An apparatus and method for groundwater remediation

Abstract

The application discloses a groundwater remediation device and method, and the device comprises multiple-stage funnel-door type permeable reaction walls arranged at intervals.

Description

TECHNICAL FIELD

[0001] The present application relates to a groundwater remediation device and method, belonging to the technical field of groundwater pollution remediation. BACKGROUND

[0002] Groundwater, as a component of water resources system, has important influence on water cycle and water supply. Heavy metals and organochlorinated hydrocarbons in groundwater are seriously polluted, which threatens human health and ecological safety, and hinders the sustainable green development of economy. Groundwater chlorinated hydrocarbon remediation methods are divided into in-situ remediation and ex-situ remediation, such as permeable reactive barrier technology and pump and treat technology. Permeable reactive barrier technology is to install a continuous wall filled with permeable reactive media in the groundwater aquifer to intercept the groundwater pollution plume. The wall is perpendicular to the groundwater flow direction. When the pollution plume passes through the wall under the action of natural hydraulic gradient, the pollutants in the wall are transformed into environmentally acceptable substances through precipitation, adsorption, oxidation-reduction, biodegradation and other effects, thereby reducing the concentration of groundwater pollutants and achieving the removal of pollutants.

[0003] Permeable reactive barrier (PRB) technology is a new technology for groundwater remediation, including continuous wall PRB and water-sealed funnel-water gate PRB. Continuous wall PRB is suitable for treating small groundwater pollution plume, and the wall can cover the width and depth of the pollutants. Water-sealed funnel-water gate PRB has a smaller length, is suitable for treating large-area polluted groundwater, and has the advantages of small environmental disturbance, stable treatment effect, low operation and maintenance cost, and broad application prospect.

[0004] The selection of permeable reactive barrier medium material is the key to the effect of groundwater remediation. The medium includes zero-valent iron, zeolite, clay, activated carbon and carbon source for enhancing microbial activity. Among them, zero-valent iron reduces the valence of heavy metals or degrades organic matter through reduction, thereby reducing the mobility or toxicity of pollutants; zeolite, clay, activated carbon and other materials remove pollutants through adsorption and precipitation; carbon source, nutrients or microbial carriers enhance microbial reaction activity to degrade organic pollutants.

[0005] The existing permeable reactive wall generally intercepts the contaminant plume by excavating a large area of the reactive wall trench, filling the trench with a whole active material wall that can permeate water, and removing or converting the pollutants in the material wall through precipitation, adsorption, oxidation-reduction, biodegradation, etc., to achieve the purpose of purifying groundwater. With the passage of time, the reaction material filled in the wall is gradually blocked by reaction products, the reaction capacity reaches saturation, the removal rate decreases, leading to system paralysis, and because the filling volume of the reaction material is large, the material is difficult to replace. The selection of active materials is determined according to the pollutants to be removed, and there are problems such as single pollutant treatment. In addition, chlorinated hydrocarbons are a complex class of organic pollutants, and single oxidation or reduction cannot completely remove the pollutants, leaving toxic by-products. So far, the existing permeable reactive wall technology cannot effectively solve these problems. SUMMARY

[0006] To solve the above problems, the present application provides a groundwater remediation device and method, based on the multi-stage synergistic effect of reduction-oxidation-microbial enhanced degradation, which can continuously in-situ remediate groundwater chlorinated hydrocarbon organic pollutants through three-stage permeable reactive walls, completely remove pollutants, and simultaneously treat multiple organic and inorganic pollutants, with the advantages of high efficiency, easy replacement of reaction materials, simple construction, and convenient maintenance. The technical solution adopted by the present application is as follows:

[0007] A groundwater remediation device, comprising a plurality of multi-stage funnel-gate permeable reactive walls arranged at intervals from the downstream to the downstream of the pollution plume, and each multi-stage funnel-gate permeable reactive wall comprises:

[0008] A permeable reactive wall is arranged vertically to the groundwater flow direction, comprising alternately connected reaction wells and impermeable walls, and a plurality of reaction units are placed in series in the reaction wells;

[0009] The reaction units in the first-stage funnel-gate permeable reactive wall are filled with mixed materials, and the mixed materials are composed of zero-valent iron, activated carbon and clay;

[0010] The reaction units in the second-stage funnel-gate permeable reactive wall are filled with slow-release materials, and the slow-release materials are composed of persulfate and citrate slow-release materials;

[0011] The reaction units in the third-stage funnel-gate permeable reactive wall are filled with functional materials, and the functional materials are composed of activated carbon, clay, microbial inoculum, carbon source, nitrogen source, phosphorus source, metal ions, and essential nutrients for microorganisms, including water, growth factors, and trace elements such as zinc, molybdenum, nickel, etc.;

[0012] A water barrier is connected at both ends of the permeable reactive wall.

[0013] Optionally, the distance between adjacent reaction wells is 1-3 m, the depth of the reaction well is greater than the depth of the groundwater pollution by 0.5 m, the reaction well comprises a pipe vertically arranged, pipe covers at the upper and lower ends of the pipe, and a reverse osmosis layer composed of quartz sand and gravel surrounding the pipe, the pipe wall is provided with a plurality of water inlet and outlet holes, the particle size of the quartz sand is 1-3 mm, the particle size of the gravel is 1-3 cm, the reverse osmosis layer is filled to a height of 0.5 m above the water inlet and outlet hole area of the pipe, and clay with a height greater than 0.5 m is further filled in the upper part of the reverse osmosis layer.

[0014] Optionally, the diameter of the pipe is 0.5-1.5 m, the material is HDPE or PVC, the depth of the impervious wall and the cutoff wall is consistent, and the impervious wall overlaps the outer wall of the pipe through the reverse osmosis layer, thereby separating the reaction well into a water inlet area on the upstream side and a water outlet area on the downstream side.

[0015] Optionally, the cutoff wall and the impervious wall use single-shaft or double-shaft mixing pile water stop curtain, the longitudinal depth penetrates the first layer of phreatic aquifer and reaches at least 0.5 m below the relative aquiclude; the cutoff wall is inclined to the upstream side of the permeable reaction wall, and the included angle with the permeable reaction wall is 110-160°, and the length of the cutoff wall at either end exceeds the pollution plume by 1-2 m.

[0016] Optionally, in the mixed material, the mass ratio of zero-valent iron, activated carbon and clay is 1:0.5-2:0.5-2;

[0017] In the slow-release material, the mass ratio of persulfate and citrate slow-release material is 1:1, and the pH range of the slow-release filler releasing the persulfate in the core is between 6.0 and 7.8;

[0018] In the functional material, the mass ratio of activated carbon and clay is 1:1, each kilogram of solid material contains 0-120 g / kg of carbon source, 0-12 g / kg of nitrogen source, 0-6 g / kg of phosphorus source, 0.15-2.0 g of MgSO4·7H2O, 0.15-2.0 g of KH2PO4, and 0.06-1.2 g of CaCl2; 0.8-5.5 ml / kg of essential nutrients for microorganisms, and microbial agents.

[0019] Optionally, the reaction unit is a round frame welded from a stainless steel solid pipe, the diameter of the reaction unit is 0.2-0.9 m, the length is 0.5-1 m, and the inside of the reaction unit is embedded with water-permeable geotextile; the ends of adjacent reaction units are connected by hooks, thereby connecting the adjacent reaction units into a reaction unit assembly, and the height of the reaction unit assembly reaches 0.5 m above the groundwater depth in the reaction well.

[0020] Optionally, a support frame is arranged on the outer periphery of the reaction unit of the third-stage reaction well for hanging biological biofilm fillers, and the biological biofilm fillers are soft or semi-soft fillers.

[0021] Optionally, an aeration pipe and a sample automatic detection and analysis device are arranged on the support frame, the aeration pipe is installed on the upstream side and the bottom of the reaction well, the aeration pipe is connected to an air compressor through a valve, and the sample automatic detection and analysis device is used for automatic collection, detection and analysis of multi-layer water quality samples.

[0022] Optionally, a plant planting belt is constructed between the permeable reaction walls of the secondary and tertiary funnel-door permeable reaction walls, perennial deep-rooted plants are planted in the plant planting belt, iron-tolerant ectomycorrhizae are inoculated around the plant root systems, the planting soil is pH-adjusted by using a magnesium peroxide alkaline oxide, the perennial deep-rooted plants are one or more of mulberry, sycamore, kapok, white wax, camphor tree, ailanthus, and pine, the planting density is 3x3-7x7 m 2 , and the addition amount of the iron-tolerant ectomycorrhizae is 0.1%-1%.

[0023] The application also provides a groundwater remediation method, and a remediation principle includes:

[0024] A plurality of levels of funnel-door permeable reaction walls are arranged downstream of the pollution plume, each level of funnel-door permeable reaction wall includes a permeable reaction wall and a waterproof wall connected to both ends of the permeable reaction wall, the permeable reaction wall is arranged perpendicular to the groundwater flow direction and includes alternately connected reaction wells and impervious walls, and a plurality of reaction units are arranged in series in the reaction wells;

[0025] Mixed materials are filled in the reaction units in the first level of funnel-door permeable reaction wall, the mixed materials are mixed from zero-valent iron, activated carbon and clay, slow-release materials are filled in the reaction units in the second level of funnel-door permeable reaction wall, the slow-release materials are composed of persulfate and citrate slow-release materials, and functional materials are filled in the reaction units in the third level of funnel-door permeable reaction wall, the functional materials are composed of activated carbon, clay, microbial inoculants, carbon sources, nitrogen sources, phosphorus sources, metal ions and essential nutrients for microorganisms, and the essential nutrients for microorganisms include water, growth factors and trace elements such as zinc, molybdenum, nickel and the like;

[0026] The waterproof wall causes the pollution plume to flow into the reaction wells, and the pollution plume is treated by the permeable reaction walls in sequence, wherein the zero-valent iron in the reaction wells of the first level of funnel-door permeable reaction wall reduces and removes part of the pollutants, and reduces the pollutants that are not suitable for direct oxidation into a form that is easy to be oxidized, to generate divalent iron;

[0027] The upstream residual pollutants and the divalent iron enter the reaction wells of the second level of funnel-door permeable reaction wall, the divalent iron and the citrate chelate to form an iron citrate chelating agent, the persulfate is activated by the iron citrate chelating agent to generate strong oxidizing sulfate radicals, so as to degrade chlorinated hydrocarbons in the pollution plume into inorganic small molecular substances;

[0028] The upstream water body enters the three-stage reaction well, residual organic matter and inorganic pollutants are adsorbed and biodegraded under the action of functional fillers, and the reaction well is intermittently aerated through an aeration device, and microbial agents are cultured on the biofilm filler to strengthen the degradation of organic matter in the pollution plume.

[0029] Compared with the prior art, the application has the following beneficial effects:

[0030] (1) For the remediation of chlorinated hydrocarbons, heavy metals and other pollutants in groundwater, a multi-stage aeration funnel-water gate type permeable reaction wall in-situ remediation method is disclosed, zero-valent iron, activated carbon and clay mixed fillers are filled in the first-stage reaction well, activated carbon adsorbs and captures pollutants, zero-valent iron reduces and removes the captured pollutants, and reduces pollutants that are not suitable for direct oxidation into a form that is easy to be oxidized, residual organic matter and ferrous iron flow into the second-stage reaction well; ferrous iron and citrate chelate form ferric citrate chelate, activate persulfate released by slow-release material to produce strong oxidizing sulfate radicals, and the sulfate radicals further oxidize and degrade residual pollutants into inorganic small molecules; inorganic small molecules and residual pollutants enter the third-stage reaction well, and are adsorbed and biodegraded under the action of functional fillers. In addition, the reaction well is intermittently aerated through an aeration device, microbial agents are cultured on the biofilm filler to strengthen the degradation and completely remove residual organic matter and inorganic pollutants in the groundwater, and purify the groundwater. The application uses stable, economical, efficient and safe mixed-slow-release-functional fillers to perform multi-stage synergistic treatment on organic matter, completely degrades and removes pollutants, can treat various organic matter and heavy metals at the same time, has the advantages of efficient remediation, strong applicability, ecological environmental protection and the like.

[0031] (2) Single reaction wells and impervious walls are alternately and spacedly arranged to form a reaction group well type PRB, a reaction unit assembly is placed in the reaction well, adjacent reaction units are connected through the end portions, the reaction unit has a moderate volume, a water-permeable geotextile is embedded around the inside of the reaction unit, and the geotextile is sealed after being filled with medium materials to prevent the medium materials from loosening and being lost. After the filling materials are filled on the ground, the reaction unit is lifted by hoisting equipment and placed in the reaction well; when the filling materials are used for a long time, the water quality decreases, the reaction unit is lifted by hoisting equipment and taken out of the reaction well, and new filling materials are replaced on the ground, so that the installation and operation and maintenance are convenient, the process is simple, and the engineering problems of replacement and operation and maintenance of traditional PRB reaction media are overcome.

[0032] (3) A reverse osmosis layer is arranged on the periphery of the pipeline to block the aquifer silt, so that the reaction well can be prevented from being blocked.

[0033] (4) Constructing a perennial deep-rooted plant planting zone, and placing the aeration pipe and biofilm carrier in the reaction well in the third funnel-door type permeable reaction wall, so that the chlorinated hydrocarbon organic matter biodegradation process is strengthened through the plant and microorganism coupling effect, and the pollutants in the groundwater are beneficially removed. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a plan view of the groundwater remediation device of the embodiment of the present application;

[0035] Figure 2 It is a schematic view of the reaction well structure of the embodiment of the present application;

[0036] Figure 3 It is a schematic view of the reaction unit in the reaction well of the embodiment of the present application;

[0037] Figure 4 It is a schematic view of the structure of the support frame, the aeration pipe and the biofilm of the embodiment of the present application.

[0038] In the figure: 1, permeable reaction wall; 11, waterproof wall; 12, reaction well; 121, pipeline; 122, reverse osmosis layer; 123, water inlet and outlet hole; 13, impermeable wall; 14, reaction unit; 141, hook; 142, filling material; 31, support frame; 32, biofilm carrier; 33, aeration pipe; 34, sample automatic detection and analysis device; 4, plant planting zone; 41, deep-rooted plant. DETAILED DESCRIPTION

[0039] The technical solutions of the present application will be described clearly and completely below in combination with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0040] From Figure 1 It can be seen that the groundwater remediation device of the embodiment comprises multiple levels of funnel-door type permeable reaction walls arranged at intervals, and any level of funnel-door type permeable reaction wall comprises a permeable reaction wall 1 and a waterproof wall 11 at both ends of the permeable reaction wall 1. The permeable reaction wall 1 is located downstream of the pollution plume, and the permeable reaction wall 1 is arranged perpendicular to the groundwater flow direction. The waterproof wall 11 can adopt a single-shaft or double-shaft mixing pile waterproof curtain, and the longitudinal depth penetrates the first layer of phreatic water-bearing layer and reaches at least 0.5 m below the relative waterproof layer; the waterproof wall 11 is inclined to the upstream outside of the permeable reaction wall 1, and the included angle with the permeable reaction wall 1 is 110-160°, and the length of the waterproof wall 11 at any end is greater than the length of the pollution plume by 1-2 m, so as to block the groundwater pollution plume from converging to the permeable reaction wall area.

[0041] For any stage funnel-gate permeable reactive barrier, the permeable reactive barrier is formed by alternately and spacedly arranging a plurality of reactive wells 12 and impervious walls 13, forming a permeable wall containing reactive cluster wells. The distance between adjacent reactive wells is 1-3 m, and the depth of the reactive well is greater than 0.5 m of the depth of the groundwater pollution. The reactive well 12 includes a pipe 121 vertically arranged and having a pipe cover at the upper and lower ends, and a reverse osmosis layer 122 composed of quartz sand and gravel surrounding the pipe 121. The diameter of the pipe 121 is 0.5-1.5 m, and the material is HDPE or PVC. A plurality of water inlet and outlet holes 123 are uniformly arranged on the lower part of the pipe wall of the pipe 121, and the hole diameter is 3 cm. In the reverse osmosis layer 122, the particle size of the quartz sand is 1-3 mm, and the particle size of the gravel is 1-3 cm, which is filled to a height of 0.5 m above the water inlet and outlet holes 121 of the pipe 121, so as to block the silt in the aquifer and prevent the water inlet and outlet holes 123 from being blocked; a clay layer with a thickness greater than 0.5 m is further filled in the upper part of the reverse osmosis layer 122. The impervious wall 13 is tightly connected with the well wall of the reactive well 12, and a single shaft or double shaft mixing pile water stop curtain can also be used, which has the same depth as the waterproof wall 11, so as to ensure that the pollution plume flows out to the downstream side after passing through the reactive well. Specifically, the impervious wall 13 is connected with the middle position of the well wall of the pipe 121 through the reverse osmosis layer 122, so as to separate the reactive well into a water inlet area on the upstream side and a water outlet area on the downstream side.

[0042] In any stage funnel-gate permeable reactive barrier, the permeable reactive barrier 1 is located downstream of the pollution plume, and a plurality of reaction unit assemblies are arranged in the reactive well 12. The reaction unit 14 is a circular frame formed by welding a plurality of stainless steel solid pipes along the circumference. At least two hooks 141 are arranged at the two ends of the solid pipe at the bottom of the circular frame in the radial direction. The adjacent reaction units are connected in series by the hooks, so as to maintain the stable arrangement of the reaction units. The diameter of the reaction unit is 0.2-0.9 m. The reaction unit 14 is embedded with water permeable geotextile around the inside. The reaction unit is layered and arranged in the reactive well 12, and the height needs to reach 0.5 m above the groundwater depth in the reactive well 12. The reaction unit 14 can be filled with materials on the ground, and then hoisted into the reactive well one by one by the hoisting equipment on the ground, so as to complete the loading of the filling materials.

[0043] The filling materials 142 in the reaction units of the funnel-gate permeable reactive barrier at each stage are different. The reaction unit space in the first-stage funnel-gate permeable reactive barrier 100 is filled with mixed materials, and the mass ratio of the mixed materials is 1:0.5-2:0.5-2. The mixed materials are composed of zero-valent iron, activated carbon and clay. The zero-valent iron reduces and removes part of the pollutants, and reduces the pollutants that are not easy to be oxidized into a form that is easy to be oxidized, while generating divalent iron. The residual pollutants and divalent iron flow into the second-stage funnel-gate permeable reactive barrier;

[0044] The secondary funnel-gate type permeable reaction wall 200 is arranged downstream of the primary funnel-gate type permeable reaction wall 100, and the reaction unit space in the secondary funnel-gate type permeable reaction wall is filled with slow-release materials; the slow-release materials in the reaction unit of the secondary reaction well are composed of persulfate and citrate slow-release materials, and the mass ratio is 1:1, and the pH range of the persulfate released by the slow-release materials and wrapped in the core is between 6.0 and 7.8. The slow-release materials can effectively reduce the dissolution rate of persulfate and citrate and prolong the service life of the permeable reaction wall. Specifically, the persulfate is sodium persulfate, and the citrate is sodium citrate. The slow-release materials are spherical or cylindrical, with a diameter of 15-20 mm, and are mainly composed of sodium persulfate or sodium citrate, stable solidifying adhesive, zeolite and water, and the mass ratio is 1:1.2-1.8:0.5-0.8:0.9-1.1. The stable solidifying adhesive is cement and fine sand, and the mass ratio is 1:0.15-0.2. The upstream residual pollutants and divalent iron enter the secondary funnel-gate type permeable reaction wall, the divalent iron and sodium citrate are chelated to form ferric citrate chelate, and between pH=6.0-7.8, the persulfate slow-release material releases persulfate, and the persulfate is activated by the chelated divalent iron (i.e. ferric citrate chelate) to produce strong oxidizing sulfate radicals, oxidizing pollutants, and degrading chlorinated hydrocarbons in groundwater into inorganic small molecules.

[0045] The tertiary funnel-gate type permeable reaction wall 300 is arranged downstream of the secondary funnel-gate type permeable reaction wall 200, and the reaction unit space of the reaction well in the tertiary funnel-gate type permeable reaction wall is filled with functional materials; the functional materials in the reaction unit of the tertiary reaction well are composed of activated carbon, clay, microbial inoculum, carbon source, nitrogen source, phosphorus source, metal ion, and essential nutrients for microorganisms, etc.; the essential nutrients for microorganisms include water, growth factors, and trace elements such as zinc, molybdenum, nickel, etc.; the mass ratio of activated carbon and clay is 1:1, and the carbon source, nitrogen source, and phosphorus source in each kilogram of solid material contain 0-120 g / kg, 0-12 g / kg, and 0-6 g / kg, respectively; the metal ion contains 0.15-2.0 g MgSO4·7H2O, 0.15-2.0 g KH2PO4, and 0.06-1.2 g CaCl2; the essential nutrients for microorganisms contain 0.8-5.5 ml / kg; and the amount of microbial inoculum is appropriate.

[0046] In the tertiary funnel-gate type permeable reaction wall 300, biological membrane fillers are arranged around the reaction unit. An aeration pipe and a sample automatic detection and analysis device are arranged in the reaction well and fixed on one side of the reaction unit. The aeration pipe is connected with the air compressor on the ground and automatically controlled by the PLC system of the aeration device. The upstream water body enters the tertiary funnel-gate type permeable reaction wall, and residual organic matter and inorganic pollutants are adsorbed and biodegraded under the action of the functional fillers. In addition, the reaction well is intermittently aerated by the aeration device, and microbial agents are attached to the biological membrane fillers to strengthen the degradation of organic matter in the groundwater and purify the groundwater. When the fillers are used for a long time, the water quality decreases, and new fillers can be replaced.

[0047] In the tertiary funnel-gate type permeable reaction wall, as shown in Figure 3 The outer side of the reaction unit 14 is provided with a support frame 31, which is vertically welded on the outer side of the reaction unit by a plurality of stainless steel solid pipes. The diameter of the support frame 31 is 0.2-0.9 m, which is greater than the outer diameter of the reaction unit 14, and is used for hanging biological membrane fillers 32. The biological membrane fillers 32 are soft, semi-soft or other fillers, such as hollow biomimetic carbon fiber water grass.

[0048] The aeration pipe 33 and the sample automatic detection and analysis device 34 can be fixed on the support frame 31 outside the reaction unit by pipe clamps. The aeration pipe is installed on the upstream side and the bottom of the reaction well. The diameter of the aeration pipe is 5-10 cm, and the aeration holes with a diameter of 5 mm are uniformly arranged on the aeration pipe. The aeration pipe is connected with the air compressor on the ground through a valve and automatically controlled by the PLC system. The sample automatic detection and analysis device 34 can realize automatic collection of multi-layer samples and sample detection and analysis to evaluate the repair effect of the device.

[0049] The sample automatic detection and analysis device 34 mainly acquires water samples through various sensors and detection instruments, and then analyzes various indicators of the water body, including conductivity sensor, dissolved oxygen sensor, COD sensor, NH3-N sensor, microorganism (BOD) sensor, free radical sensor, organic matter detector, A / D converter; the groundwater quality detection information is input into the PLC control system through the A / D converter.

[0050] Further, a plant planting belt 4 can be constructed between the secondary and tertiary permeable reaction walls to repair the organic matter contaminated soil by plant repair. The planting belt plants perennial deep-rooted plants 41, and the roots of the plants are inoculated with iron-tolerant ectomycorrhizae. The planting soil is adjusted in pH by using magnesium peroxide alkaline oxide to prevent soil acidification.

[0051] The perennial deep-rooted plants are one or more of mulberry, sycamore, kapok, white wax, camphor tree, ailanthus, and pine. The planting density is 3x3-7x7 m2. The addition amount of the iron-tolerant ectomycorrhizae is 0.1%-1%.

[0052] Of course, the present application can have other various embodiments and can be carried out in various concretizations without departing from the scope of the application; and anyone skilled in the art, based on the present application, can make various corresponding changes and modifications, which are all within the scope of the claims of the present application.

Claims

1. A groundwater remediation apparatus, characterized by, The funnel-gate type permeable reactive wall comprises multiple levels of funnel-gate type permeable reactive walls arranged at intervals downstream from the pollution plume, and each level of funnel-gate type permeable reactive wall comprises: The permeable reactive wall is arranged vertically to the groundwater flow direction and comprises alternately connected reaction wells and impervious walls, and a plurality of reaction units are arranged in series in the reaction wells, and a water-permeable geotextile is embedded around the inside of the reaction units; The reaction units in the first level of funnel-gate type permeable reactive wall are filled with mixed materials, and the mixed materials are mixed from zero-valent iron, activated carbon and clay; The reaction units in the second level of funnel-gate type permeable reactive wall are filled with slow-release materials, and the slow-release materials are composed of persulfate and citrate slow-release materials; The reaction units in the third level of funnel-gate type permeable reactive wall are filled with functional materials, and the functional materials are composed of activated carbon, clay, microbial inoculum, carbon source, nitrogen source, phosphorus source, metal ions and essential nutrients for microorganisms; The water-resisting wall is connected to both ends of the permeable reactive wall, the reaction well comprises a pipe arranged vertically and having pipe covers at the upper and lower ends, and a reverse osmosis layer composed of quartz sand and gravel surrounding the pipe, the impervious wall is lapped between the reverse osmosis layer and the outer wall of the pipe, and a plurality of water inlet and outlet holes are uniformly arranged in the lower part of the pipe wall, A plant planting zone is constructed between the permeable reactive walls of the second and third levels of funnel-gate type permeable reactive wall, The water-resisting wall causes the pollution plume to flow into the reaction well, and the pollution plume is treated by the permeable reactive wall in sequence, wherein the zero-valent iron in the reaction well of the first level of funnel-gate type permeable reactive wall reduces and removes part of the pollutants, and reduces the pollutants that are not suitable for direct oxidation into a form that is easy to be oxidized, and generates ferrous iron at the same time; The upstream residual pollutants and ferrous iron enter the reaction well of the second level of funnel-gate type permeable reactive wall, the ferrous iron and citrate chelate form ferric citrate chelator, and the persulfate is activated by the ferric citrate chelator to generate strong oxidizing sulfate radicals, so as to degrade chlorinated hydrocarbons in the pollution plume into inorganic small molecule substances; The water body enters the third level of reaction well, residual organic matter and inorganic pollutants are adsorbed and biodegraded under the action of functional fillers, and the microbial inoculum is hung on the biofilm filler to strengthen the degradation of organic matter in the pollution plume through the intermittent aeration of the aeration device to the reaction well.

2. The groundwater remediation device of claim 1, wherein The distance between adjacent reaction wells is 1-3 m, the depth of the reaction well is greater than 0.5 m of the groundwater pollution depth, the particle size of the quartz sand of the reverse osmosis layer is 1-3 mm, the particle size of the gravel is 1-3 cm, the reverse osmosis layer is filled to 0.5 m above the water inlet and outlet hole area of the pipe, and the upper part of the reverse osmosis layer is further filled with clay with a height greater than 0.5 m.

3. The groundwater remediation device of claim 2, wherein The diameter of the pipe is 0.5-1.5 m, and the material is HDPE or PVC, and the impervious wall and the water-resisting wall have the same depth, so as to separate the reaction well into a water inlet area on the upstream side and a water outlet area on the downstream side.

4. The groundwater remediation device of claim 1, wherein The water-resisting wall and the impervious wall adopt single-shaft or double-shaft mixing pile water-stop curtain, the longitudinal depth penetrates the first layer of phreatic water-bearing layer and reaches at least 0.5 m below the relative water-resisting layer, the water-resisting wall is inclined to the upstream side of the permeable reactive wall, and the included angle with the permeable reactive wall is 110-160°, and the length of the water-resisting wall at either end exceeds the pollution plume by 1-2 m.

5. The groundwater remediation device of claim 1, wherein The mass ratio of the zero-valent iron, the activated carbon and the clay in the mixed material is 1:0.5-2:0.5-2; The mass ratio of the persulfate and the citrate salt in the slow-release material is 1:1, and the slow-release filler releases the persulfate in the core in a pH range of 6.0-7.8; The mass ratio of the activated carbon and the clay in the functional material is 1:1, and each kilogram of the solid material contains 0-120 g / kg of a carbon source, 0-12 g / kg of a nitrogen source, 0-6 g / kg of a phosphorus source, 0.15-2.0 g of MgSO4·7H2O, 0.15-2.0 g of KH2PO4, 0.06-1.2 g of CaCl2, 0.8-5.5 ml / kg of essential nutrient elements for microorganisms, and a microbial agent.

6. The groundwater remediation device of claim 1, wherein, The reaction unit is a round frame welded by a stainless steel solid tube, the diameter of the reaction unit is 0.2-0.9 m, the length is 0.5-1 m, the end portions of adjacent reaction units are connected by a hook, so that the adjacent reaction units are connected in series as a reaction unit assembly, and the height of the reaction unit assembly reaches 0.5 m above the water depth of the underground water in the reaction well.

7. The groundwater remediation device of claim 1, wherein A support frame is arranged on the outer periphery of the reaction unit of the three-stage funnel-gate permeable reaction wall, and is used for suspending a biological membrane filling material, and the biological membrane filling material is a soft or semi-soft filling material.

8. The groundwater remediation device of claim 7, wherein, An aeration pipe and a sample automatic detection and analysis device are further arranged on the support frame, the aeration pipe is installed on the upstream side and the bottom of the reaction well, the aeration pipe is connected to an air compressor through a valve, and the sample automatic detection and analysis device is used for automatic collection, detection and analysis of water quality samples in multiple layers.

9. The groundwater remediation device of claim 1, wherein, The plant planting zone is planted with perennial deep-rooted plants, the roots of the plants are inoculated with iron-tolerant ectomycorrhiza, the planting soil is adjusted in pH by using magnesium peroxide alkaline oxide, the perennial deep-rooted plants are one or more of mulberry, sycamore, kapok, white wax, camphor tree, ailanthus, and pine; the planting density is 3x3-7x7 m 2 ; the iron-tolerant ectomycorrhiza is added in an amount of 0.1%-1%.

10. A groundwater remediation method characterized by, Comprise: A plurality of three-stage funnel-gate permeable reaction walls are arranged downstream of the pollution plume, each three-stage funnel-gate permeable reaction wall comprises a permeable reaction wall and a waterproof wall connected to both ends of the permeable reaction wall, the permeable reaction wall is arranged perpendicular to the direction of underground water flow, and comprises reaction wells and impervious walls connected in alternation, and a plurality of reaction units are arranged in series in the reaction wells; The mixed material is mixed by zero-valent iron, activated carbon and clay; the slow-release material in the reaction units of the second-stage funnel-gate permeable reaction wall is composed of persulfate and citrate salt slow-release material; and the functional material in the reaction units of the third-stage funnel-gate permeable reaction wall is composed of activated carbon, clay, a microbial agent, a carbon source, a nitrogen source, a phosphorus source, metal ions and essential nutrient elements for microorganisms; The waterproof wall causes the pollution plume to flow into the reaction wells, and the pollution plume is treated by the permeable reaction walls in sequence, wherein the zero-valent iron in the reaction wells of the first-stage funnel-gate permeable reaction wall reduces and removes part of the pollutants, and reduces the pollutants that are not suitable for direct oxidation into a form that is easy to be oxidized, and generates ferrous iron at the same time; The upstream residual pollutants and the ferrous iron enter the reaction wells of the second-stage funnel-gate permeable reaction wall, the ferrous iron and the citrate salt are chelated to form ferric citrate chelator, the persulfate is activated by the ferric citrate chelator to generate strong oxidizing sulfate radicals, so that the chlorinated hydrocarbons in the pollution plume are degraded into inorganic small molecular substances; Water enters the tertiary reaction well, residual organic matter and inorganic pollutants under the action of functional filler adsorption and biodegradation, and through the aeration device to the reaction well intermittent aeration, microbial inoculum on the biofilm filler on the film, strengthen the degradation of organic matter in pollution plume.

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