Permeable aerobic biological reaction wall based on piezoelectric effect enhancement

Abstract

The invention relates to a permeable aerobic biological reaction wall based on piezoelectric effect enhancement, which is characterized in that a piezoelectric material is used as a filler to be filled into a permeable biological reaction wall body, and pulse hydraulic pressure generated by flow field potential energy formed by underground water extraction is utilized to enable the surface of the piezoelectric material to deform to generate charges to form a local potential field to stimulate microbial activity; therefore, the microbial colonization and pollutant degradation capabilities are improved. Meanwhile, a partition plate of a hollow fiber membrane assembly is arranged in the permeable biological reaction wall, the in-situ aerobic metabolism efficiency of microorganisms is improved through ultra-micro bubble aeration, and the situation that volatile and semi-volatile organic pollutants in underground water are released and dissipated to influence the surrounding environment is avoided. According to the method, long-term efficient green low-carbon sustainable biological process control of the underground water composite organic pollutants is realized, the remediation efficiency of the underground water composite organic pollutants is remarkably improved, secondary pollution and remediation trailing rebound phenomena are avoided, and long-term underground water pollution risk management and control are realized.

Description

Technical Field

[0001] The invention relates to the technical field of groundwater pollution remediation, and in particular to a permeable aerobic biological reaction wall of piezoelectric materials and array hollow fiber membranes. Background Art

[0002] Groundwater extraction and treatment technology can quickly reduce the degree of groundwater pollution by extracting and treating contaminated groundwater through the establishment of a well group system, which can effectively control the flow of underground contaminated groundwater. The extracted contaminated groundwater can quickly reduce the concentration of pollutants through physical and chemical methods, but it is affected by the non-uniformity of groundwater flow speed, flow direction and permeability coefficient, resulting in tailing and rebound phenomena at the site after the extraction and treatment of contaminated groundwater, making it difficult to completely purify the contaminated site, resulting in low efficiency and high cost in the later stage.

[0003] Microbial remediation is a green and sustainable method that uses the natural metabolic process of microorganisms to degrade or transform pollutants without generating secondary pollution and causing little disturbance to the environment. Microorganisms under aerobic conditions have a fast metabolic rate and can degrade organic matter more quickly, shortening the remediation time. Aerobic microorganisms can completely mineralize organic pollutants into harmless carbon dioxide and water, providing more thorough pollutant removal. Although aerobic remediation requires aeration and oxygen supply, its energy consumption is usually lower than that of anaerobic remediation, and it does not produce odors and potential air pollution problems associated with anaerobic organisms. Complex organic polluted groundwater is often accompanied by heavy metal pollution, and the presence of heavy metal ions further affects microbial growth and degradation of pollutants. The anoxic groundwater environment inhibits the growth and metabolism of complex organic aerobic degrading bacteria. The aeration device with hollow fiber membrane as the core component can provide remediation gas in the form of ultrafine bubbles while avoiding the escape of volatile organic matter. Traditional bundle devices are prone to form biofilms, causing blockage and difficult to clean, and are not suitable for long-term operation.

[0004] Permeable reactive barrier (PRB) is a method for in-situ remediation of groundwater. It installs a wall filled with a specific reactive medium on the path of contaminated groundwater, so that pollutants in the groundwater react physically and chemically with the reactive medium when passing through the wall, thereby being removed or converted into an environmentally acceptable form. However, PRB technology is not suitable for sites with complex pollution types, because the pollution removal object of PRB is determined by the reactive medium it is filled with. At the same time, over time, the reactive medium may decrease the effectiveness of the PRB system reaction due to the accumulation of pollutants and the coverage of sediments, which may require regular replacement or regeneration of the reactive medium, increasing maintenance costs and complexity.

[0005] Therefore, developing a permeable reaction wall for continuous deep purification of low-concentration composite organic-contaminated groundwater is a technical solution that urgently needs to be solved. Summary of the invention

[0006] The purpose of the present invention is to solve the above-mentioned defects of the prior art and provide a permeable aerobic bioreaction wall (Piezoelectric permeable reactive aerobicbiobarrier, PPRABB) based on piezoelectric effect enhancement.

[0007] In order to achieve the above-mentioned purpose, the scheme of the present invention is as follows: a permeable aerobic biological reaction wall strengthened based on piezoelectric effect, the reaction wall comprises a piezoelectric material module, an array hollow fiber module, an extraction pump, an air pump, a rotor flowmeter, a hydraulic electric control valve and a water flow meter, wherein the piezoelectric material module and the array hollow fiber membrane module are staggered to form the main body of the permeable biological reaction wall, and the piezoelectric material module is close to the soil at both ends.

[0008] The air pump is connected to the air inlet of the hollow fiber membrane module through a gas transport pipeline. The rotor flowmeter is arranged on the gas transport pipeline. The gas is evenly transported to each hollow fiber membrane fiber through the air pipeline arranged on the hollow fiber membrane module frame. At the same time, the hollow fiber membrane module frame fixes and arranges the hollow fiber membrane mousse.

[0009] The extraction pump is located upstream of the entire reaction wall and is connected to the groundwater source through a pipeline. The extraction pump draws water through the pipeline without directly contacting the groundwater, ensuring effective extraction and transportation of water. The hydraulic electric control valve is installed on the outlet pipe of the extraction pump, immediately after the extraction pump. The hydraulic electric control valve is used to adjust the pressure and flow of the water flow to ensure that the system can dynamically adjust the extraction effect according to demand. The water flow meter is set in the pipeline section downstream of the hydraulic electric control valve, at a certain distance from the control valve to avoid interference. The water flow meter monitors the water flow rate through the pipeline in real time and provides the necessary data to optimize the operation of the system.

[0010] Preferably, the piezoelectric material and the stainless steel orifice plate form a piezoelectric material module, and the stainless steel orifice plate provides support and positioning on both sides of the piezoelectric material to prevent the piezoelectric material from migrating and being unable to bear force accurately. The perforated plate body is made of stainless steel, and the internal pores allow water to flow out with almost no resistance. The hole size and hole density are adjusted according to actual needs.

[0011] The piezoelectric material is a composite piezoelectric material, which is composed of lead-free ceramic particles (potassium sodium niobate KNN and barium titanate BT) and piezoelectric polymer (polyvinylidene fluoride PVDF).

[0012] The composite piezoelectric material adds KNN and BT particles to PVDF slurry, and adopts the additive manufacturing technology of "layered manufacturing, layer by layer manufacturing" to prepare the composite piezoelectric material. The mass ratio of KNN, BT, and PVDF is 0.1-0.5: 0.1-0.5: 1-3. The piezoelectric material can block soil particles from entering the permeable aerobic biological reaction wall while being water-permeable, and uses the hydraulic pressure in the process of groundwater migration to generate an uneven electric field to reduce the heavy metal ions in the composite organic polluted groundwater. At the same time, it can stimulate the degradation activity of microorganisms under low temperature conditions; the piezoelectric material can be replaced with a new piezoelectric material with better biocompatibility, stronger power generation performance, better stability, and higher water permeability; the piezoelectric material can be replaced with a new piezoelectric material with better biocompatibility, stronger power generation performance, better stability, and higher water permeability. The piezoelectric material has the potential to resist pollution and blockage against organic matter, oils, and proteins, thereby improving the durability of the piezoelectric material.

[0013] Preferably, the array hollow fiber membrane module is composed of a plurality of hollow fiber membranes tightly arranged in an array, each array hollow fiber membrane has a uniform thickness and is positioned with a card slot. The wall can withstand pulse hydraulic pressure without displacement, and avoid hydraulic pressure causing the wall to move, resulting in groundwater not completely penetrating the permeable biological reaction wall; the hollow fiber membrane module provides dissolved oxygen in the form of ultra-microbubbles while avoiding the escape of volatile organic compounds. The gas transport pipeline can be used not only to provide gas, but also to transport liquid supplies. For example, pH regulating liquid, exogenous functional microorganisms, and liquid nutrients.

[0014] Preferably, the bottom and surrounding of the permeable bioreactor wall are provided with preset slots for positioning the piezoelectric material and the array hollow fiber membrane.

[0015] Tightly fitting transversely arranged hollow fiber membrane filaments are fixed on an array hollow fiber membrane frame to form an array hollow fiber membrane. Several array hollow fiber membranes form a hollow fiber membrane module, which is fitted with a piezoelectric material module to form a unit. PM-PRBB is composed of several of the above units.

[0016] The spacing between hollow fiber membranes is 0.1-0.3cm, the pore size is 0.05-0.1μm, the inner diameter is 0.5-1mm, the outer diameter is 1-2mm, the length is 0.5-5m, and the aeration volume is 0.1-0.5L / m 2 ·min.

[0017] Preferably, the bottom of the permeable bioreactor wall should be connected to the upper layer of the first weakly permeable layer. At the same time, cement is sprayed and cut into the soil at a certain pressure on both sides of the reaction wall through high-pressure jet grouting, and mixed with the soil to form a cylindrical pile body, thereby forming a water-stop curtain, thereby promoting the contaminated groundwater to flow completely through the permeable bioreactor wall based on piezoelectric materials.

[0018] Preferably, the extraction pump pressure is within the range of 1-10MPa, and the groundwater extraction flow rate is controlled by adjusting the pressure, with a high liquid flow rate of 5-10m / s and a low liquid flow rate of 0.1-0.5m / s; the groundwater is extracted from the soil layer at a specified depth by using the extraction pump, and the periodic regulation control valve controls the extraction flow rate, thereby transmitting pulse hydraulic pressure to the piezoelectric material, pre-buried gas transport pipelines, and the pipelines are connected to the air inlet of the array hollow fiber membrane module, and the connection is wrapped with polyurethane material to improve air tightness and durability. The piezoelectric material modules and the array hollow fiber membrane modules are staggered to form the main structure of the permeable bioreactor wall, so that the piezoelectric material modules are close to the soil at both ends, and the middle part of the permeable bioreactor wall can be adjusted in quantity and order according to the site hydrogeological conditions, site scale and pollutant removal effect.

[0019] Preferably, the surface of the arrayed hollow fiber membranes is arranged to have a sinusoidal corrugated structure.

[0020] The PPRABB provided by the present invention, the control system includes an extraction system for controlling the flow of contaminated groundwater, and the pulse hydraulic pressure generated by the flow field potential energy formed by extracting the contaminated groundwater causes the surface of the piezoelectric material to deform, thereby generating electric charges and forming a local electrochemical area.

[0021] Furthermore, the electric field can induce the electromigration of charged molecules (including electron donors / acceptors, soluble pollutants and nutrients), inducing pore water flow through electroosmosis and improving its bioavailability in underground aquifers.

[0022] Furthermore, electrochemical reduction can be applied to most heavy metals, such as copper, chromium, cadmium, mercury, uranium and vanadium. Electroactive bacteria (such as Geobacter) are widely present in groundwater environments and can effectively catalyze metal reduction. Avoid metal stress in groundwater organic pollution degradation functional microbial activity.

[0023] Furthermore, electrochemical reactions under low-temperature conditions underground can stimulate the activity of microorganisms and enhance their ability to metabolize complex organic pollutants.

[0024] Furthermore, the electric field attracts the migration of some electroactive functional microorganisms, alleviating the pore blockage caused by excessive growth of microorganisms on the array hollow fiber membrane.

[0025] Furthermore, the piezoelectric material has the potential to resist pollution and clogging against organic matter, oils and proteins, thus improving the durability of the piezoelectric material.

[0026] Specifically, the piezoelectric material is a composite piezoelectric material composed of lead-free ceramic particles (potassium sodium niobate KNN and barium titanate BT) and a piezoelectric polymer (polyvinylidene fluoride PVDF).

[0027] Preferably, the composite piezoelectric material is prepared by adding KNN and BT particles into PVDF slurry and adopting the additive manufacturing technology of "layer-by-layer manufacturing".

[0028] Specifically, the perforated plate body is used to provide support and positioning on both sides of the piezoelectric material to form a piezoelectric material module, thereby preventing the piezoelectric material from being moved and unable to be accurately stressed. The perforated plate body is made of stainless steel, and the internal pores allow water to flow out with almost no resistance. The hole size and hole density are adjusted according to actual needs.

[0029] Furthermore, ultrafine bubble aeration is achieved through array hollow fiber membranes. The tight sinusoidal corrugated structure on the surface of the array hollow fiber membranes is not easy to be blocked, has strong anti-pollution ability, increases the water impact load of the device and enhances the stability of the system.

[0030] Furthermore, the array hollow fiber membrane is connected to an air pump to obtain external oxygen. The ultra-high surface energy of ultra-fine bubbles (less than 2μm in diameter) can be tightly combined with water molecules, allowing the bubbles to settle and dissipate in the water. The microporous structure of the hollow fiber membrane is equipped with a gas control workstation, which allows the blown air to enter the groundwater in the form of ultra-fine bubbles, increasing the dissolved oxygen in the water while preventing the escape of volatile organic compounds in the groundwater.

[0031] Furthermore, aeration is used to provide oxygen required for aerobic functional microorganisms to degrade complex organic pollutants, activate indigenous functional bacteria, and establish an effective functional microbial community.

[0032] Furthermore, PPRABB can adapt to different hydrogeological conditions and pollutant characteristics, and has a certain degree of flexibility. Some microorganisms can degrade some refractory organic pollutants that are difficult to treat with physical and chemical methods. Microbial remediation can not only remove pollutants, but also promote the health and stability of soil and groundwater ecosystems, and help restore and maintain ecological balance.

[0033] Specifically, an array of hollow fiber membranes is formed by tightly fitting and laterally arranged hollow fiber membrane filaments, and several array hollow fiber membranes form a hollow fiber membrane module, which is fitted with a piezoelectric material module to form a unit. PM-PRBB is composed of several of the above units.

[0034] Preferably, the spacing between the hollow fiber membrane fibers is 0.1-0.3 cm, the membrane fiber pore size is 0.05-0.1 μm, the membrane fiber inner diameter is 0.5-1 mm, the membrane fiber outer diameter is 1-2 mm, the membrane fiber length is 0.5-5 m, and the aeration volume is 0.1-0.5 L / m 2 ·min.

[0035] At the same time, the present invention also provides a control method for the permeable bioreaction wall technology based on piezoelectric materials, comprising the following steps:

[0036] (1) According to the target pollution plume of the site, the PPRABB is placed downstream of the groundwater flow direction. The wall height range covers the pollution plume area, and the wall width is determined to be 2-5m according to the size of the site.

[0037] (2) The depth of the PPRABB should reach the silty clay layer or the first weak permeable layer. The surrounding area should be equipped with vertical barriers of the same width to guide the contaminated groundwater through the wall. The high-pressure jet grouting method is used to spray cement at a certain pressure to cut the soil, mix it with the soil to form a cylindrical pile body, and form a water-stop curtain.

[0038] (3) Construct a groundwater extraction system to extract groundwater behind the PPRABB along the groundwater flow direction, including water distribution observation ports, extraction diversion pipes, pebble layers, extraction wells, etc. Equip a monitoring and control system, including hydraulic electric control valves, water flow meters, etc. The hydraulic electric control valves and water flow meters are controlled during the extraction process to form periodic pulse water pressure.

[0039] The beneficial effects of the present invention are:

[0040] 1. Without an external power supply, the permeable bioreactor wall based on piezoelectric materials uses the pulse hydraulic pressure generated by the flow field potential energy formed by groundwater extraction to deform the surface of the piezoelectric material to generate charges and form a local electric potential field, thereby alleviating the wall blockage phenomenon, improving the wall durability, reducing the inhibition of heavy metal ions on the activity of microorganisms, increasing the bioavailability of electron donors / acceptors, nutrients and pollutants, and promoting microbial degradation activity through electrical stimulation.

[0041] 2. The array hollow fiber membrane is aerated in an ultra-fine bubble manner, providing oxygen required by aerobic microorganisms while avoiding the escape of volatile or semi-volatile organic matter. During operation, the membrane surface presents a sinusoidal corrugated structure, which can slow down the pore blockage phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of a permeable bioreaction wall structure based on piezoelectric materials and a site application of the present invention;

[0043] Figure 2 A three-dimensional diagram of an array of hollow fiber membranes of the present invention;

[0044] Figure 3 It is a schematic diagram of the stainless steel orifice plate of the present invention.

[0045] In the figure: 1. piezoelectric material; 2. array hollow fiber membrane; 3. stainless steel orifice plate; 4. extraction pump; 5. air pump; 6. rotor flow meter; 7. hydraulic electric control valve; 8. water flow meter; 9. slot; 10. hollow fiber membrane filament; 11. array hollow fiber membrane frame; 12. air inlet of array hollow fiber membrane frame. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0047] Example 1: See Figure 1-Figure 3 , a permeable aerobic biological reaction wall based on piezoelectric effect enhancement, the reaction wall includes a piezoelectric material module, an array hollow fiber module, an extraction pump 4, an air pump 5, a rotor flowmeter 6, a hydraulic electric control valve 7 and a water flow meter 8, wherein the piezoelectric material module and the array hollow fiber membrane module are staggered to form the main body of the permeable biological reaction wall, the piezoelectric material module is close to the soil at both ends, the air pump 5 is connected to the air inlet of the hollow fiber membrane module through a gas transport pipeline, the rotor flowmeter 6 is arranged on the gas transport pipeline, and the gas is evenly transported to each hollow fiber membrane fiber through the gas pipeline arranged on the hollow fiber membrane module frame, and the hollow fiber membrane module frame plays a role in fixing and arranging the hollow fiber membrane mousse. The extraction pump 4 is located at the upstream position of the entire reaction wall, connected to the groundwater source through a pipeline, and the extraction pump 4 sucks water through the pipeline without directly contacting the groundwater, ensuring the effective extraction and transportation of water. The hydraulic electric control valve 7 is installed on the outlet pipe of the extraction pump, immediately after the extraction pump. The hydraulic electric control valve 7 is used to adjust the pressure and flow of the water flow to ensure that the system can dynamically adjust the extraction effect according to demand. The water flow meter 8 is set in the pipeline section downstream of the hydraulic electric control valve, at a certain distance from the control valve to avoid interference. The water flow meter 8 monitors the water flow rate through the pipeline in real time and provides necessary data to optimize the operation of the system.

[0048] Preferably, the piezoelectric material 1 and the stainless steel orifice plate 3 form a piezoelectric material module, and the stainless steel orifice plate 3 provides support and positioning on both sides of the piezoelectric material to avoid the piezoelectric material from migrating and being unable to be accurately stressed. The perforated plate body is made of stainless steel, and the internal pores allow water to flow out with almost no resistance. The hole size and hole density are adjusted according to actual needs.

[0049] The piezoelectric material 1 is a composite piezoelectric material, which is composed of lead-free ceramic particles (potassium sodium niobate KNN and barium titanate BT) and piezoelectric polymer (polyvinylidene fluoride PVDF).

[0050] The composite piezoelectric material adds KNN and BT particles to PVDF slurry, and adopts the additive manufacturing technology of "layered manufacturing, layer by layer manufacturing" to prepare the composite piezoelectric material. The mass ratio of KNN, BT, and PVDF is 0.1-0.5: 0.1-0.5: 1-3. The piezoelectric material can block soil particles from entering the permeable aerobic biological reaction wall while being water-permeable, and uses the hydraulic pressure in the process of groundwater migration to generate an uneven electric field to reduce the heavy metal ions in the composite organic polluted groundwater. At the same time, it can stimulate the degradation activity of microorganisms under low temperature conditions; the piezoelectric material can be replaced with a new piezoelectric material with better biocompatibility, stronger power generation performance, better stability, and higher water permeability; the piezoelectric material can be replaced with a new piezoelectric material with better biocompatibility, stronger power generation performance, better stability, and higher water permeability. The piezoelectric material has the potential to resist pollution and blockage against organic matter, oils, and proteins, thereby improving the durability of the piezoelectric material.

[0051] Preferably, the array hollow fiber membrane module is composed of a plurality of hollow fiber membranes tightly arranged in an array, each array hollow fiber membrane has a uniform thickness and is positioned with a card slot. The wall can withstand pulse hydraulic pressure without displacement, and avoid hydraulic pressure causing the wall to move, resulting in groundwater not completely penetrating the permeable biological reaction wall; the hollow fiber membrane module provides dissolved oxygen in the form of ultra-microbubbles while avoiding the escape of volatile organic compounds. The gas transport pipeline can be used not only to provide gas, but also to transport liquid supplies. For example, pH regulating liquid, exogenous functional microorganisms, and liquid nutrients.

[0052] The bottom and surrounding of the permeable bioreactor wall are provided with preset slots 9 for positioning the piezoelectric material and the array hollow fiber membrane.

[0053] Tightly fitting and laterally arranged hollow fiber membrane filaments 10 are fixed on an array hollow fiber membrane frame 11 to form an array hollow fiber membrane 2. Several array hollow fiber membranes 2 form a hollow fiber membrane module, which is fitted with a piezoelectric material module to form a unit. PM-PRBB is composed of several of the above-mentioned units.

[0054] The spacing between hollow fiber membranes is 0.1-0.3cm, the pore size is 0.05-0.1μm, the inner diameter is 0.5-1mm, the outer diameter is 1-2mm, the length is 0.5-5m, and the aeration volume is 0.1-0.5L / m 2 ·min.

[0055] The bottom of the permeable biological reaction wall should be connected to the upper layer of the first weakly permeable layer. At the same time, cement is sprayed and cut into the soil at a certain pressure on both sides of the reaction wall through high-pressure jet grouting method, and mixed with the soil to form a cylindrical pile body, thereby forming a water-stop curtain, which promotes the contaminated groundwater to flow completely through the permeable biological reaction wall based on piezoelectric materials.

[0056] The extraction pump pressure is in the range of 1-10MPa. The groundwater extraction flow rate is controlled by adjusting the pressure. The high liquid flow rate is 5-10m / s and the low liquid flow rate is 0.1-0.5m / s. The extraction pump is used to extract groundwater from the soil layer at a specified depth. The periodic regulation control valve will control the extraction flow rate, thereby transmitting pulse hydraulic pressure to the piezoelectric material. The gas transportation pipeline is pre-buried, and the pipeline is connected to the air inlet of the array hollow fiber membrane module. The connection is wrapped with polyurethane material to improve air tightness and durability. The piezoelectric material module and the array hollow fiber membrane module are staggered to form the main structure of the permeable biological reaction wall, so that the piezoelectric material module is close to the soil at both ends. The middle part of the permeable biological reaction wall can be adjusted in quantity and order according to the site hydrogeological conditions, site scale and pollutant removal effect. The surface of the array hollow fiber membrane is set to a sine corrugated structure.

[0057] Example 2

[0058] A groundwater composite organic pollution site (500m×1000m) was built at the decommissioned site of a pesticide production plant. A permeable biological reaction wall device with a length of 400m, a width of 2m, and a depth of 10m was installed at the lowered position of the groundwater flow line of the site. An extraction well with a depth of 6m was built upstream of the pollution plume. The air pump and the array hollow fiber membrane module are connected through a gas transport pipeline. The air pump is equipped with a solar power supply system, which does not require external current and can achieve long-term ultra-fine bubble aeration.

[0059] Open the hydraulic electric control valve 7, run the extraction pump 4 to start extracting the composite organic contaminated groundwater at a depth of 6m, and control the groundwater flow rate to 0.2m / s by observing the water flow rate meter 8, and continue to inlet water for more than 30min to ensure that the soil in the soil sample room is saturated with water. Then, under the control of the water flow rate meter 8, the groundwater flow rate is switched between 0.2m / s and 5m / s, and the switching cycle is 10min to achieve a periodic pulse groundwater flow field. Sample the groundwater flowing through the reaction wall every cycle to monitor water quality indicators and pollutant concentrations.

[0060] The dissolved oxygen in contaminated groundwater is usually lower than 1 mg / L, which is relatively hypoxic. Turn on the air pump 5 to pump air into the array hollow fiber membrane 2 device to replenish the dissolved oxygen concentration in the groundwater in the form of ultrafine bubbles, so that the dissolved oxygen concentration in the biological function chamber is maintained at 4 to 6 mg / L, providing sufficient oxygen for aerobic microorganisms.

[0061] After 90 days of using the permeable biological reaction wall device of the present invention to remove composite organic pollution in groundwater in a contaminated groundwater control area of ​​a chemical decommissioning site, the composite organic concentration decreased from the initial 2.4±2.54 mg / L to 0.03±0.01 mg / L, indicating that the present invention enhances the bioremediation effect of composite organic pollution in groundwater.

[0062] Example 3

[0063] During the long-term operation of a fine chemical plant, the groundwater was seriously polluted due to improper wastewater management. The pollutants mainly include a variety of heavy metal ions and organic pollutants. The groundwater pollution is wide and the concentration of pollutants is high, posing a potential threat to the surrounding environment and residents' health. Therefore, a permeable aerobic biological reaction wall (PRB) based on piezoelectric effect enhancement, which integrates physical, chemical and biological remediation technologies, was selected to treat the polluted site. The distribution range and concentration of pollutants were determined through drilling and water quality monitoring. The main flow direction of groundwater was determined based on hydrogeological surveys. The design length is 100m, the thickness is 1m, and the depth is 8m to ensure that the entire contaminated layer is covered. The piezoelectric material is mixed into the filling material in the ratio of KNN: BT: PVDF = 0.2: 0.2: 2. Gravel, ceramsite and activated carbon are mixed to ensure sufficient permeability and adsorption capacity. Iron filings are used to promote the reduction reaction of heavy metals. A trench with a width of 2m and a depth of 8m is excavated along the groundwater flow to ensure that the trench is stable and avoid collapse. An extraction well and an extraction pump 4 are installed downstream of the reaction wall, with a well spacing of 30m, to ensure that the velocity of groundwater extraction can be periodically regulated, thereby controlling the velocity of groundwater flowing through the reaction wall. The composite organic polluted groundwater contains metal ions such as copper (2.12μg / L), zinc (5.03μg / L), aluminum (13.73μg / L), manganese (45.79μg / L), and lead (0.61μg / L), which are not conducive to the growth and metabolism of functional microorganisms. When groundwater flows through the reaction wall, due to the hydraulic action generated by the water flow, the piezoelectric material 1 deforms and generates a local electric field. The local electric field promotes the reduction reaction of heavy metal ions, generates insoluble precipitates, and is fixed in the reaction wall, reducing the concentration of heavy metals in the groundwater. While reducing heavy metal ions, it provides electron donors required by microorganisms and accelerates biodegradation. The total removal rate of metal ions in groundwater reaches 93.6%, and the total concentration of organic pollutants is reduced by more than 70%, meeting environmental safety standards.

[0064] The specific embodiments shown above provide a detailed description of the problems existing in the above-mentioned prior art solved by the present invention, the proposed solutions and the implementation effectiveness. The above are only specific embodiments of the present invention, and it should be understood that any modifications, equivalent substitutions and improvements made in accordance with the spirit of the invention should be included in the scope of protection of the present invention.

Claims

1. A permeable aerobic biological reaction wall based on piezoelectric effect enhancement, characterized in that: The reaction wall includes a piezoelectric material module, an array hollow fiber module, an extraction pump, an air pump, a rotor flow meter, a hydraulic electric control valve and a water flow meter. Among them, the piezoelectric material modules and the array hollow fiber membrane modules are arranged in a staggered manner to form the main body of the permeable biological reaction wall. The piezoelectric material modules are close to the soil at both ends. The air pump is connected to the air inlet of the hollow fiber membrane module through a gas transport pipeline, and a rotor flowmeter is arranged on the gas transport pipeline. The extraction pump is located upstream of the entire reaction wall and is connected to the groundwater source through a pipeline. The hydraulic electric control valve is installed on the outlet pipe of the extraction pump, and the water flow meter is set in the pipeline section downstream of the hydraulic electric control valve.

2. The permeable aerobic biological reaction wall based on piezoelectric effect enhancement according to claim 1 is characterized in that: The piezoelectric material and the stainless steel orifice plate form a piezoelectric material module, and the stainless steel orifice plate provides support and positioning on both sides of the piezoelectric material.

3. The permeable aerobic biological reaction wall based on piezoelectric effect enhancement according to claim 2 is characterized in that: The piezoelectric material is a composite piezoelectric material composed of lead-free ceramic particles and piezoelectric polymer. The composite piezoelectric material is prepared by adding KNN and BT particles into PVDF slurry and adopting the additive manufacturing technology of "layered manufacturing, layer by layer manufacturing". The mass ratio of KNN, BT and PVDF is 0.1-0.5:0.1-0.5:1-3.

4. The permeable aerobic biological reaction wall based on piezoelectric effect enhancement according to claim 1 is characterized in that: The array hollow fiber membrane module is composed of multiple hollow fiber membranes tightly arranged in an array. Each array hollow fiber membrane has a uniform thickness and is positioned with a slot.

5. The permeable aerobic biological reaction wall based on piezoelectric effect enhancement according to claim 1 is characterized in that: The bottom and surrounding of the permeable bioreactor wall are provided with preset slots for positioning piezoelectric materials and arrayed hollow fiber membranes.

6. The permeable aerobic biological reaction wall based on piezoelectric effect enhancement according to claim 1 is characterized in that: Tightly fitting transversely arranged hollow fiber membrane filaments are fixed on an array hollow fiber membrane frame to form an array hollow fiber membrane. Several array hollow fiber membranes form a hollow fiber membrane module, which is fitted with a piezoelectric material module to form a unit. PM-PRBB is composed of several of the above units.

7. The permeable aerobic biological reaction wall based on piezoelectric effect enhancement according to claim 1, characterized in that: The bottom of the permeable biological reaction wall should be connected to the upper layer of the first weakly permeable layer. At the same time, cement is sprayed and cut into the soil at a certain pressure on both sides of the reaction wall through high-pressure jet grouting method, and mixed with the soil to form a cylindrical pile body, thereby forming a water-stop curtain, which promotes the contaminated groundwater to flow completely through the permeable biological reaction wall based on piezoelectric materials.

8. The permeable aerobic biological reaction wall based on piezoelectric effect enhancement according to claim 1, characterized in that: The extraction pump pressure is in the range of 1-10MPa. The groundwater extraction flow rate is controlled by adjusting the pressure. The high liquid flow rate is 5-10m / s and the low liquid flow rate is 0.1-0.5m / s.

9. The permeable aerobic biological reaction wall based on piezoelectric effect enhancement according to claim 1, characterized in that: The surface of the array hollow fiber membrane is arranged as a sinusoidal corrugated structure.

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