A dynamic simulation experimental system and method for groundwater circulation well

Abstract

The present invention relates to the technical field of groundwater circulation wells, and discloses a dynamic simulation experimental system and method for groundwater circulation wells. A dynamic simulation experimental system for groundwater circulation wells comprises a seepage trough, a base, a circulation well and a drug injection well; the seepage trough comprises a rectangular shell with an upper opening and a water-containing medium arranged in the shell; the circulation well comprises a first circular tube vertically arranged at the center of the seepage trough, and the first circular tube is connected from bottom to top by a lower solid tube, a lower screen tube, a middle solid tube, an upper screen tube and an upper solid tube; a waterproof transverse partition is horizontally arranged in the middle of the middle solid tube; the drug injection well comprises a second circular tube arranged in the seepage trough. The present invention can simulate the hydraulic circulation characteristics of groundwater circulation wells under various conditions, accurately monitor and expand the influence radius of groundwater circulation wells, and simulate the repair experiments of groundwater circulation wells under various conditions, providing a theoretical basis and technical support for the research and promotion and application of groundwater circulation well repair technology.

Description

Technical Field

[0001] The invention relates to the technical field of groundwater circulation wells, and in particular to a dynamic simulation experimental system and method for a groundwater circulation well. Background Art

[0002] Groundwater is an important component of freshwater resources and plays a vital role in the development of human society. However, with the development of my country's industry, the pollution of soil and groundwater by non-aqueous phase liquids (NAPL) represented by petroleum pollutants has become increasingly serious.

[0003] For such groundwater organic pollutants, groundwater circulation well (GCW) technology has the advantages of high removal efficiency, short remediation cycle, and easy control of secondary pollution, and has great development potential and broad application prospects. Over the years, many scientific researchers have continuously carried out research on the remediation of organic pollutants using groundwater circulation wells, but due to the large differences in hydrogeological conditions and pollutant properties of different groundwater pollution sites, the types of groundwater circulation wells suitable for different sites are very different.

[0004] Up to now, the research and application of GCW remediation technology in my country is still in its infancy, and related research work is mostly limited to indoor experiments and numerical simulations, and there are no mature GCW remediation technology application cases. Although numerical simulation is not limited by experimental conditions, the errors of simulation results are relatively large because the site boundary conditions and water-containing medium properties are often simplified; and the results and accuracy obtained are different due to different forms of structural discretization, and the randomness is relatively large.

[0005] In addition, studies have shown that groundwater circulation wells are suitable for aquifers with high horizontal permeability (>0.30m / d) and an anisotropy of 3-10. When the anisotropy of the aquifer is greater than 10, the circulation well will not be able to operate. For this reason, groundwater circulation wells in low permeability aquifers often encounter problems such as too small influence radius and too low pollutant remediation efficiency. How to increase the influence radius of the circulation well and expand the hydraulic circulation range is one of the factors currently restricting the development of circulation well technology. Summary of the invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a dynamic simulation experimental system and method for a groundwater circulation well, which can simulate the hydraulic circulation characteristics of the groundwater circulation well under a variety of different conditions (different water-containing media, different groundwater flow rates, different circulation well structures, and different circulation modes), can accurately monitor and expand the influence radius of the groundwater circulation well, and can simulate the remediation experiments of groundwater circulation wells for organic pollutants of different properties under a variety of different conditions, solving the problem that the prior art cannot comprehensively and accurately study the dynamic remediation process of groundwater circulation wells for organic pollutants, and has the advantages of reasonable structure, simple operation, high efficiency and practicality.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions to achieve it.

[0008] A dynamic simulation experimental system for a groundwater circulation well, comprising a seepage trough, a base, a circulation well and a drug injection well;

[0009] The seepage trough comprises a rectangular shell with an upper opening and a water-containing medium arranged in the shell; a first water outlet is arranged at the upper end of the right wall of the shell, a first water inlet is arranged at the lower end of the left wall of the shell, and a first drain outlet is arranged at the bottom of the shell near the first water inlet; a first baffle is vertically arranged near the first water outlet in the shell, a second baffle is vertically arranged near the first water inlet in the shell, a plurality of holes are respectively arranged on the first baffle and the second baffle, the lower ends of the first baffle and the second baffle are respectively fixedly connected to the upper surface of the bottom wall of the shell, and the front and rear sides of the first baffle and the second baffle are respectively fixedly connected to the front wall and the rear wall of the shell. The first baffle and the second baffle are connected in a fixed manner, the height of the first baffle and the second baffle is flush with the first water inlet, and a water supply compartment is formed between the first baffle and the right wall of the shell and between the second baffle and the left wall of the shell respectively; a plurality of second water outlets are arranged on the front wall of the shell between the first baffle and the second baffle; a plurality of sampling ports are arranged on the rear wall of the shell between the first baffle and the second baffle, and the sampling ports are provided with sampling pipes, and valves are arranged on the sampling pipes; a first peristaltic pump for adding water and a second peristaltic pump for adding pollutants are also included, and the first water inlet is connected to the water outlets of the first peristaltic pump and the second peristaltic pump respectively through connecting pipes;

[0010] The base is arranged at the bottom of the shell, and the lower surface of the bottom wall of the shell is fixedly connected to the upper surface of the base; a pressure measuring plate is also arranged on the upper surface of the base, and a plurality of pressure measuring tubes are vertically arranged on the upper surface of the pressure measuring plate; the plurality of second water outlets are respectively connected to the lower ends of the plurality of pressure measuring tubes through pipelines;

[0011] The circulation well comprises a first circular tube vertically arranged on the bottom surface of the seepage groove, a top cover is arranged on the top of the first circular tube, and the bottom is closed; the first circular tube is connected from bottom to top by a lower solid tube, a lower screen tube, a middle solid tube, an upper screen tube and an upper solid tube; the tube walls of the lower solid tube, the middle solid tube and the upper solid tube are watertight, and the tube walls of the lower screen tube and the upper screen tube are provided with a plurality of water-permeable holes; a watertight transverse partition is horizontally arranged in the middle of the middle solid tube; a coaxial first pipeline is arranged at the center of the first circular tube, and the lower end of the first pipeline passes through the top cover and the transverse partition in sequence and extends downward to the lower screen tube; a second pipeline is also included, and the lower end of the second pipeline passes through the top cover and extends downward to the upper screen tube; a circulation pump is also included, and the upper end of the first pipeline is connected to the water inlet of the circulation pump; the upper end of the second pipeline is connected to the water outlet of the circulation pump;

[0012] The injection well includes a second circular tube; the second circular tube is vertically arranged on one side of the first circular tube in the seepage trough, the bottom of the second circular tube is closed, and the wall of the second circular tube is provided with multiple permeable sieve holes. It also includes a dosing tube and a third peristaltic pump. The front end of the dosing tube is connected to the output end of the third peristaltic pump, and the end of the dosing tube extends into the second circular tube.

[0013] Preferably, the number of the second water outlets is 50, which are evenly arranged in 5 rows from top to bottom, and there are 10 second water outlets in each row evenly arranged from left to right, and the distance between two adjacent second water outlets is 100 mm.

[0014] Preferably, the number of the pressure measuring tubes is 50.

[0015] Preferably, the number of sampling ports is 50, which are evenly arranged in 5 rows from top to bottom, with 10 sampling ports evenly arranged in each row from left to right, and the distance between two adjacent sampling ports is 100 mm.

[0016] Preferably, the base is a stainless steel bracket, and a sliding wheel is arranged on the outer side of the lower surface of the stainless steel bracket.

[0017] Preferably, a stainless steel screen or a nylon screen is respectively provided on the right side of the first baffle and the left side of the second baffle.

[0018] Preferably, the outer side walls of the first circular tube and the second circular tube are respectively provided with a stainless steel screen or a nylon screen.

[0019] Preferably, the water-containing medium includes any one or more of coarse sand, medium sand, fine sand, silt sand or clay.

[0020] A dynamic simulation experimental method for a groundwater circulation well comprises the following steps:

[0021] Step 1, placing a circulation well and a drug injection well in the seepage trough, and then filling the seepage trough with water-containing medium;

[0022] Step 2, start the first peristaltic pump to pass water into the seepage tank to simulate groundwater, start the circulation pump to start the circulation well after the water-containing medium is saturated with water, add an equal amount of tracer every 100 mm in the horizontal direction at 50 mm below the upper surface of the water-containing medium, and trace the hydraulic circulation characteristics of the groundwater in the circulation well;

[0023] Step 3: After the circulation well runs stably, observe the water level change amplitude in each piezometer, and calculate the influence radius of the circulation well by measuring the distance between the two piezometers in the same row where the water level changes significantly and are farthest from the circulation well;

[0024] Step 4, turning off the circulation pump and turning on the second peristaltic pump to release a supersaturated solution of organic pollutants with a known concentration from the first water inlet of the seepage tank to simulate the migration process of organic pollutants in different aqueous media;

[0025] Step 5, turn off the second peristaltic pump, take samples to determine the concentration of pollutants in the groundwater; turn on the circulation pump to start the circulation well, turn on the third peristaltic pump after the circulation well runs stably, and transport the agent to the aqueous medium. Then turn off the circulation pump and the third peristaltic pump, take samples to analyze the concentration of pollutants in the groundwater, and obtain the remediation efficiency of the groundwater circulation well for the organic pollutants.

[0026] Further preferably, step 6 is included, wherein the circulation pump in steps 1 to 3 is replaced with a variable frequency pump to adjust the circulation flow rate of groundwater in the water-containing medium; or an external high-pressure water gun is connected in steps 1 to 3, and the high-pressure water generated by the high-pressure water gun is directly applied to the water-containing medium 12 in the seepage trough 1 to change the porosity or permeability coefficient of the water-containing medium, and a simulation experiment of amplifying the influence radius of the groundwater circulation well is conducted.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The groundwater circulation well dynamic simulation experimental system and method of the present invention can accurately simulate the remediation experiments of groundwater circulation wells for organic pollutants of various properties under various conditions (different water-containing media, different groundwater flow rates, different circulation well structures, and different circulation modes). The experimental device has diverse functions and can comprehensively and accurately simulate the dynamic remediation process of groundwater circulation wells for organic pollutants, accurately monitor and expand the influence radius of groundwater circulation wells, and can provide a theoretical basis and technical support for the research and promotion and application of groundwater circulation well remediation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Figure 1 It is a schematic diagram of the overall structure of the simulation experiment system of the present invention;

[0031] Figure 2 It is the left view of the simulation experimental system;

[0032] Figure 3 It is the top view of the simulation experimental system;

[0033] Figure 4 It is the structural schematic diagram of the circulation well;

[0034] Figure 5 It is a structural schematic diagram of the injection well;

[0035] Figure 6 This is a schematic diagram of the three-dimensional elliptical flow field after the circulation well runs stably;

[0036] The accompanying drawings are marked as follows: 1. Seepage trough, 2. Base, 3. Circulation well, 4. Injection well, 11. Shell, 12. Aqueous medium, 13. First water outlet, 14. First water inlet, 15. First drain outlet, 16. First baffle, 17. Second baffle, 18. Second water outlet, 19. Sampling port, 21. Pressure plate, 22. Pressure tube, 31. First circular tube, 32. Partition, 33. First pipeline, 34. Second pipeline, 35. Lower solid tube, 36. Lower screen tube, 37. Middle solid tube, 38. Upper screen tube, 39. Upper solid tube, 41. Second circular tube, 42. Permeable sieve hole, 43. Dosing tube. DETAILED DESCRIPTION

[0037] The embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0038] refer to Figure 1 , which is a schematic diagram of the overall structure of the simulation experiment system of the present invention. Figure 2 and Figure 3 They are the left view and top view of the experimental system respectively.

[0039] A dynamic simulation experimental system for a groundwater circulation well, comprising a seepage trough 1, a base 2, a circulation well 3 and a drug injection well 4;

[0040] The seepage trough 1 comprises a rectangular shell 11 with an upper opening and an aqueous medium 12 arranged in the shell; it also comprises a first peristaltic pump for adding water and a second peristaltic pump for adding pollutants; a first water outlet 13 is arranged at the upper end of the right wall of the shell, and the first water outlet 13 is provided with a first water outlet pipe, and a valve is arranged on the first water outlet pipe; a first water inlet 14 is arranged at the lower end of the left wall of the shell, and the first water inlet 14 is connected to the water outlets of the first peristaltic pump and the second peristaltic pump respectively through connecting pipes, and a valve is arranged on the connecting pipe; a first drain outlet 15 is arranged at the bottom of the shell near the first water inlet; a first baffle 16 is vertically arranged near the first water outlet in the shell, and a second baffle 17 is vertically arranged near the first water inlet in the shell, and a plurality of holes are respectively arranged on the first baffle and the second baffle, and in order to prevent the aqueous medium from entering the water supply compartment, a stainless steel screen or a nylon screen is respectively arranged on the right side of the first baffle and the left side of the second baffle.

[0041] The lower ends of the first baffle 16 and the second baffle 17 are respectively fixedly connected to the upper surface of the bottom wall of the shell, and the front and rear sides of the first baffle 16 and the second baffle 17 are respectively fixedly connected to the front wall and the rear wall of the shell, and the height of the first baffle 16 and the second baffle 17 is flush with the first water inlet, and a water supply compartment is formed between the first baffle and the right wall of the shell and between the second baffle and the left wall of the shell; the water outlet of the first peristaltic pump is connected to the first water inlet through a pipeline, and the first peristaltic pump inputs distilled water into the water supply compartment between the first baffle and the left wall of the shell, and the distilled water gradually drives out the air in the pores of the water-containing medium and infiltrates the water-containing medium. In this embodiment, distilled water is used to simulate groundwater.

[0042] A plurality of second water outlets 18 are provided on the front wall of the shell 11 between the first baffle 16 and the second baffle 17; a plurality of sampling ports 19 are provided on the rear wall of the shell 11 between the first baffle 16 and the second baffle 17, and the sampling ports are provided with sampling pipes, and valves are provided on the sampling pipes. The sampling ports are used to take water samples and determine the concentration of pollutants therein.

[0043] The base is arranged at the bottom of the shell 11, and the lower surface of the bottom wall of the shell 11 is fixedly connected to the upper surface of the base 2; a pressure measuring plate 21 is also arranged on the upper surface of the base 2, and a plurality of pressure measuring tubes 22 are vertically arranged on the upper edge of the pressure measuring plate; a plurality of second water outlets 18 are respectively connected to the lower ends of a plurality of pressure measuring tubes through pipes; the pressure measuring tubes are used to display the water levels of the plurality of second water outlets, and the water level value of the pressure measuring tube is recorded after the water level is stable.

[0044] Specifically, the seepage trough is made of organic glass, the shell size is 1200mm×400mm×600mm, the base is a stainless steel bracket with sliding wheels, and there are water supply compartments with a width of 100mm on the left and right sides of the seepage trough. In order to simulate different water-containing media, any one of coarse sand, medium sand, fine sand, silt sand or clay can be used to simulate a homogeneous groundwater aquifer, and a heterogeneous groundwater aquifer can also be simulated by different combinations of multiple water-containing media. The first water inlet can be connected to a first peristaltic pump with adjustable flow through a hose, so as to simulate different groundwater flow rates. In this embodiment, the hose is a latex tube.

[0045] Specifically, in order to measure the influence radius of the groundwater circulation well, 50 second water outlets are arranged on the front wall of the shell between the first baffle and the second baffle, with a total of 5 rows and 10 columns, and the spacing is 100mm. From top to bottom, from left to right, they are 1-5 rows and 1-10 columns respectively. 50 glass pressure tubes are arranged vertically on the upper edge of the side pressure plate. The above 50 second water outlets are connected to the lower part of the 50 glass pressure tubes through latex tubes, and the top of the pressure tubes is connected to the atmosphere to facilitate the discharge of air in the pores of the water-containing medium; 50 sampling ports are arranged on the rear wall of the shell between the first baffle and the second baffle, with a total of 5 rows and 10 columns, and the spacing is 100mm. From top to bottom, from left to right, they are 1-5 rows and 1-10 columns respectively, which are used to take water samples and measure the concentration of pollutants therein.

[0046] refer to Figure 4 , is a schematic diagram of the structure of the circulation well; the circulation well 3 includes a first circular tube 31 vertically arranged on the bottom surface of the seepage groove 1, a top cover is arranged on the top of the first circular tube 31, and the bottom is closed; the first circular tube 31 is connected from bottom to top by a lower solid tube 35, a lower screen tube 36, a middle solid tube 37, an upper screen tube 38 and an upper solid tube 39; the walls of the lower solid tube, the middle solid tube and the upper solid tube are watertight, and the walls of the lower screen tube and the upper screen tube are provided with a plurality of water-permeable holes; a watertight transverse partition 32 is horizontally arranged in the middle of the middle solid tube 37; a coaxial first pipe 33 is arranged at the center of the first circular tube, and the lower end of the first pipe 33 passes through the top cover and the transverse partition 32 in sequence and extends downward to the lower screen tube 36; it also includes a second pipe 34, the lower end of the second pipe 34 passes through the top cover and extends downward to the upper screen tube 38; it also includes a circulation pump,

[0047] The upper end of the first pipe 33 is connected to the water inlet of the circulation pump; the upper end of the second pipe 34 is connected to the water outlet of the circulation pump; the connection mode of the circulation pump is changeable. The position of the first circular pipe 31 in the seepage tank 1 can be moved as needed.

[0048] Specifically, the circulation well adopts an organic glass round tube with a diameter of 200-300 mm and a height of 600-900 mm, and the outer wall of the organic glass round tube is provided with a stainless steel screen or a nylon screen; in order to simulate circulation wells with different structures, the organic glass round tube is designed to be composed of 5 independent round tubes connected by buckles, from bottom to top, they are respectively a lower solid tube 35, a lower screen tube 36, a middle solid tube 37, an upper screen tube 38 and an upper solid tube 39, wherein the walls of the lower solid tube, the middle solid tube and the upper solid tube are impermeable, and the walls of the lower screen tube and the upper screen tube are provided with a plurality of water-permeable holes; the upper screen tube and the lower screen tube can be provided with different screen hole diameters or hole spacings, and the upper screen tube, the lower screen tube, the upper solid tube and the lower solid tube can select different heights to realize the change of the position and quantity of the solid tube and the screen tube of the circulation well.

[0049] The hydraulic circulation of the circulation well includes two modes: positive circulation and reverse circulation. In the positive circulation mode, the upper end of the first pipe is connected to the water inlet of the circulation pump, and the upper end of the second pipe is connected to the water outlet of the circulation pump. Water flows in from the lower screen pipe and flows out from the upper screen pipe. The flow direction outside the well is from top to bottom, thus forming an elliptical flow field around the circulation well. In the reverse circulation mode, the upper end of the second pipe is connected to the water inlet of the circulation pump, and the upper end of the first pipe is connected to the water outlet of the circulation pump, so that the flow direction of water inside and outside the well is opposite to the positive circulation. Figure 6 The figure shows a schematic diagram of a three-dimensional elliptical flow field after the circulation well is stabilized. By changing the connection mode between the circulation pump and the first pipeline and the second pipeline, the hydraulic circulation operation mode of the circulation well can be switched.

[0050] Figure 5 The schematic diagram of the structure of the injection well. The injection well 4 includes a second circular tube 41; the second circular tube 41 is vertically arranged on one side of the first circular tube 31 in the seepage trough 1, the bottom of the second circular tube 41 is closed, and the wall of the second circular tube is provided with a plurality of water-permeable sieve holes 42, and also includes a dosing tube 43 and a third peristaltic pump 44, the head end of the dosing tube is connected to the output end of the third peristaltic pump, and the end of the dosing tube extends into the second circular tube. The position of the second circular tube 41 in the seepage trough 1 is movable.

[0051] Specifically, the injection well uses an organic glass round tube with a diameter of 100-200mm and a height of 600-900mm. A plurality of water-permeable sieve holes are arranged on the tube wall below 550mm in height of the organic glass round tube, and a stainless steel sieve or a nylon sieve is arranged on the outer wall of the organic glass round tube. The organic glass round tube can be provided with water-permeable sieve holes with different aperture sizes or hole spacings.

[0052] A dynamic simulation experimental method for a groundwater circulation well comprises the following steps:

[0053] Step 1, placing a circulation well and a drug injection well in the seepage trough, and then filling the seepage trough with water-containing medium;

[0054] In order to simulate different water-containing media, any one of coarse sand, medium sand, fine sand, silt or clay can be selected to simulate a homogeneous groundwater aquifer, or a heterogeneous groundwater aquifer can be simulated by different combinations of multiple water-containing media. Before filling the sand, the location of the circulation well and the injection well must be determined first, and the circulation well and the injection well must be placed; then the selected water-containing medium or water-containing medium combination can be filled layer by layer in the seepage trough, with a filling height of 550mm. During the filling process, the water-containing medium is continuously compacted to ensure uniform filling of the medium on the one hand, and to ensure that the circulation well and the injection well are firmly fixed on the other hand.

[0055] Step 2, start the first peristaltic pump to pass water into the seepage tank to simulate groundwater, start the circulation pump to start the circulation well after the water-containing medium is saturated with water, add an equal amount of tracer every 100 mm in the horizontal direction at 50 mm below the upper surface of the water-containing medium, and trace the hydraulic circulation characteristics of the groundwater in the circulation well;

[0056] In this embodiment, distilled water is introduced into the seepage trough to simulate groundwater. Specifically, the first water inlet is connected to the first peristaltic pump so that the distilled water is evenly and slowly filled into the water supply compartment, gradually displacing the air in the pores of the water-containing medium. When the top surface of the water-containing medium is completely wetted and a thin layer of water overflows, the medium is completely saturated with water, and the water levels of the pressure measuring tubes should remain flush. By adjusting the flow rate of the first peristaltic pump, different groundwater flow rates can be simulated, and at the same time, the valve of the first water outlet is controlled so that the water level fluctuation amplitude of the water supply compartments on both sides does not exceed 5mm. After the groundwater flow rate stabilizes, the circulation pump is turned on, and the circulation well starts to run. An equal amount of tracer is added every 100mm in the horizontal direction at 50mm below the upper surface of the water-containing medium through a long needle tube. Due to the indicating effect of the tracer, the groundwater will form a visual elliptical flow field around the circulation well, such as Figure 6 As shown in the figure, the elliptical flow field will gradually expand as the simulated circulation well runs longer.

[0057] The hydraulic circulation of the circulation well includes two modes: positive circulation and reverse circulation. In the positive circulation mode, the upper end of the first pipe is connected to the water inlet of the circulation pump, and the upper end of the second pipe is connected to the water outlet of the circulation pump. Water flows in from the lower screen pipe and flows out from the upper screen pipe. The flow direction outside the well is from top to bottom, thus forming an elliptical flow field around the circulation well. In the reverse circulation mode, the upper end of the second pipe is connected to the water inlet of the circulation pump, and the upper end of the first pipe is connected to the water outlet of the circulation pump, so that the flow direction of water inside and outside the well is opposite to the positive circulation. By changing the connection method of the circulation pump with the first pipe and the second pipe, the hydraulic circulation operation mode of the circulation well can be switched. By filling different water-containing media, changing the combination of the solid pipe and the screen pipe of the circulation well, and changing the operation mode of the circulation well, the hydraulic circulation characteristics of the groundwater circulation well under different conditions can be characterized.

[0058] Step 3: After the circulation well runs stably, observe the water level change amplitude in each piezometer, and calculate the influence radius of the circulation well by measuring the distance between the two piezometers in the same row where the water level changes significantly and are farthest from the circulation well;

[0059] After the circulation well runs stably, the water level changes in each piezometer tube at different amplitudes. The water level changes in the piezometer tube close to the circulation well is large, while the water level changes in the piezometer tube far away from the circulation well are small or even unchanged. Measure the distance between the two piezometer tubes farthest from the circulation well in the same row where the water level changes significantly. Half of the distance is the influence radius of the circulation well. During the above-mentioned groundwater circulation well simulation repair experiment, the circulation well is opened and the water level values ​​of each piezometer tube are recorded after the water level is basically stable. The influence radius of the circulation well can be calculated.

[0060] Step 4, turning off the circulation pump and turning on the second peristaltic pump to release a supersaturated solution of organic pollutants with a known concentration from the first water inlet of the seepage tank to simulate the migration process of organic pollutants in different aqueous media;

[0061] After the circulation pump is turned off and the groundwater flow rate is stabilized, the second peristaltic pump is turned on to release a supersaturated solution of organic pollutants of known concentration into the aqueous medium at a certain rate through the first water inlet of the seepage trough. During the release of pollutants, water samples are taken at regular intervals through the sampling ports distributed on the back of the seepage trough and the concentration of pollutants therein is measured to obtain the migration pattern of the organic matter in the groundwater. By changing the aqueous medium filled in the seepage trough or the type of organic pollutants released, the migration pattern of organic pollutants of different properties in different aqueous media can be obtained; in addition, by changing the flow rate of the first peristaltic pump connected to the first water inlet, the influence of the groundwater flow rate on the migration pattern of pollutants in the aqueous medium can be analyzed.

[0062] Step 5, turn off the second peristaltic pump and measure the concentration of pollutants therein; turn on the circulation pump to start the circulation well, turn on the third peristaltic pump after the circulation well runs stably, and transport the agent to the aqueous medium, then turn off the circulation pump and the third peristaltic pump, take samples and analyze the concentration of pollutants in the groundwater, and obtain the remediation efficiency of the groundwater circulation well for the organic pollutants.

[0063] After the groundwater pollution has been going on for the expected time, the second peristaltic pump is turned off, and water samples are taken through the sampling port to determine the concentration of pollutants. Then the circulation pump is turned on to start the circulation well. After the circulation well runs stably, the third peristaltic pump is turned on to deliver agents of known concentration at a slow rate, such as redox agents, catalysts, surfactants, etc. After the system has been running for a period of time, the circulation pump and the third peristaltic pump are turned off, and after the groundwater level returns to stability, samples are taken at the sampling port to analyze the concentration of pollutants in the groundwater. By comparing the changing patterns of pollutant concentrations at each sampling port before and after the circulation well is opened, the remediation efficiency of the groundwater circulation well for the organic pollutant can be obtained.

[0064] Before the remediation experiment begins, the forward / reverse circulation mode must be determined based on the properties and distribution characteristics of the pollutants. Light non-aqueous phase liquid (LNAPL) pollutants with a specific gravity less than that of water tend to accumulate in the upper part of the aquifer. At this time, the circulation mode gives priority to reverse circulation, which can prevent the positive circulation from carrying the upper pollutants to the lower part of the aquifer. On the contrary, for heavy non-aqueous phase liquid (DNAPL) pollutants distributed in the lower part of the aquifer, the forward circulation mode is given priority.

[0065] Step 6, conduct a simulation experiment on the expansion of the influence radius of the groundwater circulation well; replace the circulation pump in steps 1 to 3 with a variable frequency pump to adjust the circulation flow rate of groundwater in the water-containing medium; or connect an external high-pressure water gun in steps 1 to 3, and directly apply the high-pressure water generated by the high-pressure water gun to the water-containing medium in the seepage trough to change the porosity or permeability coefficient of the water-containing medium, thereby changing the circulation flow rate of groundwater in the water-containing medium.

[0066] Specifically, by replacing the circulation pump with a variable frequency pump, the influence radius of the circulation well before and after the frequency conversion or before and after the high-pressure water jet is obtained, and the amplification simulation experimental results of the influence radius of the circulation well can be obtained through comparative analysis.

[0067] Example 1

[0068] Step 1, place a circulation well in the center of the seepage trough, and place an injection well 100mm away from the circulation well along the long axis of the seepage trough. The center points of the circulation well and the injection well are on a diameter line. The upper and lower screen tubes of the first circular tube of the circulation well are both 70mm high, the lower solid tube height is 40mm, the middle solid tube height is 380mm, and the upper solid tube height is 140mm; the multiple permeable sieve holes of the second circular tube of the injection well are arranged on the wall of the second circular tube from the bottom of the second circular tube to a height of 550mm. The diameter of the sieve holes of the circulation well and the injection well are both 6mm, and the hole spacing is 8mm. After the positions of the circulation well and the injection well are determined, start filling the seepage trough with homogeneous medium sand with a sieve particle size of 0.25-0.5mm layer by layer to simulate the water-containing medium. The filling height is 550mm, and it is continuously compacted during the filling process.

[0069] Step 2, connect the first water inlet of the seepage trough to the first peristaltic pump so that distilled water is evenly and slowly filled into the water supply compartment, and the flow rate of the first peristaltic pump is 10ml / min. The air in the pores of the water-containing medium is gradually displaced, so that the water-containing medium is completely saturated with water; at this time, the water level in the seepage trough is 550mm. Open the valve of the first water outlet, adjust the valve so that the water level fluctuation amplitude of the water supply compartments on both sides does not exceed 5mm, and at this time, the water level of each pressure measuring tube remains flush, all 550mm. Connect the upper end of the first pipeline to the water inlet of the circulation pump, connect the upper end of the second pipeline to the water outlet of the circulation pump, turn on the circulation pump to start the positive circulation of the groundwater circulation well, and set the flow rate of the circulation pump to 30ml / min. When the circulation well is running stably, the soil non-adsorbent sodium fluorescein tracer solution is added along the long axis of the seepage trough through a long needle tube, the distance between two adjacent addition points is 100mm, and the addition depth is 50mm from the top of the water-containing medium. Through the trajectory of the sodium fluorescein tracer, the elliptical flow field formed by groundwater around the circulation well can be observed with the naked eye.

[0070] Step 3, after the circulation well runs stably, the water level changes in each piezometer tube at different amplitudes, among which the water level changes in the 5th and 6th columns of piezometer tubes close to the circulation well are relatively large. The maximum water level rise height of the piezometer tubes in the 5th column and the 1st row is 45mm, and the maximum water level drop height of the piezometer tubes in the 5th column and the 5th row is 73mm; the water level of the piezometer tubes in the 3rd column and the 1st row rises to 10mm, and the water level of the piezometer tubes in the 3rd column and the 5th row drops to 14mm; the water level of the piezometer tubes in the 8th column and the 1st row rises to 8mm, and the water level of the piezometer tubes in the 5th row drops to 11mm; while the water levels of the piezometer tubes in the 1st, 2nd, 9th and 10th columns far away from the circulation well basically do not change. According to the 1 / 2 of the distance between the two pressure measuring tubes in the same row with obvious water level changes and farthest from the circulation well as the influence radius of the circulation well, it can be calculated that under the experimental conditions of groundwater flow rate of 10ml / min, circulation well flow of 30ml / min, upper and lower screen pipe heights of the circulation well of 70mm, and the distance between the two screen pipes of 380mm, the influence radius of the circulation well is 250mm.

[0071] Step 4: Turn off the circulation pump, wait until the circulation well stops running, and then turn on the second peristaltic pump to release a supersaturated solution of benzene with a concentration of 1800 mg / L through the first water inlet of the seepage tank. The release rate is synchronized with the groundwater flow rate, both of which are 10 ml / min. The release of pollutants continued for 50 days, and samples were taken at the sampling port every 5 days. The Shimadzu GC-2010 gas chromatograph was used to measure the concentration of benzene in water samples at different sampling ports to analyze the migration law of benzene in groundwater.

[0072] By analyzing the change pattern of benzene concentration over time, it can be seen that benzene migrated horizontally and vertically at the same time after entering the groundwater. In the first 10 days, the concentration of benzene could only be measured within 300 mm from the water inlet. As the release time increased, the concentration of benzene in the sampling ports farther away from the release point gradually increased, indicating that the contaminated area formed by benzene in the groundwater gradually expanded. When the release reached the 40th day, the concentration of benzene could be measured in the water samples taken from all sampling ports, and the pollution had basically covered the entire seepage trough. When the pollution lasted for 50 days, the highest concentration of benzene in all water samples was 99.5 mg / L, and the average concentration was 45.03 mg / L.

[0073] Step 5, after the groundwater pollution reaches the 50th day, turn off the second peristaltic pump. Since the density of benzene is smaller than that of water, it belongs to light non-aqueous phase fluid (LNAPL). Connect the water inlet of the circulation pump to the upper end of the second pipe, and the water outlet to the upper end of the first pipe. Turn on the circulation pump, and adjust the operation mode of the circulation well to reverse circulation. After the circulation well runs stably, turn on the third peristaltic pump, set the flow rate to 5ml / min, and deliver a potassium permanganate KMnO4 solution with a concentration of 500mg / L to the water-containing medium, and start timing. Stop the operation of the circulation well and the injection well every 1h, and take water samples from the sampling port to measure the pollutant concentration. With the extension of the reaction time, the pollutant concentration in each sampling port gradually decreases. After the cumulative reaction of 9h, benzene can no longer be detected in most water samples. Only at the bottom of the seepage tank and the individual sampling ports farthest from the circulation well, benzene with a concentration of 3mg / L can be detected, indicating that the pollutants are fully and effectively degraded, and the degradation rate can reach 93.34~100%.

[0074] Step 6, replace the circulation pump in steps 1 to 3 with a variable frequency pump with adjustable frequency. First, set the frequency of the variable frequency pump to 25 Hz, the circulation flow rate at this frequency is 30 ml / min, and the flow rate of the first peristaltic pump is set to 10 ml / min. Under the experimental conditions that the height of the upper and lower sieve tubes of the circulation well is 70 mm and the distance between the two sieve tubes is 380 mm, the influence radius of the circulation well is measured to be 250 mm.

[0075] Then, the flow rate of the first peristaltic pump was maintained at 10 ml / min, and the frequency of the variable frequency pump was increased to 40 Hz. The circulation flow rate at this frequency was 70 ml / min. Under the experimental conditions that the heights of the upper and lower screens of the circulation well were both 70 mm and the distance between the two screens was 380 mm, the influence radius of the circulation well was measured to be 350 mm.

[0076] In step 1 to step 3, an external high-pressure water gun is connected. After the water pressure at the outlet is stable, the pressure is measured to be 50 bar, and the ejected high-pressure water is directly applied to the water-containing medium. The nozzle of the high-pressure water gun is in contact with the top surface of the water-containing medium, and one point is applied every 100 mm along the long axis of the seepage groove, and the action time at each point is 10 minutes. Then, under the experimental conditions of groundwater flow rate of 10 ml / min, circulation well flow of 30 ml / min, upper and lower screen pipe heights of the circulation well of 70 mm, and the distance between the two screen pipes of 380 mm, the influence radius of the circulation well under the experimental conditions is measured to be 350 mm.

[0077] By comparing the influence radius of the circulation well before and after frequency conversion speed regulation, and before and after the high-pressure jet action, it can be seen that under the same other experimental conditions, the influence radius of the circulation well is expanded from 250mm to 350mm.

[0078] The present invention can accurately simulate the restoration experiments of groundwater circulation wells under a variety of different conditions. The experimental device has diverse functions and can comprehensively and accurately simulate the dynamic restoration process of groundwater circulation wells for organic pollutants, accurately monitor and expand the influence radius of groundwater circulation wells, and can provide a theoretical basis and technical support for the research and promotion and application of groundwater circulation well restoration technology.

[0079] Although the present invention has been described in detail in general terms and in specific embodiments in this specification, it is obvious to those skilled in the art that some modifications or improvements may be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A dynamic simulation experimental system for groundwater circulation wells, characterized in that: It comprises a seepage trough (1), a base (2), a circulation well (3) and a drug injection well (4); The seepage trough (1) comprises a rectangular shell (11) with an upper opening and a water-containing medium (12) arranged in the shell; a first water outlet (13) is arranged at the upper end of the right wall of the shell, a first water inlet (14) is arranged at the lower end of the left wall of the shell, and a first drain outlet (15) is arranged at the bottom of the shell near the first water inlet; a first baffle (16) is vertically arranged in the shell near the first water outlet, and a second baffle (17) is vertically arranged in the shell near the first water inlet, wherein a plurality of holes are respectively arranged on the first baffle and the second baffle, and the lower ends of the first baffle (16) and the second baffle (17) are respectively fixedly connected to the upper surface of the bottom wall of the shell, and the front and rear sides of the first baffle (16) and the second baffle (17) are respectively fixed to the front wall and the rear wall of the shell. The first baffle (16) and the second baffle (17) are connected, the height of the first baffle (16) and the second baffle (17) are flush with the first water inlet, and a water supply compartment is formed between the first baffle and the right wall of the shell and between the second baffle and the left wall of the shell respectively; a plurality of second water outlets (18) are arranged on the front wall of the shell (11) between the first baffle (16) and the second baffle (17); a plurality of sampling ports (19) are arranged on the rear wall of the shell (11) between the first baffle (16) and the second baffle (17), and the sampling ports are provided with sampling pipes, and valves are arranged on the sampling pipes; and a first peristaltic pump for adding water and a second peristaltic pump for adding pollutants are also included, and the first water inlet (14) is connected to the water outlets of the first peristaltic pump and the second peristaltic pump respectively through connecting pipes; The base (2) is arranged at the bottom of the shell (11), and the lower surface of the bottom wall of the shell (11) is fixedly connected to the upper surface of the base (2); a pressure measuring plate (21) is also arranged on the upper surface of the base (2), and a plurality of pressure measuring tubes (22) are arranged vertically on the pressure measuring plate; the plurality of second water outlets (18) are respectively connected to the lower ends of the plurality of pressure measuring tubes through pipelines; The circulation well (3) comprises a first circular pipe (31) vertically arranged on the bottom surface of the seepage groove (1), the top of the first circular pipe is provided with a top cover, and the bottom is closed; the first circular pipe (31) is connected from bottom to top by a lower solid pipe (35), a lower screen pipe (36), a middle solid pipe (37), an upper screen pipe (38) and an upper solid pipe (39); the walls of the lower solid pipe, the middle solid pipe and the upper solid pipe are impermeable, and the walls of the lower screen pipe and the upper screen pipe are provided with a plurality of water permeable holes; a water-impermeable transverse partition (32) is horizontally arranged in the middle of the middle solid pipe (37) A coaxial first pipe (33) is arranged at the center of the first circular tube, the lower end of the first pipe (33) passes through the top cover and the transverse partition (32) in sequence and extends downward to the lower screen tube (36); a second pipe (34) is also included, the lower end of the second pipe (34) passes through the top cover and extends downward to the upper screen tube (38); a circulating pump is also included, the upper end of the first pipe (33) is connected to the water inlet of the circulating pump; the upper end of the second pipe (34) is connected to the water outlet of the circulating pump; The injection well (4) comprises a second circular tube (41); the second circular tube (41) is vertically arranged on one side of the first circular tube (31) in the seepage trough (1); the bottom of the second circular tube (41) is closed; a plurality of water-permeable sieve holes (42) are arranged on the wall of the second circular tube; the second circular tube further comprises a dosing tube (43) and a third peristaltic pump; the head end of the dosing tube is connected to the output end of the third peristaltic pump; the tail end of the dosing tube extends into the second circular tube.

2. The dynamic simulation experimental system of groundwater circulation well according to claim 1 is characterized in that: The number of the second water outlets (18) is 50, which are evenly arranged in 5 rows from top to bottom, and each row of second water outlets (18) has 10 evenly arranged from left to right, and the distance between two adjacent second water outlets (18) is 100 mm.

3. The dynamic simulation experimental system of groundwater circulation well according to claim 1 is characterized in that: The number of the pressure measuring tubes (22) is 50.

4. The dynamic simulation experimental system of groundwater circulation well according to claim 1 is characterized in that: The number of the sampling ports (19) is 50, which are evenly arranged in 5 rows from top to bottom, with 10 sampling ports evenly arranged in each row from left to right, and the distance between two adjacent sampling ports is 100 mm.

5. The dynamic simulation experimental system of groundwater circulation well according to claim 1 is characterized in that: The base is a stainless steel bracket, and a sliding wheel is arranged on the outer side of the lower surface of the stainless steel bracket.

6. The dynamic simulation experimental system of groundwater circulation well according to claim 1, characterized in that: A stainless steel screen or a nylon screen is respectively arranged on the right side of the first baffle and the left side of the second baffle.

7. The dynamic simulation experimental system of groundwater circulation well according to claim 1 is characterized in that: The outer side walls of the first circular tube (31) and the second circular tube (41) are respectively provided with a stainless steel screen or a nylon screen.

8. The dynamic simulation experimental system of groundwater circulation well according to claim 1, characterized in that: The water-containing medium (12) includes any one or more of coarse sand, medium sand, fine sand, silt sand or clay.

9. A dynamic simulation experimental method for groundwater circulation wells, characterized in that: The following steps are involved: Step 1, placing a circulation well and a drug injection well in the seepage trough, and then filling the seepage trough with water-containing medium; Step 2, start the first peristaltic pump to pass water into the seepage tank to simulate groundwater, start the circulation pump to start the circulation well after the water-containing medium is saturated with water, add an equal amount of tracer every 100 mm in the horizontal direction at 50 mm below the upper surface of the water-containing medium, and trace the hydraulic circulation characteristics of the groundwater in the circulation well; Step 3: After the circulation well runs stably, observe the water level change amplitude in each piezometer, and calculate the influence radius of the circulation well by measuring the distance between the two piezometers in the same row where the water level changes significantly and are farthest from the circulation well; Step 4, turning off the circulation pump and turning on the second peristaltic pump to release a supersaturated solution of organic pollutants with a known concentration from the first water inlet of the seepage tank to simulate the migration process of organic pollutants in different aqueous media; Step 5, turn off the second peristaltic pump, take samples to determine the concentration of pollutants in the groundwater; turn on the circulation pump to start the circulation well, turn on the third peristaltic pump after the circulation well runs stably, and transport the agent to the aqueous medium. Then turn off the circulation pump and the third peristaltic pump, take samples to analyze the concentration of pollutants in the groundwater, and obtain the remediation efficiency of the groundwater circulation well for the organic pollutants.

10. A dynamic simulation experimental method for groundwater circulation well according to claim 9, characterized in that: The method also includes step 6, replacing the circulation pump in steps 1 to 3 with a variable frequency pump to adjust the circulation flow rate of groundwater in the water-containing medium; or connecting an external high-pressure water gun in steps 1 to 3, and directly applying the high-pressure water generated by the high-pressure water gun to the water-containing medium in the seepage trough to change the porosity or permeability coefficient of the water-containing medium, and conducting a simulation experiment on the expansion of the influence radius of the groundwater circulation well.

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