particle size according to the close packing theory (e.g., the particle size distribution of the closest packing is determined by the Dinger-Funk (DF) equation), and should contain 5% to 10% calcium-based bentonite, with a permeability coefficient of k Less than 10 -9 cm / s. The porous, solidified soil layer 3 is a lightweight foamed soil with a permeability coefficient of at least 10. -4 cm / s ~10 -7 Between cm / s. Utilizing the different permeability coefficients, hydraulic seepage is formed pointing in a specific direction of seawater intrusion.

[0026] Among them, the wet density of the porous solidified soil layer 3 is controlled at 800~1100 kg / m³. 3 The curing agent can be selected from alkali-activated geopolymer materials, sulfoaluminate cement, and industrial waste modified cement, etc.

[0027] In this embodiment, the permeability coefficients of the low-permeability solidified soil layer 2 and the porous structure solidified soil layer 3 should differ by at least two orders of magnitude. When active reverse osmosis occurs, the cooling water is blocked by the low-permeability solidified soil barrier and will pass through the porous structure solidified soil barrier with higher permeability, thereby achieving active reverse osmosis pointing in the direction of seawater intrusion.

[0028] In the above embodiments, the reaction filtration system adopts a four-layer composite structure. Specifically, in this embodiment, along the pollutant migration direction 14, the first layer is a filter layer 9 composed of volcanic rock filter media and quartz sand, used to filter suspended solids, colloids, and some heavy metals; the second layer is a removal layer 8 composed of modified zeolite and iron phosphate slow-release agent, used to remove phosphates and heavy metals such as lead / cadmium from the pollution source; the third layer is a reduction layer 7 composed of zero-valent iron and biochar, used to reduce nitrates and chlorinated organic compounds; and the fourth layer is an adsorption layer 6 composed of activated carbon and nano-titanium oxide, used to adsorb benzene compounds and trace organic compounds such as pesticides. Through a physicochemical-biological multi-level synergistic mechanism, precise targeted removal of pollutants is achieved while ensuring long-term operation.

[0029] In the above embodiments, the data acquisition and control system 12 includes automatic data acquisition devices such as pore water pressure sensors, temperature sensors, salinity sensors, and water quality sensors, which are installed at locations sensitive to groundwater or seawater levels to collect data in real time for remote monitoring. Specifically, Salt concentration sensor, volumetric water content sensor, temperature sensor and pore water pressure sensor installed along the direction of pollutant and seawater migration; Water quality sensors and flow meter sensors are installed inside the filtration well 10; and, Rain gauges, relative humidity meters, and thermal radiation sensors installed on the ground enable real-time monitoring of water levels, salinity, and climate conditions.

[0030] In the above embodiment, the filtration well 10 is connected to the injection well 5 and the active reverse osmosis well 1 through pipelines. The reverse osmosis pressure is set by the seawater level feedback data. Water is pumped through the filtration well 10 to the groundwater cooling system 11 for cooling, and then transported to the active reverse osmosis well 1 for active reverse osmosis. Excess water is transported to the injection well for reinjection to maintain the stability of the hydraulic gradient on both sides of the solidified soil barrier.

[0031] In the above embodiments, the reverse hydraulic gradient of coastal water migration after adjustment by the active reverse osmosis system is between 0.25 and 0.35. The purified water is cooled to 4-8°C by the groundwater cooling system 11.

[0032] In the above embodiment, the water pressure system 13 receives instructions transmitted from the data acquisition and control system 12 to adjust the water head during active reverse osmosis and maintain the hydraulic gradient of continuous cooling water seeping into seawater.

[0033] The groundwater cooling system 11 is connected to the data acquisition and control system 12, and the groundwater cooling system 11 is also connected to the filtration well 10 through a pipeline. It receives instructions transmitted by the data acquisition and control system 12 to cool the filtration water and deliver it to the injection well 5 and the active reverse osmosis well 1.

[0034] In one embodiment of the present invention, a method for controlling pollutant and seawater migration using an active reverse osmosis composite barrier system in coastal areas is provided, based on the active reverse osmosis composite barrier system in coastal areas described in the above embodiments. In this embodiment, as... Figure 3 As shown, the method includes the following steps: 1) Real-time monitoring data of seawater and groundwater levels in coastal areas.

[0035] 2) Based on the comparison between seawater level and groundwater level, there are two operating conditions: when the seawater level is lower than the groundwater level, the reaction filtration system is activated to extract and purify the groundwater downstream of the pollutants, and the purified water is reinjected through the injection well; when the seawater level is higher than the groundwater level, it is determined that seawater intrusion has occurred, the reaction filtration system is activated to extract and purify the groundwater, and purified water is obtained.

[0036] 3) The purified water is transported to the groundwater cooling system 11 to be cooled to the set temperature to obtain low-temperature purified water.

[0037] 4) Low-temperature purified water is injected into the aquifer through active reverse osmosis well 1 and injection well 5 located upstream of seawater intrusion. The low-temperature purified water injected through active reverse osmosis well 1 forms a reverse hydraulic gradient pointing in the direction of seawater migration, and the low-temperature purified water injected through injection well 5 is reinjected to maintain the hydraulic gradient balance.

[0038] 5) The injected low-temperature purified water reduces the permeability of the aquifer soil and works in conjunction with the solidified soil barrier to block the migration of pollutants and seawater toward land.

[0039] In step 4) above, low-temperature purified water is injected into the aquifer through an active reverse osmosis well 1 located upstream of the seawater intrusion. The formula for calculating the injection volume Q1 in the active reverse osmosis well 1 is as follows:

[0040] in, Q 1 represents the water injection volume of active reverse osmosis well 1; The soil permeability coefficient at low temperatures; k Tr This refers to the soil permeability coefficient at room temperature. The viscosity of low-temperature groundwater; μ Tr The viscosity of groundwater at room temperature; h 2 represents the reverse osmosis point water level. h 1 represents the water level at the seawater intrusion point. L This is the distance between the reverse seepage point and the seawater intrusion point; A The area where seepage occurs.

[0041] In this embodiment, the ambient groundwater temperature Tr is determined by a sensor, and the soil permeability coefficient...k Tr The viscosity of groundwater at normal temperature was determined using traditional hydrogeological survey methods. μ Tr Determined by referring to a table. Reverse osmosis point water level. h 2 and the water level at the seawater intrusion point h 1, and the distance between the two points. L Determined through on-site conditions, including control i =0.25~0.35.

[0042] In the calculation, to maintain the balance of water resources and hydraulic gradient, the pumping volume is set as: pumping volume = reverse osmosis volume + injection volume. This is based on the location of seawater intrusion. h 1. Distance from the reverse osmosis point L and settings i The reverse osmosis point water level can be calculated. h 2. Simultaneously, based on the soil permeability coefficient at normal temperature k Tr and seepage area A The injection volume Q1 of the reverse osmosis well is obtained. Simultaneously, the water level at the reverse osmosis point should be equal to the water level in the injection well, meaning the injection volume Q1 of the reverse osmosis well is equal to the injection volume Q2 of the injection well. These are then added together to obtain the total pumping volume Q. Subsequently, the soil permeability coefficient at low temperatures can be obtained. The viscosity of groundwater at room temperature is half that of soil at normal temperature. This viscosity can be obtained through field investigation and table reference. μ Tr and viscosity of low-temperature groundwater Therefore, the corresponding cooling temperature Tl can be obtained.

[0043] In a preferred embodiment, the active reverse osmosis system and the reactive filtration system are installed downstream of the pollutant migration path and perpendicular to it. Specifically, the active reverse osmosis well 1 and the solidified soil barrier can be located at the seawater intrusion interface, while the reactive filtration system is located downstream of the pollutant migration path.

[0044] In a preferred embodiment, the active reverse osmosis composite barrier system is set in the area where seawater intrusion has occurred. After adjusting the hydraulic gradient through the active reverse osmosis system, a soil seepage path is formed pointing in the direction of seawater intrusion. The water seepage carries away the salt accumulated in the soil to achieve soil desalination, thereby improving the salinized soil in the intrusion area.

[0045] In a preferred embodiment, the data acquisition and control system 12 monitors the water quality of the reaction filtration water in real time. If the concentration of pollutants in the water after the reaction is abnormal, a secondary chemical cleaning or substrate replacement is initiated in a timely manner.

[0046] In a preferred embodiment, when setting up the reaction filtration system, the permeability coefficient gradient of the reaction layer is ensured to increase from low to high along the direction of pollutant migration to avoid flow interruption.

[0047] In a preferred embodiment, a geotextile gradient filter layer may be provided between the reaction layers to prevent fine particle migration from causing mixed-layer contamination.

[0048] In summary, the composite barrier of this invention consists of an active reverse osmosis well 1, a solidified soil barrier, a filtration well 10, a water injection well 5, a data acquisition and control system 12, a water pressure system 13, and a groundwater cooling system 11. The filtration well 10 extracts and adsorbs pollutants from the groundwater. The extracted purified water is then sent to the groundwater cooling system 11 for cooling treatment, and then injected into the upstream location of the seawater intrusion zone through the water injection well 5 and the active reverse osmosis well 1, forming an artificial reverse hydraulic gradient pointing in the direction of seawater intrusion, effectively preventing seawater intrusion. Simultaneously, the low-temperature injected water alters the permeability of the aquifer soil, synergistically enhancing the barrier performance with the solidified soil barrier, thereby achieving active, coordinated, and efficient control of pollutant plume migration and seawater intrusion. This invention overcomes the limitations of passive regulation in traditional antifouling barriers and seawater intrusion barriers, significantly improving active response and automatic adjustment capabilities. It is suitable for coastal areas with strict prevention and control requirements, or complex hydrogeological scenarios where pollution coexists.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite barrier system for active reverse osmosis in coastal areas, characterized in that, include: An active reverse osmosis well (1) is set up upstream of the seawater intrusion and connected to the water pressure system (13) to inject low-temperature water into the aquifer to form a reverse hydraulic gradient pointing in the direction of seawater intrusion and reduce soil permeability. An active reverse osmosis barrier includes a low-permeability solidified soil layer (2) and a porous solidified soil layer (3) arranged on the upstream and downstream sides of an active reverse osmosis well (1) to synergistically block pollutants and seawater. The reaction filtration system is set near the pollution source and is used to extract and purify polluted water. It includes a filtration well (10) arranged from the center outward, an adsorption layer (6) for adsorbing trace organic matter, a reduction layer (7) for reducing nitrates and chlorinated organic matter, a removal layer (8) for removing phosphates and heavy metals, and a filter layer (9) for filtering suspended solids and colloids. Water injection wells (5) are arranged between the porous solidified soil layer (3) and the reaction filtration system to inject low-temperature water for reinjection to maintain hydraulic gradient balance. The groundwater cooling system (11) is connected to the filtration well (10) and is used to cool the purified groundwater and transport it to the active reverse osmosis well (1) and the injection well (5). The data acquisition and control system (12) is connected to the water injection well (5) and the groundwater cooling system (11) to receive real-time monitoring data and control the water pressure system (13) to perform hydraulic gradient adjustment.

2. The active reverse osmosis composite barrier system for coastal areas as described in claim 1, characterized in that, The active reverse osmosis well (1) is a rigid permeable pipe with a single-sided opening facing the side of seawater migration, and its bottom penetrates the aquifer soil to below the pollution source.

3. The active reverse osmosis composite barrier system for coastal areas as described in claim 1, characterized in that, The low-permeability solidified soil layer (2) is designed with particle size according to the close packing theory and contains 5% to 10% calcium-based bentonite with a permeability coefficient of k Less than 10 - 9 cm / s.

4. The active reverse osmosis composite barrier system for coastal areas as described in claim 1, characterized in that, The porous solidified soil layer (3) is a lightweight foamed soil with a permeability coefficient of 10. -4 cm / s ~10 -7 Between cm / s.

5. The active reverse osmosis composite barrier system for coastal areas as described in claim 1, characterized in that, The data acquisition and control system (12) includes: Salt concentration sensor, volumetric water content sensor, temperature sensor and pore water pressure sensor installed along the direction of pollutant and seawater migration; Water quality sensors and flow meter sensors are installed inside the filtration well (10); and, Rain gauges, relative humidity meters, and thermal radiation sensors installed on the ground enable real-time monitoring of water levels, salinity, and climate conditions.

6. A method for controlling pollutant and seawater migration based on the active reverse osmosis composite barrier system in coastal areas according to any one of claims 1 to 5, characterized in that, include: Real-time monitoring data of seawater and groundwater levels in coastal areas; Based on the comparison between seawater level and groundwater level, there are two operating conditions: when the seawater level is lower than the groundwater level, the reaction filtration system is activated to extract and purify the groundwater downstream of the pollutants, and the purified water is reinjected through the injection well; when the seawater level is higher than the groundwater level, it is determined that seawater intrusion has occurred, the reaction filtration system is activated to extract and purify the groundwater, and purified water is obtained. The purified water is transported to a groundwater cooling system to be cooled to a set temperature, resulting in low-temperature purified water. Low-temperature purified water is injected into the aquifer through active reverse osmosis wells and injection wells located upstream of seawater intrusion. The low-temperature purified water injected through the active reverse osmosis wells forms a reverse hydraulic gradient pointing in the direction of seawater migration, while the low-temperature purified water injected through the injection wells is reinjected to maintain the hydraulic gradient balance. The injected low-temperature purified water reduces the permeability of the aquifer soil, working in conjunction with the solidified soil barrier to block the migration of pollutants and seawater toward land.

7. The method for controlling pollutant and seawater migration as described in claim 6, characterized in that, Low-temperature purified water is injected into the aquifer through active reverse osmosis wells located upstream of seawater intrusion. The formula for calculating the injection volume Q1 of the active reverse osmosis wells is as follows: in, Q 1 represents the water injection volume of the active reverse osmosis well; This refers to the soil permeability coefficient at low temperatures. k Tr This refers to the soil permeability coefficient at room temperature. The viscosity of low-temperature groundwater; μ Tr The viscosity of groundwater at room temperature; h 2 represents the water level at the reverse osmosis point. h 1 represents the water level at the seawater intrusion point. L This is the distance between the reverse osmosis water point and the seawater intrusion water point; A The area where seepage occurs.

8. The method for controlling pollutant and seawater migration as described in claim 6, characterized in that, The active reverse osmosis system and the reaction filtration system are installed downstream of the pollutant migration and perpendicular to the migration path.

9. The method for controlling pollutant and seawater migration as described in claim 6, characterized in that, The active reverse osmosis composite barrier system is set up in the area where seawater intrusion has occurred. After adjusting the hydraulic gradient through the active reverse osmosis system, a soil seepage path is formed pointing in the direction of seawater intrusion. The water seepage carries away the salt accumulated in the soil to achieve soil desalination, thereby improving the salinized soil in the intrusion area.

10. The method for controlling pollutant and seawater migration as described in claim 6, characterized in that, When setting up a reaction filtration system, the permeability gradient of the reaction layer should be ensured to increase from low to high along the direction of pollutant migration.

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