In-situ purification integrated device for VOCs in groundwater and application method

Abstract

The present invention discloses an in-situ purification integrated device for VOCs in groundwater and an application method, which relates to the technical field of in-situ remediation of soil and groundwater. The device includes an in-situ air stripping-aeration-agent dosing integrated pneumatic pump, a groundwater extraction well, an agent dosing pipe, a ground agent dosing device, a pneumatic pump access pipe, a ground tail gas treatment device, a fan, and a vapor extraction device. By connecting the in-situ air stripping-aeration-agent dosing integrated pneumatic pump with the ground tail gas treatment device, the present invention realizes the recycling of tail gas within the system, reduces the high dependence on tail gas treatment processes, lowers the equipment operation, maintenance, and detection costs. The tail gas circulates within the system, avoiding direct emission of tail gas to the outside world, greatly reducing the potential pollution risk to the surrounding environment, realizing a more environmentally friendly groundwater purification process, and reducing the occurrence probability of environmental problems and related environmental incidents caused by tail gas emissions.

Description

Technical Field

[0001] The present invention relates to the technical field of in-situ remediation of soil and groundwater, and specifically to an integrated device for in-situ purification of VOCs in groundwater and an application method thereof. Background Technique

[0002] In the face of contaminated underground aquifers, especially those contaminated by volatile organic pollutants (VOCs) such as petroleum hydrocarbons, chlorinated hydrocarbons, and benzene series, in-situ treatment technologies such as groundwater pumping treatment and groundwater aeration treatment are widely used due to their significant treatment effects and economic advantages.

[0003] The groundwater pumping treatment technology arranges groundwater pumping wells in the target aquifer, pumps the contaminated groundwater to the ground with the help of a water pump, and then uses various treatment technologies to purify it for use or re-inject it underground. Among them, the air stripping + activated carbon adsorption process is widely used in the sewage treatment process after the groundwater pumping treatment process. For example, Patent CN118652016B discloses a contaminated groundwater pumping treatment device and treatment process. The treatment device includes a base and a pumping component, a stripping and deodorizing component, and an electrocatalytic oxidation component arranged on the base. The pumping component is responsible for pumping the sewage accumulated in the underground well into the stripping and deodorizing component. The stripping and deodorizing component converts the odor pollutants in the sewage into gas phase and discharges them from the device. The electrocatalytic oxidation component oxidizes and decomposes pollutants such as benzene, carbon tetrachloride, chlorobenzene, chloroform, and 4-chlorodiphenyl ether in the sewage into small molecule substances, so that the pollutants are discharged from the device, thereby realizing the pumping treatment of contaminated groundwater. The device structure of this invention is reasonably designed, can effectively remove the odor substances in the sewage, prevent the further deterioration of the surrounding environment caused by the contaminated groundwater, and at the same time use the electrocatalytic oxidation component to oxidize and decompose specific pollutants, improving the safety of sewage discharge.

[0004] As an in-situ remediation technology for treating organic pollution in soil and groundwater, the groundwater aeration technology injects pressurized air below the saturated aquifer, prompting organic pollutants to be transformed into volatile pollutants through mass transfer between phases (dissolution, volatilization, desorption, biodegradation, etc.), and migrating with the air flow to the vadose zone, where they are then collected by other air extraction devices and sent to surface gas treatment equipment. In the early stage, the application scenario of the groundwater aeration technology was greatly restricted by the formation conditions because a certain number of extraction wells needed to be arranged in the vadose zone above the saturated layer to collect and treat the organic vapor generated by groundwater aeration. To improve its adaptability, the in-well aeration method was developed. That is, after groundwater flows into the well and undergoes stripping aeration in the well, the volatilized vapor is extracted by a negative pressure fan and sent to the above-ground tail gas treatment device for treatment. The preliminarily purified groundwater then undergoes further mass transfer with the groundwater around the well through concentration gradients and other effects. For example, the invention patent CN109047302B discloses an in-situ aeration remediation method for VOCs-polluted groundwater in low-permeability areas. Based on the surfactant-enhanced aeration remediation method, the point-adjustable hydraulic fracturing technology is used to perform multi-point hydraulic fracturing on the low-permeability pollution area, generating a large number of artificial fractures in this area. At the same time, the pressure solution used for fracturing is a surfactant solution, which enhances the gas permeability of the low-permeability pollution area and the desorption ability of pollutants from fine-grained soil, effectively solving the problem of difficult remediation in low-permeability pollution areas. It is the synergistic effect of the hydraulic fracturing technology and the surfactant enhancement on the basis of traditional groundwater aeration that enhances the desorption of pollutants in low-permeability formations and improves the treatment effect.

[0005] However, although the above inventions have improved the application effect of groundwater pumping + aeration and in-situ groundwater aeration technologies in the field of groundwater remediation to a certain extent, they all have the problem of qualified tail gas discharge. In the above remediation processes, the tail gas treatment device cannot achieve an internal gas cycle. After the polluted gas is treated by the tail gas treatment device, it needs to be discharged. This requires the tail gas to meet the relevant emission standards for qualified discharge, which places high requirements on the tail gas treatment process and increases the costs of equipment operation, maintenance, and detection. Therefore, it is necessary to propose an in-situ purification integrated device and application method for VOCs in groundwater to solve the problems in the existing technology. Summary of the Invention

[0006] The purpose of the present invention is to make up for the deficiencies of the existing technology by providing an in-situ purification integrated device and application method for VOCs in groundwater. It can realize the recycling of tail gas, reduce the high dependence on the tail gas treatment process, lower the costs of equipment operation, maintenance, and detection, avoid directly discharging tail gas to the outside world, and greatly reduce the potential pollution risk to the surrounding environment.

[0007] To solve the above technical problems, the present invention provides the following technical solution: an in-situ purification integrated device for VOCs in groundwater. The device includes an in-situ air stripping-aeration-reagent dosing integrated pneumatic pump, a groundwater extraction well, a reagent dosing pipe, a ground reagent dosing device, a pneumatic pump access pipe, a ground tail gas treatment device, a fan, and a gas extraction device. The in-situ air stripping-aeration-reagent dosing integrated pneumatic pump is driven by gas, and its air inlet end is connected to the fan through a pipeline. The fan is connected to the ground tail gas treatment device through a pipeline and is used to receive the treated tail gas as a power source. One end of the reagent dosing pipe is connected to the ground reagent dosing device, and the other end of the reagent dosing pipe is communicated with the in-situ air stripping-aeration-reagent dosing integrated pneumatic pump. The reagent dosing rate is controlled by the opening and closing size of the solenoid valve in the ground reagent dosing device, and the control signal of the solenoid valve is generated and transmitted by a computer program. The pneumatic pump access pipe is connected to the in-situ air stripping-aeration-reagent dosing integrated pneumatic pump and is connected to a high-temperature air source, and a flow regulating valve is provided on the pneumatic pump access pipe. The ground tail gas treatment device is connected to each extraction well pipe through a pipeline, and an activated carbon adsorption tank is provided inside. Columnar activated carbon with a particle size of 3-5 mm is filled in the activated carbon adsorption tank, and the gas treated by it can be pressurized and heated by the fan and then pumped back into the in-situ air stripping-aeration-reagent dosing integrated pneumatic pump.

[0008] Further, an air access end is provided at the bottom end of the in-situ air stripping-aeration-reagent dosing integrated pneumatic pump. Inside the in-situ air stripping-aeration-reagent dosing integrated pneumatic pump, a negative pressure suction section, a throat pipe gradual change section, and a high-pressure jet mixing section are sequentially arranged from bottom to top. A liquid phase suction port is provided on the outer surface of the in-situ air stripping-aeration-reagent dosing integrated pneumatic pump, and the liquid phase suction port is communicated with the negative pressure suction section. A pipeline connector one is installed at the left end of the in-situ air stripping-aeration-reagent dosing integrated pneumatic pump, and the pipeline connector one is connected to the reagent dosing pipe. A pipeline connector two is installed at the bottom end of the air access end, and the pipeline connector two is connected to the pneumatic pump access pipe. A one-way valve is provided inside the pipeline connector one, and the one-way valve allows the reagent to flow unidirectionally into the mixing chamber to prevent the gas-liquid mixture in the mixing chamber from flowing back to the reagent dosing pipe.

[0009] Furthermore, the groundwater extraction well is a double-layer special stainless steel well pipe, the inner layer is a 304 stainless steel slit pipe, the slits are spirally distributed and the slit width is 0.1-0.5mm, and the outer layer is a stainless steel wire mesh structure. The two layers are filled with gravel and quartz sand with a particle size of 2-3mm. An intermediate barrier is provided in the middle of the groundwater extraction well, which divides the well pipe into two parts, the upper and lower parts. The intermediate barrier is made of rubber and fits tightly to the inner wall of the well pipe. The integrated pneumatic pump is installed in the lower layer of the well pipe, and a filter is provided on the upper layer of the groundwater extraction well. The filter is made of stainless steel and has a mesh diameter of 0.1-0.5mm. The filter is connected to the gas phase extraction device 8 through a pipeline.

[0010] Furthermore, the thickness of the intermediate barrier is 5-10 cm, and annular sealing grooves are provided on the upper and lower surfaces thereof, with sealing rings installed in the sealing grooves. The thickness of the filter is 10-15 cm, and the filter is made of multiple layers of stainless steel wire mesh. The mesh diameter of each layer of wire mesh gradually decreases from near the inside of the well pipe to the outside.

[0011] Furthermore, an anti-corrosion protective layer is provided on the outside of the groundwater extraction well, and the anti-corrosion protective layer is an epoxy resin coating with a thickness of 0.5-1.5 mm.

[0012] An application method of an integrated in-situ purification device for VOCs in groundwater, the method comprising the following steps:

[0013] Start the fan and gas phase extraction device to extract the volatilized pollutants in the groundwater to the surface exhaust gas treatment device. The treated exhaust gas is pressurized and heated by the fan and then transported to the in-situ gas lift-aeration-drug dosing integrated pneumatic pump as a power source. At the same time, the automatic pressure replenishment device of the fan extraction pipeline extracts ambient air at startup, automatically closes after the air volume is balanced, and starts the exhaust gas internal circulation. During the ambient air extraction stage, the fan speed is 1000-1500rpm. When switching to the exhaust gas internal circulation, the fan speed is adjusted to 800-1200rpm;

[0014] High-pressure gas enters the pneumatic pump to generate negative pressure, and the groundwater in the lower layer of the extraction well is extracted to the upper layer through the air lift extraction pipe. The groundwater is mixed with the gas at high speed in the pump body and then ejected from the nozzle at high speed to achieve aeration in the well. At the same time, the filter on the upper layer of the well pipe intercepts water vapor, and the pollutants are evaporated and extracted by the exhaust device and then enter the tail gas treatment device for recycling. The water circulates under gravity and slightly positive pressure. During the aeration process in the well, the gas flow of the pneumatic pump is adjusted to make the rising flow rate of the water in the well 1-3m / s;

[0015] According to the repair requirements, prepare the repair agent in the ground agent dosing device. Adjust the agent dosing rate by controlling the opening and closing size of the solenoid valve. The agent dosing can be carried out synchronously with aeration, that is, the agent is injected into the pneumatic pump under the action of negative pressure through the dosing pipe, mixed with groundwater and air, and then sprayed out and infiltrated back into the original formation under the action of hydraulic and air pressure to achieve agent dosing and mixing. When carried out synchronously, the ratio of the agent flow rate in the agent dosing pipe to the gas flow rate in the pneumatic pump is 1:5 - 1:10. It can also be carried out separately, that is, close the valve between the tail gas device and the pneumatic pump, and the fan extracts ambient air and injects it into the well. The groundwater and the agent are pumped to the upper sieve tube section and then quickly discharged under pressure to accelerate the agent dosing. When carried out separately, the flow rate of the ambient air extracted by the fan is 1.2 - 1.5 times the gas flow rate during normal tail gas circulation.

[0016] Furthermore, when carrying out in-well aeration, control the access amount of high-temperature air by adjusting the flow regulating valve on the access pipe of the pneumatic pump to maintain the aeration temperature at 30 - 50°C. The access temperature of the high-temperature air is 100 - 200°C. During the circulation process of the groundwater, each time after aeration and circulation treatment, the residence time in the aquifer is 2 - 5 hours. And after each circulation treatment, detect the VOCs concentration in the groundwater. When the concentration is reduced below the set threshold, stop the purification treatment in this area.

[0017] Even further, during the process of separate agent dosing, when the agent is an oxidation-type agent, the agent should complete at least 1 - 2 cycles in the lithologic formation around the injection well to ensure uniform and sufficient agent dosing. When the agent is a reduction-type agent, add an appropriate amount of acidic regulator to the groundwater extraction well before dosing to adjust the pH value of the groundwater to 3 - 5 to improve the reduction reaction efficiency. During the whole application process, regularly regenerate the activated carbon adsorption tank in the ground tail gas treatment device. The regeneration period is 1 - 3 months. The regeneration method is hot air purging, the hot air temperature is 120 - 150°C, and the purging time is 2 - 4 hours.

[0018] Even further, before starting the device, pre-treat the formation around the groundwater extraction well, including injecting a cleaning agent. The cleaning agent uses a surfactant solution with a concentration of 0.5% - 2%. During the application process, real-time monitor the change of the groundwater level and adjust the operating parameters of the fan and the pneumatic pump according to the water level change. During the agent dosing process, select appropriate agent types and dosing sequences according to the water quality and pollutant components of the groundwater. When there are multiple VOCs pollutants in the water, first dose the special agent for the main pollutant, and then dose the auxiliary agent.

[0019] Compared with the prior art, the in-situ purification integrated device and application method for VOCs in groundwater have the following beneficial effects:

[0020] I. By connecting the in-situ air stripping - aeration - chemical dosing integrated pneumatic pump to the ground tail gas treatment device, the tail gas purified by the tail gas treatment device is pressurized and heated by a fan and then pumped back into the pneumatic pump as a power source, realizing the recycling of the tail gas within the system, reducing the high dependence on the tail gas treatment process, thereby reducing the equipment operation, maintenance and detection costs. Since the tail gas circulates within the system, the direct emission of tail gas to the outside is avoided, greatly reducing the potential pollution risk to the surrounding environment, realizing a more environmentally friendly groundwater purification process, meeting the environmental protection requirements, and reducing the occurrence probability of environmental problems and related environmental incidents caused by tail gas emissions.

[0021] II. The chemical dosing pipe of the present invention is connected to the ground chemical dosing device, which enables precise adjustment of the chemical dosing amount according to the actual situation such as the pollution degree of groundwater and the characteristics of the aquifer during the repair process, realizing precise repair. The chemical dosing can be carried out synchronously with aeration. At this time, the chemical agent is mixed with groundwater and air in the pipeline and then sprayed, and infiltrates back into the original formation under the dual action of hydraulic and air pressure, realizing the dosing and mixing of the chemical agent under the action of hydraulic circulation. It can also be carried out separately. The environmental air is extracted by a fan and injected into the well, and the groundwater and the chemical agent are pumped to the upper screen pipe section and then quickly discharged, accelerating the chemical dosing process. This diversified dosing mode can be flexibly selected according to the actual repair requirements, realizing the synergistic effect of aeration flushing and treatment methods such as oxidation / reduction / microorganisms, and providing a more comprehensive and effective groundwater purification solution for different pollution scenarios and repair targets.

[0022] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a schematic diagram of the overall structure of the in-situ purification integrated device for VOCs in groundwater;

[0025] Figure 2 It is a schematic diagram of the structure of the in-situ air stripping - aeration - chemical dosing integrated pneumatic pump.

[0026] In the figure: 1. In-situ air stripping - aeration - chemical dosing integrated pneumatic pump; 101. Air access end; 102. Negative pressure suction section; 103. Throat tube gradual change section; 104. High-pressure jet mixing section; 105. Liquid phase suction port; 106. Pipeline connector 1; 107. Pipeline connector 2; 2. Groundwater extraction well; 201. Intermediate barrier; 202. Filter screen; 3. Chemical dosing pipe; 4. Ground chemical dosing device; 5. Pneumatic pump access pipe; 6. Ground tail gas treatment device; 7. Fan; 8. Gas phase extraction device. Specific implementation mode

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] Embodiment 1: Pumping and aeration of groundwater

[0029] First, carefully assemble the device for in-situ purification of VOCs in groundwater. The groundwater extraction well 2 uses a customized stainless steel double-layer well pipe. The slits of the internal 304 stainless steel slotted pipe are in a carefully designed spiral shape, with the width strictly adjusted to 0.3 mm, the slit spacing accurately set to 8 mm, the length determined to be 10 cm, and adjacent slits staggered by 45 degrees to ensure that groundwater can enter the extraction pipe efficiently and evenly. The external stainless steel wire mesh structure is tightly wrapped, and quartz sand with a particle size of 2.5 mm that has been strictly screened and cleaned is filled between the two layers to effectively prevent impurities from mixing into the groundwater and affecting the treatment effect. The intermediate barrier 201 is made of high-quality rubber with a thickness of 5 mm and fits tightly with the inner wall of the well pipe. High-elastic rubber gaskets with a Shore hardness of 55 degrees are installed in the annular sealing grooves on the upper and lower surfaces to ensure the water impermeability of the intermediate barrier 201 and perfectly separate the upper and lower parts of the well pipe. The upper filter screen 202 is composed of multiple layers of 5 mm thick stainless steel wire meshes stacked together, and the mesh apertures are 0.5 mm, 0.3 mm, and 0.1 mm from the inside to the outside in sequence, forming an effective aperture gradient, which can intercept the high-speed ejected water vapor to the greatest extent and prevent the water vapor from entering the tail gas treatment system.

[0030] Start the fan 7 and the gas phase extraction device 8. The initial rotation speed of the fan 7 is set to 1200 rpm, and the polluted gas volatilized from the groundwater is extracted to the ground tail gas treatment device 6. The activated carbon adsorption tank in the ground tail gas treatment device 6 starts to work efficiently, strongly adsorbing and purifying the polluted gas. The activated carbon adsorption tank is filled with activated carbon with a particle size of 4 mm that has been specially activated and has a specific surface area of 1200 m 2Cylindrical activated carbon of / g, with a gas distribution plate at the bottom. The ventilation holes have a diameter of 3 mm and are arranged in an equilateral triangle. At the same time, the automatic pressure compensation device of the extraction pipeline of the fan 7 extracts ambient air. When the system air volume monitored by the air volume sensor with an accuracy of ±5 m 3 / h reaches balance, the extraction of ambient air is automatically closed, the rotational speed of the fan 7 is adjusted to 1000 rpm, and the tail gas internal circulation is started.

[0031] The tail gas treated by the ground tail gas treatment device 6 is pressurized to 0.3 MPa and heated to 80 °C by the booster fan 7, and then transported to the in-situ air stripping-aeration-reagent dosing integrated pneumatic pump 1. The high-pressure gas enters the pneumatic pump to generate negative pressure, and the groundwater in the lower layer of the groundwater extraction well 2 is extracted to the upper layer through the air stripping extraction pipe. By adjusting the gas flow regulating valve of the pneumatic pump, the upward flow velocity of the water in the well is accurately maintained at 1.5 m / s.

[0032] The upper-layer filter screen 202 of the well pipe intercepts the high-speed ejected water vapor to prevent it from being sucked into the ground tail gas treatment device 6 by the gas-phase extraction device 8. After the pollutants volatilize, they are pumped away by a high-efficiency vacuum pump with an extraction rate of 8 m 3 / min and a vacuum degree of up to -0.085 MPa and enter the tail gas treatment device for re-circulation treatment. Under the action of gravity and slightly positive pressure, the water seeps out from the upper-layer sieve tube, migrates downward under the action of gravity, and enters the lower-layer sieve tube under the action of the water head to form a stable cycle. The slightly positive pressure monitors the pressure through a pressure sensor with an accuracy of ±0.01 MPa set on the upper layer of the well pipe. In this process, every time after aeration and circulation treatment, the residence time of the groundwater in the aquifer is 3 hours to fully carry out mass transfer and pollutant removal. At the same time, multiple temperature sensors and water quality monitoring points with an accuracy of ±0.5 °C are set at different depths of the aquifer to comprehensively monitor the temperature and water quality changes in real time, so as to adjust the operation parameters accurately in time.

[0033] During the operation process, the change of the groundwater level is accurately monitored in real time through a water level sensor with an accuracy of ±0.05 m installed in the well. If the water level drops by more than 0.5 m, the power of the fan 7 and the pneumatic pump is appropriately reduced to prevent excessive extraction of groundwater. At the same time, the concentration of VOCs in the groundwater is detected every 2 hours by gas chromatography regularly to observe the purification effect. If it is found that the purification effect is not ideal, the parameters such as the gas flow of the pneumatic pump and the aeration temperature can be further optimized. For example, by finely changing the intake pressure of the pneumatic pump between 0.2 - 0.4 MPa, or accurately adjusting the aeration temperature between 70 - 90 °C, to ensure that the purification of groundwater reaches the expected goal. In addition, the connection conditions of each component of the device are checked every quarter, such as checking the sealing performance by pressure testing the pipe joints, and checking the operation stability of the pneumatic pump every month to timely discover and solve potential problems.

[0034] Through the above-mentioned precise device design and strict operation control, efficient groundwater aeration purification is achieved. The tail gas internal circulation system effectively reduces operating costs and avoids environmental pollution caused by tail gas emissions. The stable groundwater circulation and optimized aeration process enable the VOCs in the aquifer to be continuously reduced, thereby improving the groundwater quality. Accurate monitoring and adjustment measures ensure the stable operation of the system, extend the service life of the equipment, and provide a reliable and cost-effective solution for in-situ groundwater purification.

[0035] Example 2: Adding reagents while aerating to achieve the coordinated use of multiple technologies

[0036] According to the pollution situation of groundwater, select appropriate remediation agents. When the main pollutants in the water are benzene series, prepare an appropriate amount of potassium permanganate as an oxidizing agent and add it to the agent storage tank of the ground agent dosing device 4. The agent storage tank is made of stainless steel, and the inner wall is coated with a high-quality anti-corrosion coating to prevent the agent from corroding the tank body. The storage tank is equipped with an agitator, and the agitator speed can be adjusted between 50-100rpm to ensure that the agent is uniform. The metering pump in the ground agent dosing device 4 uses a high-precision metering pump with a flow accuracy of ±1%. It is connected to the agent storage tank and the agent dosing pipe 3, and the inlet of the agent dosing pipe 3 in the integrated pneumatic pump is located at the bottom of the gas and liquid mixing chamber. The stainless steel one-way valve and the polytetrafluoroethylene inclined baffle at the inlet form an anti-backflow structure that has been installed. The one-way valve has good sealing performance and the baffle surface is smooth to prevent the mixture from flowing back.

[0037] According to the steps of Example 1, the fan 7, the gas phase extraction device 8 and the ground exhaust gas treatment device 6 are started to put the system into the exhaust gas internal circulation state, the speed of the fan 7 is stabilized at 1000 rpm, and the pneumatic pump is ready to receive power source to work.

[0038] When the agent and aeration are selected to be carried out simultaneously, the solenoid valve in the agent dosing device is started. According to the computer program setting, the opening and closing size of the solenoid valve is adjusted to make the ratio of the agent flow rate in the agent dosing pipe 3 to the gas flow rate in the pneumatic pump be 1:8. While the fan 7 extracts the polluted gas to the exhaust gas treatment device, the agent is injected into the pneumatic pump through the dosing pipe under the action of negative pressure. In the pneumatic pump, the agent is fully mixed with the groundwater and air under the action of negative pressure. Then, the mixed gas-liquid mixture is ejected from the nozzle at high speed. The ejected agent, groundwater and air mixture seeps back into the original formation under the dual action of hydraulic force and air pressure. Under the action of hydraulic circulation, efficient agent addition and mixing are achieved, and aeration treatment is carried out at the same time. In this process, the mixing time of the agent in the groundwater and air is not less than 10 minutes to ensure that the oxidation reaction is fully carried out. At the same time, multiple redox potential sensors with an accuracy of ±10mV are set at different positions to monitor the progress of the redox reaction so as to accurately adjust the agent dosage.

[0039] If the reagent is added separately, close the valve between the exhaust device and the pneumatic pump, start the fan 7 to extract ambient air, and at this time increase the speed of the fan 7 to 1300rpm, inject the groundwater and the reagent into the well and pump them to the upper sieve section. Then, under the action of pressure, the mixed reagent and groundwater are quickly discharged from the well pipe, accelerating the reagent addition process. When the reagent is a reducing agent, add an appropriate amount of acid regulator to the groundwater extraction well 2 before addition, and monitor the pH value changes in real time through a pH sensor with an accuracy of ±0.1pH to ensure that the groundwater pH value is accurately adjusted to 4 to improve the efficiency of the reduction reaction.

[0040] During the coordinated treatment process of reagent addition and aeration, online monitors are continuously used to monitor the changes in VOCs concentration in groundwater, and chemical analysis methods are used to monitor the changes in reagent concentration and system operating parameters. According to the monitoring results, parameters such as reagent dosage and aeration intensity are adjusted in a timely manner to achieve the best purification effect. For example, if it is found that the VOCs concentration in a certain area decreases slowly, the reagent dosage can be appropriately increased or the aeration temperature can be increased. The amount of high-pressure steam or high-temperature air connected is controlled by adjusting the flow regulating valve on the pneumatic pump access pipe 5 to maintain the aeration temperature at 40°C. When high-pressure steam is connected, the steam pressure is 0.3MPa, and when high-temperature air is connected, the air temperature is 150°C.

[0041] The sealing performance of the pneumatic pump is checked every six months, the blockage of filter 202 is checked monthly, and the adsorption efficiency of the activated carbon adsorption tank is tested every two months. After the system has been running for a period of time, all components of the device are thoroughly inspected. Worn or failed components are promptly replaced based on the inspection results to ensure the long-term stable operation of the system and achieve effective groundwater purification. Throughout the process, the surrounding environment is closely monitored for any abnormal changes, such as soil color and odor, to ensure that the system is operating in an environmentally friendly manner and does not cause secondary pollution. Furthermore, long-term follow-up monitoring of the treated groundwater is conducted to evaluate the durability of the remediation effect.

[0042] This embodiment achieves efficient synergy between aeration and chemical treatment through precise control of chemical addition and diversified addition modes. The combined application of multiple chemicals and treatment technologies enhances the ability to treat complex pollution and adapts to a wider range of groundwater pollution scenarios. Strict system monitoring and maintenance measures ensure the long-term stable operation of the system. While effectively purifying groundwater, it is environmentally friendly and has a long-lasting remediation effect, providing a flexible, efficient and sustainable solution for groundwater remediation.

[0043] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any aspect, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the same elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. An in-situ purification integrated device for VOCs in groundwater, characterized in that The device includes an in-situ air stripping-aeration-agent dosing integrated pneumatic pump (1), a groundwater extraction well (2), an agent dosing pipe (3), a ground agent dosing device (4), a pneumatic pump access pipe (5), a ground tail gas treatment device (6), a blower (7), and a vapor extraction device (8). The in-situ air stripping-aeration-agent dosing integrated pneumatic pump (1) is gas-driven, and its air inlet end is connected to the blower (7) through a pipeline. The blower (7) is connected to the ground tail gas treatment device (6) through a pipeline and is used to receive the treated tail gas as a power source. One end of the agent dosing pipe (3) is connected to the ground agent dosing device (4), and the other end of the agent dosing pipe (3) is communicated with the in-situ air stripping-aeration-agent dosing integrated pneumatic pump (1). The agent dosing rate is controlled by the opening and closing size of the solenoid valve in the ground agent dosing device (4), and the control signal of the solenoid valve is generated and transmitted by a computer program. The pneumatic pump access pipe (5) is connected to the in-situ air stripping-aeration-agent dosing integrated pneumatic pump (1), and the pneumatic pump access pipe (5) is connected to a high-temperature air source, and a flow regulating valve is provided on the pneumatic pump access pipe (5). The ground tail gas treatment device (6) is connected to each extraction well pipe through a pipeline. An activated carbon adsorption tank is provided inside, and columnar activated carbon with a particle size of 3-5 mm is filled in the activated carbon adsorption tank. The gas treated by it can be pressurized and heated by the blower (7) and then pumped back into the in-situ air stripping-aeration-agent dosing integrated pneumatic pump (1).

2. The in-situ purification integrated device for VOCs in groundwater according to claim 1, characterized in that, An air access end (101) is provided at the bottom end of the in-situ air stripping-aeration-agent dosing integrated pneumatic pump (1). Inside the in-situ air stripping-aeration-agent dosing integrated pneumatic pump (1), a negative pressure suction section (102), a throat pipe gradual change section (103), and a high-pressure jet mixing section (104) are sequentially arranged from bottom to top. A liquid phase suction port (105) is provided on the outer surface of the in-situ air stripping-aeration-agent dosing integrated pneumatic pump (1), and the liquid phase suction port (105) is communicated with the negative pressure suction section (102). A pipeline connector one (106) is installed at the left end of the in-situ air stripping-aeration-agent dosing integrated pneumatic pump (1), and the pipeline connector one (106) is connected to the agent dosing pipe (3). A pipeline connector two (107) is installed at the bottom end of the air access end (101), and the pipeline connector two (107) is connected to the pneumatic pump access pipe (5). A check valve is provided inside the pipeline connector one (106). The check valve allows the agent to flow in one direction into the mixing chamber and is used to prevent the gas-liquid mixture in the mixing chamber from flowing back to the agent dosing pipe (3).

3. The in-situ purification integrated device for VOCs in groundwater according to claim 1, wherein, The groundwater extraction well (2) is a specially made double-layer stainless steel well pipe. The inner layer is a 304 stainless steel slotted pipe with spiral slits and a slit width of 0.1 - 0.5 mm. The outer layer is a stainless steel wire mesh structure. Gravel and quartz sand with a particle size of 2 - 3 mm are filled between the two layers. A middle barrier (201) is provided at the middle position of the groundwater extraction well (2), dividing the well pipe into upper and lower parts. The middle barrier (201) is made of rubber and fits tightly with the inner wall of the well pipe. The integrated pneumatic pump is installed in the lower layer of the well pipe. A filter screen (202) is provided in the upper layer of the groundwater extraction well (2). The filter screen (202) is made of stainless steel and has a mesh aperture of 0.1 - 0.5 mm. The filter screen (202) is connected to the vapor extraction device (8) through a pipeline.

4. The in-situ purification integrated device for VOCs in groundwater according to claim 3, wherein, The thickness of the middle barrier (201) is 5 - 10 cm. Annular sealing grooves are respectively provided on its upper and lower surfaces, and sealing rings are installed in the sealing grooves. The thickness of the filter screen (202) is 10 - 15 cm. The filter screen (202) is formed by stacking multiple layers of stainless steel wire meshes. The mesh aperture of each layer of wire mesh gradually decreases from the inside of the well pipe to the outside.

5. The in-situ purification integrated device for VOCs in groundwater according to claim 1, characterized in that, An anti-corrosion protection layer is provided on the outside of the groundwater extraction well (2). The anti-corrosion protection layer is an epoxy resin coating with a thickness of 0.5 - 1.5 mm.

6. Application method of in-situ purification integrated device for VOCs in groundwater, characterized in that, This method includes the following steps: Start the fan (7) and the vapor extraction device (8), extract the volatile polluted gas in the groundwater to the ground tail gas treatment device (6). The treated tail gas is pressurized and heated by the fan (7) and then transported to the in-situ air stripping - aeration - chemical agent dosing integrated pneumatic pump (1) as a power source. At the same time, the automatic pressure compensation device of the extraction pipeline of the fan (7) extracts ambient air when starting, and automatically closes after the air volume is balanced. Start the tail gas internal circulation. During the stage of extracting ambient air, the rotation speed of the fan (7) is 1000 - 1500 rpm. When switching to the tail gas internal circulation, the rotation speed of the fan (7) is adjusted to 800 - 1200 rpm; High-pressure gas enters the pneumatic pump to generate negative pressure, extracts the groundwater in the lower layer of the groundwater extraction well (2) to the upper layer through the air stripping extraction pipe. The groundwater is mixed with the gas at high speed in the pump body and then sprayed out at high speed by the nozzle to achieve in-well aeration. At the same time, the filter screen (202) in the upper layer of the well pipe intercepts water vapor. After the pollutants volatilize, they are taken away by the extraction device and enter the tail gas treatment device for cyclic treatment. The water circulates under gravity and slightly positive pressure. During the in-well aeration process, by adjusting the gas flow rate of the pneumatic pump, the upward flow velocity of the water in the well is 1 - 3 m / s. When performing in-well aeration, the access amount of high-temperature air is controlled by adjusting the flow regulating valve on the access pipe (5) of the pneumatic pump to keep the aeration temperature at 30 - 50 °C, and the access temperature of the high-temperature air is 100 - 200 °C. During the circulation process of the groundwater, every time after aeration and cyclic treatment, the residence time in the aquifer is 2 - 5 hours. And after each cyclic treatment, the concentration of VOCs in the groundwater is detected. When the concentration is reduced below the set threshold value, the purification treatment of this area is stopped; According to the repair requirements, prepare the repair agent in the ground agent dosing device (4), adjust the agent dosing rate by controlling the opening and closing size of the solenoid valve. The agent dosing can be carried out synchronously with aeration, that is, the agent is injected into the pneumatic pump under the action of negative pressure through the dosing pipe, mixed with groundwater and air and then sprayed out, and infiltrated back into the original formation under the action of hydraulic and air pressure to achieve agent dosing and mixing. When carried out synchronously, the ratio of the agent flow rate in the agent dosing pipe (3) to the gas flow rate in the pneumatic pump is 1:5 - 1:

10. It can also be carried out separately, that is, close the valve between the tail gas device and the pneumatic pump, and the fan (7) extracts ambient air and injects it into the well to pump the groundwater and the agent to the upper screen pipe section and then quickly discharges them under pressure to accelerate the agent dosing. When carried out separately, the flow rate of the ambient air extracted by the fan (7) is 1.2 - 1.5 times the gas flow rate during normal tail gas circulation.

7. The application method of the in-situ purification integrated device for VOCs in groundwater according to claim 6, characterized in that, During the separate dosing process of the agent, when the agent is an oxidation agent, the agent should complete at least 1 - 2 cycles in the lithological formation around the injection well to ensure uniform and sufficient agent dosing. When the agent is a reduction agent, add an appropriate amount of acid regulator to the groundwater extraction well (2) before dosing to adjust the pH value of the groundwater to 3 - 5 to improve the reduction reaction efficiency. During the whole application process, regularly regenerate the activated carbon adsorption tank in the ground tail gas treatment device (6). The regeneration period is 1 - 3 months, and the regeneration method is hot air purging. The temperature of the hot air is 120 - 150 °C, and the purging time is 2 - 4 hours.

8. The application method of the in-situ purification integrated device for VOCs in groundwater according to claim 6, characterized in that, Before starting the device, pretreat the formation around the groundwater extraction well (2), including injecting a cleaning agent. The cleaning agent is a surfactant solution with a concentration of 0.5% - 2%. During the application process, monitor the change of the groundwater level in real time, and adjust the operating parameters of the fan (7) and the pneumatic pump according to the water level change. During the agent dosing process, select appropriate agent types and dosing sequences according to the water quality and pollutant components of the groundwater. When there are multiple VOCs pollutants in the water, first dose the specific agent for the main pollutant, and then dose the auxiliary agent.

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