In-situ treatment system and treatment method for groundwater pollution

Abstract

The present invention discloses an in-situ treatment system for groundwater pollution and its treatment method, belonging to the technical field of groundwater remediation. The treatment system includes an outer well pipe of a circulation well, an inner well pipe of the circulation well, an anode combination device arranged on the outer wall of the inner well pipe of the circulation well, a reference electrode combination device arranged on the outer wall of the inner well pipe of the circulation well, an aeration head arranged in the inner well pipe of the circulation well, an activated carbon electrode box arranged on the inner well pipe of the circulation well, a gas flow meter arranged on the ground, an air compressor arranged on the ground, an integrated activated carbon adsorption box arranged on the ground, and a potentiostat arranged on the ground. By designing different electrodes and adding ferrous sulfate heptahydrate, an electro-Fenton reaction is formed in the well, and strongly oxidizing hydroxyl radicals are generated by the reaction, thereby degrading organic pollution. By setting the well body as the cathode and applying an external current for cathodic protection, the service life of the iron circulation well is extended.

Description

Technical Field

[0001] The present invention belongs to the field of groundwater remediation, and particularly relates to an in-situ treatment system for groundwater pollution and a treatment method thereof. Background Art

[0002] Groundwater is one of the commonly used water sources for humans. Groundwater resources are an important part of water resources. However, groundwater pollution occurs frequently. For example, wastewater discharge, industrial waste residues, agricultural irrigation, landfill leakage, and damage to transportation pipelines and storage tanks of petrochemical raw materials may all cause groundwater pollution. Whether these water sources are used for drinking or other purposes, they will seriously affect our physical health. The development of groundwater pollution control and remediation work is of great significance for the sustainable utilization of groundwater resources.

[0003] At present, relatively mature technological means have been developed for groundwater remediation. Well-known groundwater remediation technologies include extraction technology, air stripping technology, air sparging technology, bioremediation technology, permeable reactive barrier technology, in-situ chemical remediation, etc., which have been applied in various fields. During the use process, people have gradually discovered some deficiencies of these technologies. For example, in actual project applications, due to the influence of the use environment, traditional iron circulation wells are prone to rust, resulting in the circulation wells not reaching the designed service life. Therefore, there is an urgent need to develop a new in-situ treatment system for groundwater pollution that can extend the service life of traditional iron circulation wells. Summary of the Invention

[0004] The present invention provides an in-situ treatment system for groundwater pollution and a treatment method thereof, which can effectively solve the problems raised in the above background art.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] Compared with the prior art, the beneficial effects of the present invention are as follows: By designing different electrodes and adding ferrous sulfate heptahydrate, an electro-Fenton reaction is formed in the well, and strongly oxidizing hydroxyl radicals are generated by the reaction, thereby degrading organic pollution. The aeration head is powered by an air compressor to lift the polluted water from the bottom of the inner well pipe to the upper perforated holes of the outer well pipe. At the same time, the volatile pollutants in the polluted water are stripped into the air, and the polluted water is converted into clean water rich in oxygen. The clean water rich in oxygen flows out of the upper perforated holes of the outer well pipe and circulates outside the well, and the polluted water flows into the circulation well from the lower perforated holes of the outer well pipe, forming a hydraulic circulation inside and outside the circulation well. By setting the well body as the cathode and applying an external current for cathodic protection, the service life of the iron circulation well is extended.

[0007] Compared with the prior art, the working principle of the present invention is as follows: Due to the particularity of the iron circulation well, the well pipe can be protected from rust and corrosion by the cathodic protection method with an external current.

[0008] According to the appropriate design of the circular well structure, a potentiostat and an anode are set, and the circular well and the activated carbon electrode box are used as the cathode. The impressed current cathodic protection method for cathodic protection of the circular well casing is realized. Through the activated carbon electrode box arranged in the inner well casing, the current, voltage, and aeration volume are adjusted, and ferrous sulfate heptahydrate (FeSO 4 ·7H 2 O) is added to achieve electro-Fenton in the circular well. The carbon material has a relatively high redox potential and low catalytic activity for the decomposition of H 2 O 2 . This unique property is conducive to the reduction of oxygen (O 2 ) to hydrogen peroxide through electrochemical reactions. The aeration head aerates in the inner well casing, continuously providing dissolved oxygen and upward driving force for the wastewater. The wastewater rich in dissolved oxygen contacts the activated carbon electrode during the upward process, and a reduction reaction occurs at the cathode, reacting oxygen to generate hydrogen peroxide and reacting with Fe 2+ in the added ferrous sulfate heptahydrate to undergo the Fenton reaction, generating the strong oxidizing substance hydroxyl radical (·OH). The reaction formulas are as follows:

[0009] O 2 +2H + +2e-→H 2 O 2 (Equation 1.1);

[0010] Fe 2+ +H 2 O 2 +H+→Fe 3+ +H 2 O+·OH (Equation 1.2);

[0011] ·OH+RH→R·+H 2 O (Equation 1.3);

[0012] Fe 3+ +e-→Fe 2+ (Equation 1.4);

[0013] The magnitude of the current density not only determines the treatment cost but also directly affects the generation efficiency of H 2 O 2 near the cathode and the generation efficiency of Fe 2+ , thus affecting the Fenton reaction process. The reaction formulas are as follows:

[0014] O 2 +2H + +2e-→H 2 O 2 (Equation 1.1);

[0015] Fe 3+ +e-→Fe2+ (Equation 1.4);

[0016] Fe 2+ +H 2 O 2 →Fe 3+ +OH - +·OH (Equation 1.5);

[0017] The anode rod is consumed due to the length of service time, resulting in a significant increase in the anode grounding resistance and inability to continue normal operation due to mismatch with the output of the power supply equipment. The quality of the anode rod should be designed according to relevant specifications and design service life. The total mass G of the anode can be calculated by the following formula t (kg):

[0018]

[0019] Where: T—the design life of the anode, a;

[0020] g—the consumption rate of the anode, kg / A*a;

[0021] I—the working current of the anode, A;

[0022] K—the utilization coefficient of the anode, usually taken as 0.7 - 0.85.

[0023] This patent uses a high-silicon cast iron anode, and its anode design current density is 5A / m 2 ~80A / m 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0025] Figure 1 Shows an overall schematic diagram of an in-situ groundwater pollution treatment system;

[0026] Figure 2 Shows a schematic diagram of the installation position of the electrode device;

[0027] Figure 3 Shows a schematic diagram of the installation of the electrode combination device;

[0028] Figure 4 Shows a design schematic diagram of the top view, front cross-sectional view and front perspective view of the insulating flange;

[0029] Figure 5 Shows a design schematic diagram of the top view, front cross-sectional view and front perspective view of the insulating electrode support;

[0030] Figure 6Shows the top view, front view cross-section and front view perspective design schematic diagram of the ring brush;

[0031] Figure 7 Shows the cross-sectional view of the integrated activated carbon adsorption box;

[0032] Figure 8 Shows the structural diagram of an activated carbon electrode box;

[0033] Reference numerals in the figure: 1. Potentiostat; 2. Anode power line; 3. Cathode power line; 4. Reference electrode power line; 5. Gas pipeline; 6. Gas flow meter; 7. Air compressor; 8. Tail gas pipe; 9. Integrated activated carbon adsorption box; 10. Upper perforated hole of the circulation well; 11. Ring seal; 12. Inner well pipe of the circulation well; 13. Outer well pipe of the circulation well; 14. Bracket; 15. Anode assembly; 15a. Anode rod; 16. Aeration head; 17. Lower perforated hole of the circulation well; 18. Reference electrode assembly; 18a. Reference electrode rod; 19. Activated carbon electrode box; 20. Steel cable; 21. Screw; 22. Insulating flange; 23. Insulating electrode bracket; 24. Ring brush; 25. Screw opening; 26. Electrode rod slot; 27. Brush; 28. Rubber pad; 29. Activated carbon drawer; 30. Air inlet; 31. Side sealing guide rail; 32. Activated carbon; 33. Bottom sealing strip; 34. Exhaust fan; 35. Air outlet. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] Figure 1 Shows the overall schematic diagram of an in-situ groundwater pollution treatment system, including the outer well pipe 13 of the circulation well, the ring seal 11 arranged on the outer well pipe 13 of the circulation well, the upper perforated hole 10 of the circulation well is opened on the upper part of the outer well pipe 11 of the circulation well, the lower perforated hole 17 of the circulation well is opened on the lower part of the outer well pipe 13 of the circulation well, the ring seal 11 is located below the upper perforated hole 10 of the circulation well, and the ring seal 11 is welded to connect the inner well pipe 12 and the outer well pipe 13 of the circulation well;

[0036] It also includes an anode assembly device 15 arranged on the outer wall of the well pipe 12 in the circulation well, a reference electrode assembly device 18 arranged on the outer wall of the well pipe 12 in the circulation well, an aeration head 16 arranged in the well pipe in the circulation well, an activated carbon electrode box 19 arranged on the well pipe 12 in the circulation well, a gas flow meter 6 arranged on the ground, an air compressor 7 arranged on the ground, an integrated activated carbon adsorption box 9 arranged on the ground, and a potentiostat 1 arranged on the ground; the anode assembly device 15 is connected to the well pipe 12 in the circulation well through a bracket 14, the anode assembly device 15 is connected to the potentiostat 1 through an anode power line 2, the reference electrode assembly device 18 is connected to the well pipe 12 in the circulation well through a bracket 14, the reference electrode assembly device 18 is connected to the potentiostat 1 through a reference electrode power line 4, the activated carbon electrode box 19 and the well pipe 12 in the circulation well are connected to the potentiostat 1 through a cathode power line 3, and the activated carbon electrode box 19 is suspended in the well pipe 12 in the circulation well through a steel cable 20; the aeration head 16 is connected to the gas flow meter 6 through an air delivery pipe 5, the gas flow meter 6 is connected to the air compressor 7 through an air delivery pipe 5, an exhaust gas outlet is opened at the upper part of the outer well pipe 13 of the circulation well, and the exhaust gas outlet is connected to the integrated activated carbon adsorption box 9 through an exhaust gas pipe 8.

[0037] Figure 2 The schematic diagram showing the installation position of the electrode device includes the inner well pipe 12 in the circulation well, the outer well pipe 13 in the circulation well, the anode assembly device 15 and the reference electrode assembly device 18 are installed on both sides of the inner well pipe 12 in the circulation well, and the anode assembly device 15 and the reference electrode assembly device 18 are connected to the inner well pipe 12 in the circulation well through a bracket 14.

[0038] Figure 3 The schematic diagram showing the installation of the electrode assembly device includes the inner well pipe 12 in the circulation well, the outer well pipe 12 in the circulation well is connected to the insulating flange 22 through a bracket 14, and the insulating flange 22 and the bracket 14 are fixed by screws 21; it includes an insulating electrode bracket 23, and the insulating electrode bracket 23 is arranged at the upper and lower ends of the anode rod 15a and the reference electrode rod 18a; the insulating electrode bracket 23 is fixed to the insulating flange 22 and the bracket 14 by screws 21; it includes an annular brush 24, and the annular brush 24 is respectively sleeved into the anode rod 15a and the reference electrode rod 18a.

[0039] Figures 4 to 6 The schematic diagram showing the design of each component includes the insulating flange 22, and screw holes 25 are opened on the insulating flange; it includes the insulating electrode bracket 23, screw holes 25 are opened on the insulating electrode bracket 23, and an electric shock rod slot 26 for fixing is opened on the insulating electrode bracket 23; it includes that brush bristles 27 are arranged on the inner ring of the annular brush 24.

[0040] Figure 7Shows a sectional view of an integrated activated carbon adsorption box, including an integrated activated carbon adsorption box 9, an air inlet 30 and an air outlet 35 arranged on both sides of the integrated activated carbon adsorption box 9, side sealing guide rails 31 arranged on both sides of the integrated activated carbon adsorption box 9, and a bottom sealing rubber strip 33 arranged at the bottom of the integrated activated carbon adsorption box 9, including an activated carbon drawer 29, a rubber pad 28 arranged on the activated carbon drawer 29, the activated carbon drawer 29 is designed with a snap fast - disassembly design, and an exhaust fan 34 is arranged at the air outlet 35.

[0041] Figure 8 Shows a structural diagram of an activated carbon electrode box, including an activated carbon electrode box 19 and packing activated carbon 32 arranged inside the activated carbon electrode box 19.

[0042] The treatment method using a groundwater pollution in - situ treatment system of the present application includes the following sequence and steps:

[0043] a. Estimate the positions and depths of the injection wells according to the hydrogeological conditions of the groundwater pollution area, drill well holes through a drilling rig, and the final hole is at the bottom plate of the contaminated groundwater or 20 cm below the deepest part of the pollution.

[0044] b. Design the electrode rods of the anode combination device according to the designed service life.

[0045] c. Turn on the potentiostat, and select the protection voltage and protection current of the anode according to the local hydrogeology.

[0046] d. Add ferrous sulfate heptahydrate, start aeration, seal the wellhead of the injection well, increase the current density of the activated carbon electrode box, carry out the electro - Fenton reaction, and turn on the integrated activated carbon adsorption box for tail gas treatment.

[0047] e. Regularly detect the potential of the potentiostat and the air compressor, and replace the activated carbon in the integrated activated carbon adsorption box.

[0048] Refer to GBT21448 - 2017 Cathodic Protection Technical Code for Buried Steel Pipelines, Cathodic Protection and Anodic Protection: Principles, Technologies and Engineering Applications. In step c, the anodic protection voltage is - 0.8V and the protection current is 5A / m 2 。

[0049] Table 1 below shows the natural potential, minimum protection potential and limiting critical potential of metal materials in soil and water in GBT21448 - 2017.

[0050] Table 1 Natural potential, minimum protection potential and limiting critical potential of metal materials in soil and water

[0051]

[0052] An in-situ treatment system for groundwater pollution, comprising an outer well pipe of a circulation well, an annular seal arranged on the outer well pipe of the circulation well, perforated holes opened at the upper part of the outer well pipe of the circulation well, perforated holes opened at the lower part of the outer well pipe of the circulation well, the annular seal being located below the perforated holes at the upper part of the outer well pipe, the annular seal connecting the inner well pipe of the circulation well and the outer well pipe of the circulation well by welding, an anode assembly arranged on the outer wall of the inner well pipe of the circulation well, a reference electrode assembly arranged on the outer wall of the inner well pipe of the circulation well, an aeration head arranged in the inner well pipe of the circulation well, an activated carbon electrode box arranged on the inner well pipe of the circulation well, a gas flowmeter arranged on the ground, an air compressor arranged on the ground, an integrated activated carbon adsorption box arranged on the ground, and a potentiostat arranged on the ground; the anode assembly is connected to the inner well pipe of the circulation well through a bracket, the anode assembly is connected to the potentiostat through an anode power line, the reference electrode assembly is connected to the inner well pipe of the circulation well through a bracket, the reference electrode is connected to the potentiostat through a reference electrode power line, the activated carbon electrode box is connected to the potentiostat through a cathode power line, the activated carbon electrode box is suspended in the inner well pipe of the circulation well by a steel cable, and the cathode power line is connected to the inner well pipe of the circulation well; the aeration head is connected to the gas flowmeter through an air delivery pipe, the gas flowmeter is connected to the air compressor through an air delivery pipe, a tail gas outlet is opened at the upper part of the outer well pipe of the circulation well, and the tail gas outlet is connected to the integrated activated carbon adsorption box through a tail gas pipe.

[0053] The inner diameter of the outer well pipe of the circulation well is 40 - 50 cm; a perforated section is provided at the lower part of the outer well pipe of the circulation well, with a perforated length of 30 - 40 cm; a perforated section is provided at the upper part of the outer well pipe of the circulation well, with a perforated length of 30 - 40 cm. The inner diameter of the inner well pipe of the circulation well is 20 - 30 cm; the activated carbon electrode box is in the shape of a hollow cylinder, the inner diameter of its inner ring should not be less than 10 cm, and its length should be designed according to the actual site, and the installation position should be near the aeration head. The activated carbon electrode box is fixed by a steel cable; the anode assembly device includes an insulating flange, a ring-shaped brush, an insulating electrode bracket, screws, and an anode rod. The insulating flange is connected to the bracket by screws. The ring-shaped brush is arranged on the anode rod, and the ring-shaped brush floats up and down with the water flow to brush off the deposits on the anode rod. The ring-shaped brush should be designed according to the actual size of the anode rod. The insulating electrode bracket is arranged at both upper and lower ends of the electrode rod and serves to fix the anode rod. The insulating electrode bracket is connected to the insulating flange by screws; the reference electrode assembly device includes an insulating flange, a ring-shaped brush, an insulating electrode bracket, screws, and a reference electrode rod. The insulating flange is connected to the bracket by screws. The ring-shaped brush is arranged on the reference electrode rod, and the ring-shaped brush floats up and down with the water flow to brush off the deposits on the reference electrode rod. The ring-shaped brush should be designed according to the actual size of the reference electrode rod. The insulating electrode bracket is arranged at both upper and lower ends of the reference electrode rod and serves to fix the reference electrode rod. The insulating electrode bracket is connected to the insulating flange by screws; the integrated activated carbon adsorption box includes an air inlet provided at the front end of the adsorption box, a side sealing guide rail provided at the side of the box body, a bottom sealing rubber strip provided at the bottom of the box body, three activated carbon drawers provided above the box body, a rubber pad provided between the activated carbon drawer and the box body, an exhaust fan provided at the rear end of the box body, and an air outlet provided at the rear end of the box body; the activated carbon drawer is provided with a snap-fastening and quick-release design for convenient and quick replacement of the activated carbon. The rubber pad has a sealing function. The side sealing guide rail has the function of facilitating installation and disassembly and preventing gas from flowing through between the integrated activated carbon adsorption box and the activated carbon drawer. The exhaust fan extracts the tail gas to reduce the working pressure of the air compressor.

[0054] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0055] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An in-situ treatment system for groundwater pollution, characterized in that, the treatment system includes an outer well pipe and an inner well pipe of a circulation well, an annular seal disposed between the outer well pipe and the inner well pipe of the circulation well, a gas flow meter disposed on the ground, an air compressor disposed on the ground, an integrated activated carbon adsorption box disposed on the ground, and a potentiostat disposed on the ground; the upper part of the outer well pipe of the circulation well is provided with upper perforated holes of the circulation well, the lower part of the outer well pipe of the circulation well is provided with lower perforated holes of the circulation well, the annular seal is located below the upper perforated holes of the circulation well, an anode assembly and a reference electrode assembly are disposed on the outer wall of the inner well pipe of the circulation well, and an aeration head and an activated carbon electrode box are disposed in the inner well pipe of the circulation well; the anode assembly is connected to the potentiostat through an anode power line, the reference electrode assembly is connected to the potentiostat through a reference electrode power line, and the activated carbon electrode box and the inner well pipe of the circulation well are connected to the potentiostat through a cathode power line; the aeration head is connected to the gas flow meter through an air delivery pipe, and the gas flow meter is connected to the air compressor through an air delivery pipe; the upper part of the outer well pipe of the circulation well is provided with a tail gas outlet, and the tail gas outlet is connected to the integrated activated carbon adsorption box through a tail gas pipe; the activated carbon electrode box is installed near the aeration head; the anode assembly and the reference electrode assembly are connected to the inner well pipe of the circulation well through brackets; the activated carbon electrode box is suspended in the inner well pipe of the circulation well by a steel cable; the anode assembly includes an insulating flange, an insulating electrode bracket, and an anode rod. The insulating flange is provided with an electrode rod slot in the middle for fixing the anode rod. The reference electrode assembly includes an insulating flange, an insulating electrode bracket, and a reference electrode rod. The insulating flange is provided with an electrode rod slot in the middle for fixing the reference electrode rod. The insulating flange is fixedly connected to the insulating electrode bracket by screws.

2. An in-situ treatment system for groundwater pollution according to claim 1, characterized in that: the annular seal connects the inner well pipe and the outer well pipe of the circulation well by welding.

3. An in-situ treatment system for groundwater pollution according to claim 1, characterized in that: a ring-shaped brush is sleeved on the outer wall of the anode rod, and a ring-shaped brush is sleeved on the outer wall of the reference electrode rod.

4. An in-situ treatment system for groundwater pollution according to claim 1, characterized in that: the integrated activated carbon adsorption box includes an activated carbon drawer. A rubber pad is provided on the top of the activated carbon drawer. Side sealing rails are provided at the side joints of the integrated activated carbon adsorption box, a bottom sealing strip is provided at the bottom joint, an air inlet and an air outlet are respectively provided on both sides thereof. The air inlet is communicated with the tail gas pipe, and a suction fan is provided at the air outlet.

5. A treatment method for an in-situ treatment system for groundwater pollution according to any one of claims 1 to 4, characterized in that, it includes the following steps: a. Estimate the well location and depth of the circulation well according to the hydrogeological conditions of the groundwater pollution area, drill a well hole with a drilling rig, and the final hole is at the bottom plate of the contaminated groundwater or 20 cm below the deepest part of the pollution; b. Design the electrode rods of the anode combination device according to the designed service life; c. Turn on the potentiostat, and select the protection voltage and protection current of the anode according to the local hydrogeology; d. Add ferrous sulfate heptahydrate, start aeration, seal the wellhead of the circulation well, increase the current density of the activated carbon electrode box, carry out the electro-Fenton reaction, and turn on the integrated activated carbon adsorption box for tail gas treatment; e. Regularly detect the potential of the potentiostat and the air compressor, and replace the activated carbon in the integrated activated carbon adsorption box.

6. The treatment method of an in-situ groundwater pollution treatment system according to claim 5, characterized in that, The protection voltage of the anode is -0.8V, and the protection current is 5A / m 2 .

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