A source treatment system and method for acidic wastewater from abandoned pyrite mine adits

Abstract

The present application relates to the technical field of abandoned pyrite mine management, and particularly relates to a system and method for treating acid waste water at the source of abandoned pyrite mine adit, comprising an acid waste water in-situ treatment device, a flow guide device, a seepage prevention structure arranged on the surface of residual waste rock at the bottom of the adit, a grouting reinforcement water stop structure arranged around the over-standard gushing water point and the seepage point, and a surface sealing seepage prevention layer arranged around the exposed surface of the broken rock mass, the over-standard gushing water point and the seepage point; the acid waste water in-situ treatment device is arranged at the adit opening, and is used for collecting and treating acid waste water; one end of the flow guide device is located below the over-standard gushing water point and the seepage point, and the other end extends to the outside of the adit, and is used for guiding the unpolluted gushing water and seepage water to the outside of the adit for discharge. The present application can better solve the problem of continuous gushing water in the pyrite mine adit in the region with complex geological conditions by in-situ treatment of the adit of the abandoned pyrite mine, including hole wall seepage prevention, clear water dredging, waste rock storage and waste water treatment.

Description

Technical Field

[0001] This invention relates to the field of abandoned pyrite mine treatment technology, specifically to a source treatment system and method for acidic wastewater from abandoned pyrite mine adits. Background Technology

[0002] Currently, the treatment of abandoned pyrite mine adits mainly involves simple backfilling and sealing. This method is effective and quick for mines without water accumulation or inflow, but it fails to control pollution at its source. In actual projects, there are many problems with the re-spread of acidic wastewater and pollution. In particular, for mines with continuous water inflow, the pH value of the water is low and the volume is large. If not properly treated, it will cause serious ecological and environmental problems. Moreover, pyrite mines with continuous water inflow are often located in areas with developed karst, complex geological conditions, and poor mountain stability. The geological conditions of the mines in these areas are unclear, exploration is difficult, construction is dangerous, and there are major water inflow points and multiple small seepage points. Entering the mine for construction without proper knowledge poses significant safety hazards. There is currently a lack of a site-specific approach to managing this type of mine, and dealing with the acidic wastewater gushing out of the mine is also a major challenge. In addition to the possibility of causing diffuse pollution, the backfilling and sealing process also carries the risk of causing instability of the nearby mountains due to the continuous rise of water head in the mine roof and the resulting high water pressure. Summary of the Invention

[0003] The purpose of this invention is to provide a source treatment system and method for acidic wastewater from abandoned pyrite mine adits, which can reduce water volume at the source, prevent the spread of acidic wastewater pollution, and achieve the goal of comprehensive treatment and source control of acidic wastewater through in-situ multi-stage treatment.

[0004] To achieve the above objectives, the technical solution of the present invention is a source treatment system for acidic wastewater from an abandoned pyrite mine adit, comprising an in-situ acidic wastewater treatment device, a diversion device, an anti-seepage structure installed on the surface of the waste rock residue at the bottom of the adit, a grouting reinforcement and water-stopping structure installed around the excessive water inflow points and seepage points, and a surface sealing anti-seepage layer installed on the exposed surface of the fractured rock mass and around the non-excessive water inflow points and seepage points; the in-situ acidic wastewater treatment device is installed at the adit entrance to collect and treat the acidic wastewater formed by the excessive water inflow points and seepage points; one end of the diversion device is located below the non-excessive water inflow points and seepage points, and the other end extends outside the adit to divert the uncontaminated water inflow and seepage to the outside of the adit for discharge.

[0005] As one implementation method, the surface sealing impermeable layer is made of plain concrete spraying, and 5 kg of cement-based penetrating crystalline waterproof material and 15% to 25% fly ash are added to each cubic meter of concrete.

[0006] As one implementation method, the grouting reinforcement and water-stopping structure is formed by injecting high sulfate-resistant cement grout into the surrounding rock through multi-layer grouting pipes set around the excessive water inflow point and seepage point.

[0007] As one embodiment, the in-situ treatment device for acidic wastewater includes a buffer tank, a reduction tank, a neutralization tank, and a sedimentation tank that are connected sequentially along the flow direction of the acidic wastewater.

[0008] As one embodiment, a hydrogen sulfide gas collection hood is provided at the top of the reduction tank. The hydrogen sulfide gas collection hood is connected to the sedimentation tank through a first pipe, and the end of the first pipe is located below the liquid surface of the sedimentation tank.

[0009] As one embodiment, the seepage-proof structure includes a passivation layer formed on the surface of the residual waste rock and a seepage-proof covering layer disposed on the surface of the passivation layer. The passivation layer is formed by mixing the surface waste rock and calcium oxide.

[0010] As one embodiment, a carbon dioxide gas collection hood is provided on the top of the neutralization tank, and a gas distribution pipe is provided inside the passivation layer. The carbon dioxide gas collection hood is connected to the gas distribution pipe through a second pipe.

[0011] As one implementation method, the hydrogen sulfide gas collection hood is also connected to the gas distribution pipe via a third pipe.

[0012] As one implementation method, there are at least two acidic wastewater in-situ treatment devices connected in parallel, which completely cover the overflow range of the acidic wastewater.

[0013] This invention also provides a method for treating acidic wastewater from abandoned pyrite mine adits, comprising the following steps:

[0014] First, investigate the exposed surface of the fractured rock mass, water inflow points, and seepage points inside the adit of the abandoned pyrite mine. Investigate, sample, and test the main water inflow points and seepage points on the bedrock surface inside the tunnel to determine the extent of pollution.

[0015] Then, based on the exploration and testing results, the acidic wastewater source treatment system described above for abandoned pyrite mine adits is implemented in the adits. This isolates the exposed surface of the fractured rock mass and the waste rock residue at the bottom of the adits from the water. Uncontaminated gushing and seeping water is diverted to the outside of the tunnel for discharge. The acidic wastewater is collected in an in-situ acidic wastewater treatment device and sequentially enters a buffer tank, a reduction tank, a neutralization tank, and a sedimentation tank. In the reduction zone, sulfates in the acidic wastewater are reduced to hydrogen sulfide by sulfate-reducing bacteria. In the neutralization zone, acidic substances in the acidic wastewater react with limestone to generate carbon dioxide. After hydrogen sulfide is generated in the reduction tank, it is first introduced into the waste rock residue to react with heavy metals in the waste rock residue to generate metal sulfides. Then, carbon dioxide gas generated in the neutralization tank is introduced into the waste rock residue to react with the calcium oxide on the surface of the waste rock residue to generate a calcium-based carbonate passivation layer. Finally, hydrogen sulfide is introduced into the sedimentation tank to react with heavy metals in the wastewater to generate metal sulfide precipitates.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention sets up a grouting reinforcement and water-stopping structure around the excessive water inflow point and seepage point, provides advanced support for the broken rock mass inside the abandoned mine tunnel, and seals the water inflow point and seepage point around the tunnel, thus solving the long-term safety problem of in-situ treatment of historical mine tunnels.

[0018] (2) The present invention adopts the method of dredging instead of blocking, separating clean water from dirty water, identifying uncontaminated water inflow points and seepage points, reinforcing the surface around them, and collecting uncontaminated water inflow points and seepage points through a diversion device and then diverting it to the outside of the tunnel, thereby reducing the possibility of clean water coming into contact with waste rock and broken rock exposed surfaces from the source and reducing the amount of acidic wastewater generated.

[0019] (3) The present invention sets an anti-seepage structure on the surface of the waste rock residue left at the bottom of the adit, so as to completely isolate the wastewater and the waste rock residue left in the tunnel and avoid the pollution from continuing to worsen;

[0020] (4) The present invention adapts to local conditions and sets up an in-situ treatment device for acidic wastewater at the entrance of the tunnel to achieve in-situ treatment of the converging acidic wastewater. This not only enables the source control of acidic wastewater and avoids further spread of pollutants, but also solves the problems of land acquisition and site selection that are often encountered in engineering.

[0021] (5) In this invention, after acidic wastewater enters the acidic wastewater in-situ treatment device, it passes through a buffer tank, a reduction tank, a neutralization tank and a sedimentation tank in sequence. The pH of the wastewater increases and the acidity decreases. Multiple pollutants such as sulfate and heavy metals are reduced and controlled, which can achieve source control of acidic wastewater.

[0022] (6) This invention utilizes hydrogen sulfide generated in the reduction tank to enhance the treatment of heavy metals in waste rock slag and effluent, and utilizes carbon dioxide generated in the neutralization tank to enhance the passivation effect of waste rock slag, thereby achieving waste treatment with waste.

[0023] (7) The organic matter reduction layer of the reduction tank and the neutralization layer of the neutralization tank of the present invention are both modularly designed, which enables convenient and quick installation, cleaning and replacement, and greatly improves work efficiency. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of the source treatment system for acidic wastewater from abandoned pyrite mine adits provided in an embodiment of the present invention;

[0026] In the diagram: 1. Waste rock slag; 2. Passivation layer; 3. Impermeable covering layer; 4. Gas distribution pipe; 5. Flow guiding device; 6. Grouting pipe; 7. Buffer pool; 8. Reduction pool; 9. Neutralization pool; 10. Sedimentation pool; 11. Hydrogen sulfide gas collection hood; 12. Carbon dioxide gas collection hood. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0029] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more, and "a number" means at least one.

[0030] Example 1

[0031] like Figure 1 As shown, a source treatment system for acidic wastewater from an abandoned pyrite mine adit includes an in-situ acidic wastewater treatment device, a diversion device 5, an anti-seepage structure installed on the surface of the waste rock residue 1 at the bottom of the adit, a grouting reinforcement and water-stopping structure installed around the excessive water inflow points and seepage points, and a surface sealing anti-seepage layer installed on the exposed surface of the fractured rock mass and around the non-excessive water inflow points and seepage points. The in-situ acidic wastewater treatment device is installed at the adit entrance to collect and treat the acidic wastewater formed by the excessive water inflow points and seepage points. One end of the diversion device 5 is located below the non-excessive water inflow points and seepage points, and the other end extends outside the adit to divert the uncontaminated water inflow and seepage to the outside of the adit for discharge.

[0032] During the mining process of pyrite mines, a large amount of waste rock slag 1 is generated, which is usually piled at the bottom of the adit. This waste rock slag contains a large amount of FeS2 in the exposed surface of the fractured rock mass of the pyrite mine. When it comes into contact with water, it will form acidic wastewater with high content of heavy metals such as iron and manganese and sulfates under the combined action of air and bacteria. In order to prevent the adit water and seepage from coming into contact with the exposed surface of the fractured rock mass and these waste rock slag 1 to form acidic wastewater, this embodiment covers the exposed surface of the fractured rock mass with a surface-sealed impermeable layer. A passivation and impermeable composite structure is formed on the surface of these waste rock slag 1, so that the exposed surface of the fractured rock mass and these waste rock slag 1 are completely isolated from air and water, thereby reducing the generation of acidic wastewater and the spread of pollutants.

[0033] For water inflow and seepage points within the adit that do not exceed the standard, due to the well-developed fissures around them, this embodiment covers the area around these points with a surface-sealing impermeable layer to reinforce the surface and seal off the developed areas. This concentrates the uncontaminated water inflow and seepage, allowing for the organized and concentrated guidance of the uncontaminated water inflow and seepage to be discharged outside the tunnel by a diversion device 5. This achieves the separation of clean and contaminated water inflow and seepage within the adit, reducing the amount of acidic wastewater generated. The diversion device 5 can be an independent diversion pipe or diversion channel.

[0034] For excessive water inflow and seepage points within the adit, this embodiment reinforces the water-stopping structure by grouting around these points. This fills the cracks around the excessive water inflow and seepage points with grout, achieving the purpose of reinforcing the surrounding rock, stopping water flow, and preventing sulfate corrosion. Meanwhile, acidic wastewater flows unorganized to the tunnel entrance by gravity. The acidic wastewater in-situ treatment device intercepts and treats the acidic wastewater in situ, achieving source control of acidic wastewater and preventing further spread of pollutants. This method is particularly suitable for the treatment of continuously inflowing pyrite mine adits in areas with complex geological conditions.

[0035] In detail, the surface-sealed impermeable layer is formed by spraying plain concrete, and 5 kg of cement-based penetrating crystalline waterproofing material and 15%–25% fly ash are added to each cubic meter of concrete. This embodiment, by adding appropriate amounts of cement-based penetrating crystalline waterproofing material and fly ash to the concrete, achieves a concrete strength grade of C30, an impermeability grade of P8, and a sulfate resistance grade of KS150, ensuring the impermeability, strength, and corrosion resistance of the impermeable covering layer 3.

[0036] In one embodiment, the thickness of the surface sealing impermeable layer on the exposed surface of the fractured rock mass is 80mm; from the entrance of the abandoned pyrite mine adit to the water inrush point and seepage point within 3m, the pollution source isolation construction of the tunnel wall is carried out in sections, each section is about 5m long, and the construction is carried out step by step, and the exposed surface of the fractured rock mass is temporarily sealed with plain concrete in the circumferential direction.

[0037] In one embodiment, the thickness of the surface sealing impermeable layer around the non-excessive water inflow point and seepage point is 120mm, and the spraying range is 2m around the non-excessive water inflow point and seepage point.

[0038] In detail, the grouting reinforcement and water-stopping structure is formed by injecting high sulfate-resistant cement grout into the surrounding rock through multi-layered grouting pipes 6 installed around the excessive water inflow and seepage points. Specifically, after the temporary sealing of each exposed section of the tunnel is completed, the grouting pipes 6 are constructed. The grouting pipes 6 are laid out along the upper contour line of the mine tunnel, and holes are drilled using a pneumatic drill. The drilling ends 50cm after the main water inflow or seepage point. Additional holes are drilled at rock fissures or broken rock strata in the lower part of the mine tunnel where there is water inflow and seepage, and grout is subsequently injected. To ensure the integrity of the boreholes, the casing and drill bit are advanced simultaneously during drilling. After drilling is completed, the boreholes are cleaned with compressed air and pressurized water to prevent blockage inside the pipes. After drilling is completed, grouting pipes 6 are installed at an angle from the outside in. Grouting pipes 6 are made of steel pipes with a diameter of 30-40mm and a length of 4-5m. The spacing between grouting holes in the rock section is 100-120mm, and grout outlet holes are evenly distributed at three points around the perimeter. The spacing between steel pipes is 300-500mm, with the smaller value used in areas with seepage or water inflow. The circumferential insertion angle of the steel pipes is 10°. Adjacent rows of grouting pipes 6 should overlap by at least 1m. A sealing hole is installed at the tail of the grouting pipe 6 to prevent grout leakage. During grouting, it must be ensured that the grout is free of impurities. The grout entering the grouting machine must be filtered through a screen. A one-time full-hole grouting method is used, injecting high-sulfate-resistant cement grout to fill the surrounding cracks, achieving the purpose of reinforcing the surrounding rock, stopping water, and preventing sulfate corrosion. After grouting is completed, the sealing hole at the tail of the grouting pipe 6 is sealed.

[0039] In detail, the above embodiment describes an in-situ treatment device for acidic wastewater, comprising a buffer tank 7, a reduction tank 8, a neutralization tank 9, and a sedimentation tank 10 connected sequentially along the flow direction of the acidic wastewater. The acidic wastewater initially flows unorganizedly to the buffer tank 7 for energy dissipation, then gradually returns to a laminar flow state. It then enters the reduction tank 8 under gravity for a reduction reaction to reduce sulfate levels, followed by a neutralization reaction in the neutralization tank 9 to increase alkalinity. Finally, it enters the sedimentation tank 10 to remove heavy metals, thus achieving comprehensive and effective treatment of the acidic wastewater and reducing the risk of environmental pollution.

[0040] Furthermore, a modular gabion structure is installed in buffer tank 7. The gabion modules are filled with limestone with a size of 80-100mm. Acidic wastewater flows through buffer tank 7 by gravity and comes into contact with the limestone, which not only dissipates energy but also increases alkalinity. In one embodiment, the gabion module is a cubic structure, with each module being a cube with a side length of 0.5m. The module assembly is 1.0m high, 2.0m wide, and its length is approximately equal to the width of the opening.

[0041] Furthermore, an organic matter reduction layer is provided at the bottom of the reduction tank 8. The organic matter reduction layer adopts a modular combination structure. Each module includes a cubic shell and organic matter and sulfate-reducing bacteria filled inside the cubic shell. The cubic shell is provided with permeable holes. The organic matter can specifically be a mixture of peat, hay, and soil, with a mass ratio of peat, hay, and soil of 5:4:1. After acidic wastewater passes through the organic matter reduction layer, in an anaerobic environment, the sulfate-reducing bacteria will reduce sulfate to hydrogen sulfide, thereby reducing the sulfate content. In one embodiment, the height of the organic matter reduction layer is 1m, and a 1m high water layer is placed above the organic matter reduction layer. Each module is a cube with a side length of 0.5m, and the module assembly has a height of 1.0m, a width of 2.0m, and a length equivalent to the width of the reduction tank 8.

[0042] Furthermore, a neutralization layer is provided within the neutralization tank 9. The neutralization layer adopts a modular assembly structure. Each module includes a cubic shell and limestone filled within the cubic shell. The cubic shell is provided with permeable pores. The limestone is 3-5mm bagged limestone. When acidic wastewater passes through the neutralization layer, the acidic substances react with the limestone to generate carbon dioxide gas, increasing the alkalinity of the wastewater. In one embodiment, the height of the neutralization layer is 1.5m, and a 0.5m high water layer is placed above the neutralization layer. Each module is a cube with a side length of 0.5m, and the module assembly has a height of 1.5m, a width of 2.0m, and a length approximately equal to the width of the neutralization tank 9.

[0043] Furthermore, the upper part of the sedimentation tank 10 is a 1.5m high reaction zone, and the lower part is a 0.5m high sedimentation zone. The heavy metal ions in the wastewater react fully with the hydrogen sulfide gas generated and transported from the reduction tank 8 to form heavy metal sulfide precipitates that are deposited in the lower part. This part of the precipitate can be periodically removed and transported to the landfill outside the cave for disposal.

[0044] In this embodiment, the reduction tank 8, neutralization tank 9, and sedimentation tank 10 can all be underground reinforced concrete structures, and each tank is a covered closed structure; the buffer tank 7 can be an above-ground structure. In this embodiment, the buffer tank 7, reduction tank 8, neutralization tank 9, and sedimentation tank 10 can be set up independently and connected by pipelines. After a period of operation, the organic matter reduction layer of the reduction tank 8 and the neutralization layer of the neutralization tank 9 will become clogged and need to be cleaned or replaced regularly. In the past, this required overall operation, which consumed a lot of machinery and manpower and took a long time. In this embodiment, the organic matter reduction layer and the neutralization layer are modularized, and lifting lugs are provided on the module. Lifting facilities are provided on the top of the adit, ensuring that the module can slide smoothly from the outside to the inside under the action of gravity, realizing the integrated replacement of agents in the tunnel. Using this device for subsequent agent replacement will greatly increase efficiency.

[0045] Because the acidic wastewater from pyrite reacts with calcium carbonate, hydrogen sulfide, etc., it produces precipitates such as sulfates, hydroxides, and sulfides, which adhere to the organic matter reduction layer and neutralizing agent module. The module needs to be lifted and cleaned regularly. After rinsing, the rinsing water is discharged to the mud-water separation tank, and the bottom mud is regularly removed and transported to the landfill area outside the tunnel for disposal.

[0046] In one embodiment, a hydrogen sulfide gas collection hood 11 is installed at the top of the reduction tank 8. The hydrogen sulfide gas collection hood 11 is connected to the sedimentation tank 10 through a first pipe, and the end of the first pipe is located below the liquid surface of the sedimentation tank 10. Since the sulfate in the acidic wastewater will generate hydrogen sulfide gas under the action of sulfate-reducing bacteria in the reduction tank 8, and hydrogen sulfide gas is a toxic and corrosive gas that will have a negative impact on the environment, this embodiment collects the generated hydrogen sulfide gas through the hydrogen sulfide gas collection hood 11 and introduces it into the sedimentation tank 10. This not only reacts with heavy metals in the wastewater to form metal sulfide precipitates, further reducing the concentration of heavy metals in the effluent, but also achieves waste treatment.

[0047] In this embodiment, the seepage-proof structure on the surface of the waste rock residue 1 at the bottom of the adit includes a passivation layer 2 formed on the surface of the waste rock residue 1 and a seepage-proof covering layer 3 disposed on the surface of the passivation layer 2. The passivation layer 2 is formed by mixing the surface waste rock residue 1 with calcium oxide. In this embodiment, calcium oxide, a remediation agent, is added to the surface waste rock residue 1. Calcium oxide can react with the moisture in the waste rock residue 1 to generate calcium hydroxide, which not only reduces the moisture content of the waste rock residue 1 and neutralizes the acidic substances in the waste rock residue 1, thus reducing the acidity of the waste rock residue 1, but also allows the generated calcium hydroxide to react with the carbon dioxide introduced later to form a calcium carbonate passivation layer 2 that coats the waste rock residue 1, thereby improving the physical and chemical stability of the waste rock residue 1. Preferably, the amount of calcium oxide used is 1-3% of the mass of the surface waste rock residue 1.

[0048] The specific construction method for the seepage prevention structure is as follows: First, the waste rock slag 1 at the bottom surface of the adit is mixed evenly with a certain amount of calcium oxide to form a passivation layer 2 of a certain thickness. Then, the passivation layer 2 is leveled and compacted. Finally, concrete is sprayed completely onto the surface of the passivation layer 2 as a seepage prevention covering layer 3 to prevent water inflow and seepage into the passivation layer 2. Further, the thickness of the passivation layer 2 is 0.8–1.2 m, the thickness of the seepage prevention covering layer 3 is 80–150 mm, and the concrete strength grade of the seepage prevention covering layer 3 is C25, the frost resistance grade is F150, and the seepage resistance grade is P8. Preferably, the thickness of the passivation layer 2 is 1 m, and the thickness of the seepage prevention covering layer 3 is 100 mm.

[0049] In an optimized embodiment, a carbon dioxide collection hood 12 is installed at the top of the neutralization tank 9, and a gas distribution pipe 4 is installed inside the passivation layer 2. The carbon dioxide collection hood 12 is connected to the gas distribution pipe 4 through a second pipe. Since the acidic substances in the acidic wastewater react with the limestone in the neutralization tank 9 to produce carbon dioxide gas, this embodiment collects the generated carbon dioxide gas through the carbon dioxide collection hood 12 and introduces it into the passivation layer 2 of the residual waste rock slag 1. This not only reacts with the calcium hydroxide on the surface of the waste rock slag 1 in the passivation layer 2 to form a calcium-based carbonate passivation layer 2 that encapsulates the waste rock slag 1, improving the physical and chemical stability of the waste rock slag 1 and further controlling the pollution of the residual waste rock slag 1, but also achieves waste-to-waste treatment.

[0050] The air distribution pipe 4 can be made of high-density polyethylene (HDPE). Multiple layers of air distribution pipes 4 can be arranged within the passivation layer 2, with multiple air distribution pipes 4 spaced apart in each layer. The number of layers and the spacing between each layer of air distribution pipes 4 can be designed according to the thickness of the passivation layer 2 and the specific situation of the remaining waste rock slag 1. They can be pre-embedded in the passivation layer 2 during the construction of the seepage prevention structure. In one embodiment, two layers of air distribution pipes 4 are arranged from top to bottom within the passivation layer 2. The distance between the upper layer of air distribution pipes 4 and the seepage prevention covering layer 3 is 8-15cm, preferably 10cm; the distance between the lower layer of air distribution pipes 4 and the seepage prevention covering layer 3 is 45-55cm, preferably 50cm.

[0051] In an optimized embodiment, the hydrogen sulfide gas collection hood 11 is also connected to the gas distribution pipe 4 via a third pipe. This embodiment can also introduce the hydrogen sulfide generated in the reduction tank 8 into the passivation layer 2 of the remaining waste rock slag 1. This not only reacts with heavy metal ions on the surface of the waste rock slag 1 to generate metal sulfides, stabilizing the heavy metal ions and reducing their migration and release into the surrounding environment, but also achieves waste-to-waste treatment.

[0052] Furthermore, valves #1, #2, and #3 can be installed on the first, second, and third pipelines respectively. Valves #1 and #3 are used to control the delivery of hydrogen sulfide gas to the sedimentation tank 10 and the waste rock slag 1, respectively, and valve #2 is used to control the delivery of carbon dioxide gas to the waste rock slag 1.

[0053] In this embodiment, a hydrogen sulfide gas sensor can also be installed in the hydrogen sulfide gas collection hood 11 to monitor the concentration of hydrogen sulfide gas in the hydrogen sulfide gas collection hood 11 in real time; and a carbon dioxide gas sensor can be installed in the carbon dioxide gas collection hood 12 to monitor the concentration of carbon dioxide gas in the carbon dioxide gas collection hood 12 in real time.

[0054] In one embodiment, at least two acidic wastewater in-situ treatment devices are arranged in parallel, completely covering the overflow area of ​​the acidic wastewater. Because multiple acidic wastewater in-situ treatment devices operate in parallel, each device can be individually shut down for system maintenance, sludge cleaning, or clogging flushing. The cleaning water source can utilize uncontaminated gushing and seepage water diverted by the diversion device 5. Water pressure can fully utilize natural elevation differences or employ portable equipment. The resulting muddy water is collected in a mud-water separation tank.

[0055] Example 2

[0056] This invention also provides a method for treating acidic wastewater from abandoned pyrite mine adits, comprising the following steps:

[0057] First, investigate the exposed surface of the fractured rock mass, water inflow points, and seepage points inside the adit of the abandoned pyrite mine. Investigate, sample, and test the main water inflow points and seepage points on the bedrock surface inside the tunnel to determine the extent of pollution.

[0058] Then, based on the exploration and testing results, the acidic wastewater source treatment system described above for any of the above-mentioned acidic wastewater sources in the abandoned pyrite mine adit is implemented. This system isolates the exposed surface of the fractured rock mass and the waste rock residue 1 left at the bottom of the adit from the water, diverts uncontaminated gushing and seepage water to the outside of the tunnel for discharge, and collects the acidic wastewater to the acidic wastewater in-situ treatment device for in-situ treatment before discharging it outside the tunnel after it meets the standards. Specifically, a surface sealing anti-seepage layer is first applied to the exposed surface of the fractured rock mass. Then, a grouting reinforcement water-stopping structure is applied around the excessive gushing and seepage points. A surface sealing anti-seepage layer is applied around the non-excessive gushing and seepage points. After the strength is reached, a diversion device 5 is installed around the non-excessive gushing and seepage points. The waste rock residue 1 left at the bottom of the adit is leveled on-site and an anti-seepage structure is applied to its surface. Then, the acidic wastewater in-situ treatment device is constructed at the tunnel entrance.

[0059] After entering the acidic wastewater in-situ treatment device, the wastewater sequentially flows into buffer tank 7, reduction tank 8, neutralization tank 9, and sedimentation tank 10. The acidic wastewater passes through buffer tank 7 by gravity, thus achieving energy dissipation. In the reduction zone, sulfates in the acidic wastewater are reduced to hydrogen sulfide by sulfate-reducing bacteria. In the neutralization zone, acidic substances in the wastewater react with limestone to generate carbon dioxide. Heavy metal ions in the acidic wastewater precipitate in sedimentation tank 10, thus removing heavy metals.

[0060] After hydrogen sulfide is generated in reduction tank 8, valve #3 is opened first, and valves #1 and #2 are closed. The hydrogen sulfide gas generated in reduction tank 8 is introduced into the passivation layer 2 of waste rock slag 1. The hydrogen sulfide reacts with the heavy metal ions on the surface of waste rock slag 1 to form metal sulfides, thereby stabilizing the heavy metal ions. Then, valve #3 is closed, and valves #1 and #2 are opened. The carbon dioxide gas generated in neutralization tank 9 is introduced into the passivation layer 2 of waste rock slag 1. The carbon dioxide reacts with the calcium hydroxide on the surface of waste rock slag 1 in passivation layer 2 to form calcium carbonate passivation layer 2, which encapsulates the waste rock slag 1. The hydrogen sulfide gas generated in reduction tank 8 is then introduced into sedimentation tank 10. The hydrogen sulfide reacts with the heavy metals in the wastewater to form metal sulfide precipitates, further reducing the concentration of heavy metals in the effluent.

[0061] This embodiment addresses the problem of managing continuously inflowing pyrite mine tunnels in areas with complex geological conditions by implementing in-situ tunnel wall seepage prevention, clear water diversion, waste residue sealing, and wastewater treatment. This avoids a series of problems associated with using a single sealing and treatment solution.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system for treating the source of acid wastewater in a waste pyrite mine adit, characterized in that: The acid waste water in-situ treatment device, a flow guide device, a seepage prevention structure arranged on the surface layer of the residual waste rock and slag at the bottom of the adit, a grouting reinforced water stop structure arranged around the over-standard gushing water point and the seepage point, and a surface sealing impermeable layer arranged around the exposed surface of the broken rock mass, the over-standard gushing water point and the seepage point; The acid waste water in-situ treatment device is arranged at the adit opening and used for collecting and treating the acid waste water formed by the over-standard gushing water point and the seepage point; The flow guide device has one end located below the over-standard gushing water point and the seepage point and the other end extended to outside of the adit, and is used for guiding the unpolluted gushing water and seepage water to outside of the adit for discharge; 2. The abandoned pyrite mine adit acid wastewater source head treatment system according to claim 1, characterized in that: The acid waste water in-situ treatment device comprises a buffer pool, a reduction pool, a neutralization pool and a sedimentation pool which are sequentially communicated along the flow direction of the acid waste water; the seepage prevention structure comprises a passivation layer formed on the surface layer of the residual waste rock and slag and an impermeable cover layer arranged on the surface of the passivation layer, and the passivation layer is formed by turning over the surface layer of the waste rock and slag and calcium oxide; the top of the neutralization pool is provided with a carbon dioxide gas collecting hood, the passivation layer is provided with a gas distribution flower pipe, and the carbon dioxide gas collecting hood is communicated with the gas distribution flower pipe through a second pipeline; the top of the reduction pool is provided with a hydrogen sulfide gas collecting hood, and the hydrogen sulfide gas collecting hood is communicated with the gas distribution flower pipe through a third pipeline.

3. The abandoned pyrite mine adit acid wastewater source head treatment system according to claim 2, characterized in that: The surface sealing impermeable layer is formed by spraying plain concrete, and 5 kg of cement-based permeable crystalline waterproof material and 15% to 25% of fly ash are mixed in each cubic meter of concrete.

4. The abandoned pyrite mine adit acid wastewater source head treatment system according to claim 1, characterized in that: The grouting reinforced water stop structure is formed by injecting high sulfate-resistant cement grout into the surrounding rock through the multilayer grouting pipes arranged around the over-standard gushing water point and the seepage point.

5. The abandoned pyrite mine adit acid wastewater source head treatment system according to claim 1, characterized in that: The hydrogen sulfide gas collecting hood is communicated with the sedimentation pool through a first pipeline, and the end of the first pipeline is located below the liquid surface of the sedimentation pool.

6. A method for treating the source of acid wastewater in a waste pyrite mine adit, characterized in that, The acid waste water in-situ treatment device has at least two and is arranged in parallel and covers the acid waste water flow range completely. The method comprises the following steps: Firstly, the exposed surface of the broken rock mass, the gushing water point and the seepage point in the abandoned pyrite mine adit are investigated, the main gushing water point and the seepage point of the bedrock surface in the adit are investigated, sampled and detected, and the pollution condition is determined; Then, according to the investigation and the detection result, the abandoned pyrite mine adit acid waste water source treatment system is constructed in the abandoned pyrite mine adit, the exposed surface of the broken rock mass and the bottom of the adit are isolated from water, the unpolluted gushing water and seepage water are guided to outside of the adit for discharge, the acid waste water is collected into the acid waste water in-situ treatment device and sequentially enters the buffer pool, the reduction pool, the neutralization pool and the sedimentation pool, the sulfate in the acid waste water is reduced to hydrogen sulfide by sulfate-reducing bacteria in the reduction zone, the acid substance in the acid waste water reacts with limestone to generate carbon dioxide in the neutralization zone; after the hydrogen sulfide is generated in the reduction pool, the hydrogen sulfide is first introduced into the residual waste rock and slag to react with the heavy metals in the waste rock and slag to generate metal sulfide, then the carbon dioxide gas generated in the neutralization pool is introduced into the residual waste rock and slag to react with the surface layer of the calcium oxide in the waste rock and slag to generate calcium carbonate passivation layer, and the hydrogen sulfide is introduced into the sedimentation pool to react with the heavy metals in the waste water to generate metal sulfide precipitation.

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