A method for treating mining area wastewater

Abstract

The present invention relates to the technical field of wastewater treatment, and discloses a method for treating mine wastewater, comprising the following steps: constructing a surface water drainage channel in the mining area that is connected to each mine shaft, and connecting the surface water drainage channel to a downstream watercourse to intercept and divert rainwater, so as to minimize the supply of surface water to the mine shaft; plugging all the mine shafts in the mining area to maximize the interception of the groundwater runoff entering the mine pit; arranging precipitation drainage wells at positions close to the mine shafts in the mining area, the precipitation drainage wells comprising well holes and well pipes, and the well holes sequentially passing through the upper aquifer and the ore layer and extending into the lower aquifer below the ore layer; The method for treating mine wastewater provided by the present invention solves the problem that the prior art cannot effectively treat the generation of wastewater from the source.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a method for treating mining wastewater. Background Art

[0002] The main source of groundwater in the mining area is atmospheric precipitation. After the precipitation penetrates into the mineral-bearing strata, it will be polluted by the mineral-bearing strata. Therefore, acidic mine water exists in the mine for a long time. The water carries a large amount of acidic substances and metal elements such as iron, manganese, and zinc, which are extremely polluting. The mine water flows through the nearby soil, which not only causes a reduction in local crop yields and even the abandonment of cultivated land, but also the wastewater enters the nearby water bodies, causing the water bodies to deteriorate and pollute the environment.

[0003] Acid mine wastewater has a low pH value and is highly corrosive. It also contains many heavy metal elements. Discharge to the surface will cause large-scale surface water pollution. Heavy metal ions will consume dissolved oxygen in the water, reduce the water's own purification capacity, and have adverse effects on the growth of freshwater animals and plants, causing the death and extinction of a large number of fish and algae plankton in the water. At the same time, acid wastewater will destroy the soil structure and may cause the death of crops. Acid mine wastewater is mainly sulfate-based, and the product of sulfate biodegradation is mainly hydrogen sulfide. H2S itself is toxic and has a very bad smell, which seriously pollutes the air and has adverse effects on the human body.

[0004] The infiltration modes of atmospheric precipitation are surface infiltration and concentrated point recharge. Surface infiltration mainly infiltrates through loose surface soil layers, while concentrated point infiltration mainly infiltrates through karst cracks and karst channels in the mining area, unsealed mine caves, and boreholes. Atmospheric precipitation enters the Changxing Formation (P3c) aquifer of the Upper Permian System overlying the ore layer. This layer overlies the mineral-bearing strata and constitutes an indirect roof water-filled aquifer of the ore deposit, with weak to medium water-richness. This layer is mainly composed of medium-thick to thick-layered limestone, and weathering cracks, structural cracks, and karst cracks constitute channels for groundwater to infiltrate downward. If the mine is not sealed, groundwater will continue to infiltrate downward under the control of the terrain and enter the Longtan Formation (P31) of the Upper Permian System. The water-bearing medium in this layer is poorly developed and the recharge conditions are not good. The terrain is conducive to drainage and contains fissure water. The mineable coal seam is stored in this layer, which has constituted a direct water-filled aquifer of the ore deposit. During the mining process, the integrity of the rock mass has been destroyed on a large scale, forming multiple old mines, and the water-conducting fracture zone will touch this layer, especially the M9 coal seam about 50m away from the bottom of P3c. When the M9 coal seam is mined, a large area of goaf will be formed, which may cause ground collapse. It has been transformed from a relatively impermeable layer to a large area of permeable layer. At that time, the groundwater in this layer will indirectly enter the shaft and tunnel through the water-conducting fracture zone and the collapse zone, affecting the water filling of the shaft and tunnel. The groundwater migrates in this layer, carrying harmful substances in the ore layer, and is finally discharged at low-lying locations such as the cave entrance. This is also a direct factor for the mine water to gush out of the cave entrance.

[0005] In response to the problem of wastewater gushing out of mine mouths, the common practice at present is to seal the water-conducting fissures in the mine to isolate the wastewater, that is, to use the curtain grouting process in the mining area to isolate the mine wastewater from gushing out. However, the problem with this method is that even if the fissures are sealed, groundwater will continue to infiltrate, so leakage will still occur in other places in the mine. Therefore, simply sealing the mine cannot effectively isolate the wastewater, and it cannot fundamentally solve the problem of wastewater generation.

[0006] Of course, it is also possible to isolate the outflow of mine wastewater by building a sewage treatment station downstream of the mining area and using curtain grouting technology in the mining area, but this plan requires huge initial investment and high later use costs. The annual operating expenses are also a considerable amount. Due to the large investment and long construction period, and if the mining area is surrounded by farmland or the terrain is gully, it cannot be implemented. In addition, the operation of the equipment also consumes energy, which is not conducive to energy conservation and environmental protection. It can be seen that the combination of building a sewage treatment station and using curtain grouting technology not only has financial and construction implementation obstacles, but also cannot fundamentally solve the problem of wastewater that has already been generated.

[0007] As mentioned above, after long-term mining, the surrounding soil has been polluted. In order to protect the health of surrounding residents and the safety of crop growth, it is urgently necessary to propose a mine wastewater treatment method that can completely solve the problem of mine wastewater generation. Summary of the invention

[0008] The purpose of the present invention is to provide a method for treating mining wastewater to solve at least one of the above problems existing in the prior art.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for treating mining wastewater mainly includes groundwater source drainage control, key pollutant isolation and sludge centralized treatment, and specifically includes the following steps:

[0011] Constructing surface water drainage channels in the mining area that are connected to various mines. The surface water drainage channels are connected to downstream waterways to intercept and drain rainwater, thereby minimizing the amount of surface water used to supplement the mines;

[0012] All mine shafts in the mining area are sealed to minimize the groundwater runoff into the mines;

[0013] Rainwater drainage wells are arranged near the mine in the mining area. The rainwater drainage wells include well holes and well pipes. The well holes sequentially pass through the upper aquifer and the ore layer and then extend into the lower aquifer below the ore layer. Well pipes are provided in the well holes. The well pipes include upper water-permeable pipes, middle isolation pipes, and lower water-permeable pipes that are sequentially connected from top to bottom. The upper water-permeable pipes are located above the ore layer, the lower water-permeable pipes are located below the ore layer, and the middle isolation pipes are used to isolate the ore layer.

[0014] In this technical solution, the treatment of mine wastewater adopts the technical route of surface drainage and anti-seepage and underground rainwater drainage. On the basis of clarifying the hydrogeological conditions of the mining area, a comprehensive treatment method combining above-ground and underground is adopted. The above-ground project is mainly the construction of surface water drainage channels and the sealing project of the mine, and the underground project is mainly the setting of several rainwater drainage wells in the mining area.

[0015] First, the surface water drainage channels lead the surface water out of the mining area, minimizing the replenishment of surface water to the mine. Secondly, the mine is sealed, that is, the groundwater runoff channel is sealed, thus maximizing the interception of the groundwater runoff entering the mine pit. In summary, the construction of the surface water drainage channels and the sealing of the mine can reduce the infiltration recharge of surface water bodies. Finally, underground rainwater drainage wells are used to lower the groundwater level in the mining area, so that the uncontaminated water above the ore layer seeps down through the rainwater drainage wells into the lower aquifer, such as the Maokou Formation aquifer, and diffuses around. The surface karst of the Maokou Formation aquifer is relatively developed, with good recharge conditions and strong water-richness, and can be discharged through the underground river system, thus effectively controlling the water inrush source of the mine. Combining the above treatment methods of surface drainage and anti-seepage and underground rainwater drainage, this technical solution achieves the purpose of no polluted water flow on the surface, treats from the source, prevents water resources from being polluted, effectively protects the water resource balance, and solves the mine water pollution problem once and for all from the root cause.

[0016] Specifically, since a well hole is provided near the mine, the well hole sequentially passes through the upper aquifer and the ore seam and then extends into the lower aquifer below the ore seam. According to the actual situation, the lower aquifer can be the Maokou Formation aquifer or other strata below this layer. The well pipe includes an upper permeable pipe, a middle isolation pipe, and a lower permeable pipe that are sequentially connected from top to bottom. Since the ore seam has weak water-richness and a large thickness, it is a good water isolation layer in the mining area. And due to the existence of silt and fine sand interlayers and lens bodies and the directional arrangement of clay particles during the sedimentation process of the soil, the horizontal permeability coefficient is often greater than the vertical permeability coefficient. Therefore, when surface water has not penetrated into the ore seam or only a small amount of surface water has penetrated into the ore seam, the upper permeable pipe located above the ore seam can ensure that the surface water smoothly penetrates into the precipitation drainage well. And near the precipitation drainage well, the surface water will penetrate towards the precipitation drainage well in a funnel shape with the center of the precipitation drainage well as the reference, so as to minimize the infiltration of surface water into the ore seam from the vertical direction and cause groundwater pollution; the setting of the middle isolation pipe can isolate the ore seam, that is, the water source polluted by the ore seam cannot flow into the precipitation drainage well, thus realizing the isolation of the wastewater generated in the ore seam, and the water entering the precipitation drainage well will not be affected by the ore seam; the setting of the lower permeable pipe enables the uncontaminated water source in the well to penetrate into the Maokou Formation aquifer through the lower permeable pipe and diffuse around. The surface karst of the Maokou Formation aquifer is relatively developed, the recharge condition is good, and the water-richness is strong, and it can be discharged through the underground river system. The precipitation drainage well provided by this technical solution leads the surface water to the Maokou Formation aquifer with strong deep water permeability through the well pipe of the precipitation drainage well. When a large amount of surface water bypasses the ore seam and is introduced into the deep rock layer with strong water permeability, it can greatly reduce the pollution of the surface water by the ore seam, and the water source penetrating into the ore seam is significantly reduced, which also directly solves the problem of wastewater generated by mine water inflow from the source. The implementation of this technical solution can directly reduce the heavy metal pollution in the water body and soil of the mining area, which has a positive effect on solving the historical legacy problems of the mining area and improving the regional ecological environment. And by controlling seepage precipitation to solve the problem of mine water pollution, the relative investment is small and the construction period is short.

[0017] In summary, this technical solution treats from the source, prevents water resources from being polluted, effectively protects the water resource balance, and fundamentally solves the problem of mine water pollution once and for all.

[0018] It should be noted that the infiltration modes of atmospheric precipitation are surface infiltration and concentrated point recharge. Surface infiltration mainly infiltrates through loose surface soil layers, and concentrated point infiltration mainly infiltrates through karst rock cracks and karst channels in the mining area, unsealed mine caves, and boreholes (holes). Atmospheric precipitation enters the Changxing Formation (P3c) aquifer of the Upper Permian System overlying the ore layer. This layer overlies the mineral-bearing strata and constitutes an indirect roof water-filled aquifer of the ore deposit, with weak to medium water-richness. This layer is mainly composed of medium-thick to thick-layered limestone. Weathering fissures, structural fissures, and karst fissures constitute downward infiltration channels for groundwater. Therefore, this technical solution blocks the groundwater runoff entering the mine pit to the maximum extent by blocking the mine.

[0019] If the mine is not sealed, groundwater will continue to infiltrate downward under the control of the terrain and enter the Longtan Formation (P31) of the Upper Permian System. The water-bearing medium in this layer is poorly developed and the recharge conditions are not good. The terrain is conducive to drainage and contains fissure water. The mineable coal seam is stored in this layer, which has constituted a direct water-filled aquifer of the ore deposit. During the mining process, the integrity of the rock mass has been destroyed on a large scale, forming multiple old mines, and the water-conducting fracture zone will touch this layer, especially the M9 coal seam about 50m away from the bottom of P3c. When the M9 coal seam is mined, a large area of goaf will be formed, which may cause ground collapse. It has been transformed from a relatively impermeable layer to a large area of permeable layer. At that time, the groundwater in this layer will indirectly enter the shaft and tunnel through the water-conducting fracture zone and the collapse zone, affecting the water filling of the shaft and tunnel. The groundwater migrates in this layer, carrying harmful substances in the ore layer, and is finally discharged at low-lying locations such as the cave entrance. This is also a direct factor for the mine water to gush out of the cave entrance.

[0020] Therefore, this technical solution, first of all, designs surface water drainage channels to lead surface water out of the mining area, minimizing the amount of surface water replenishing the mine; secondly, by blocking the mine, the groundwater runoff entering the mine is blocked to the greatest extent; finally, a precipitation diversion well is designed to lead the groundwater that has infiltrated the upper aquifer into the well, thereby effectively controlling the source of water gushing from the mine and solving the problem of water gushing from the source.

[0021] This technical solution can control mining pollution at the source, thus achieving comprehensive remediation of the historically polluted environment in the region. It is also a related technology for regional water pollution control and can directly reduce heavy metal pollution in mining area water and soil. It plays a positive role in solving historical problems and improving the regional ecological environment.

[0022] The implementation of this plan requires regional hydrogeological surveys to understand precipitation and water quality changes. This plan solves the problem of mine water pollution by controlling seepage precipitation and surrounding surface drainage, with relatively small investment and short construction period.

[0023] Further, in order to achieve a better plugging effect, the plugging length of the mine can extend 10 m inward from the mine entrance and is determined according to the hydrogeological survey results.

[0024] Further, in order to achieve precipitation drainage near the mine over a larger area and divert it into the well, reducing the infiltration of water into the mine or the ore layer, the number of the precipitation drainage wells is not less than the number of mines in the mining area, and the positions of the precipitation drainage wells are distributed near the mine entrance or along the extension direction of the main mine tunnel.

[0025] Further, in order to enhance the precipitation drainage effect and realize the diversion of groundwater in a timely manner, three precipitation drainage wells are respectively arranged near the mine entrance and along the extension direction of the main mine tunnel.

[0026] Further, for each mine, in order to minimize the pollution of groundwater as much as possible, the spacing between adjacent precipitation drainage wells can be 80 m - 150 m, which is specifically determined according to the data of hydrogeological test results.

[0027] Further, in order to prevent groundwater from entering the mine through the collapsed area and causing mine water inrush, if there is a collapsed area in the mine, the collapsed area in the mine is filled and the sludge is cleaned up.

[0028] Further, the sludge in the original drainage ditch in the mining area is cleaned up, and the cleaned sludge is transported away or used to fill the collapsed area. Cleaning the sludge in the original drainage ditch can reduce the overflow of mining area wastewater and its impact on the surrounding soil.

[0029] Further, in order to enhance the drainage effect and service life of the surface water drainage channel, the inner wall of the surface water drainage channel is cast with concrete, and the cross-section of the surface water drainage channel is a rectangular section.

[0030] Further, in order to remove the polluted soil layer in the mining area as much as possible and restore the ecological environment of the mining area to a certain extent, it also includes removing the polluted soil layer on the surface of the mining area, and the removed soil layer is centrally landfilled.

[0031] Further, in order to better plug the mine, during the plugging process of the mine, curtain grouting is carried out on the fissure karst development zone to block the groundwater runoff channel.

[0032] The beneficial effects of the present invention are as follows: In this technical solution, the treatment of mining area wastewater adopts the technical route of surface drainage and anti-seepage and underground precipitation drainage. On the basis of clarifying the hydrogeological conditions of the mining area, a comprehensive treatment is carried out in a combination of above-ground and underground methods. The above-ground projects are mainly the construction of surface water drainage channels and the mine plugging project, and the underground projects are mainly the installation of several precipitation drainage wells in the mining area.

[0033] First, surface water drainage channels lead surface water out of the mining area to minimize the replenishment of surface water to the mine. Secondly, the mine is sealed, that is, the groundwater runoff channels are blocked, thus maximizing the interception of groundwater runoff into the mine pit. In summary, the construction of surface water drainage channels and the sealing of the mine can reduce the infiltration recharge of surface water bodies when combined. Finally, precipitation drainage wells are used underground to lower the groundwater level in the mining area, allowing the uncontaminated water above the ore layer to infiltrate into the lower aquifer through the precipitation drainage wells, such as the Maokou Formation aquifer, and diffuse around. The surface karst of the Maokou Formation aquifer is relatively developed, with good recharge conditions and strong water-richness, and can be discharged through the underground river system, thus effectively controlling the source of mine water inrush. Combining the above treatment methods of surface water diversion and anti-seepage and underground water precipitation and drainage, this technical solution achieves the purpose of pollution-free surface water flow, treats from the source, prevents water resources from being polluted, effectively protects the water resource balance, and solves the mine water pollution problem once and for all from the root cause.

[0034] Specifically, since a well hole is provided near the mine, the well hole sequentially passes through the upper aquifer and the ore seam and then extends into the lower aquifer below the ore seam. According to the actual situation, the lower aquifer can be the Maokou Formation aquifer or other strata below this layer. The well pipe includes an upper permeable pipe, a middle isolation pipe, and a lower permeable pipe connected in sequence from top to bottom. Since the ore seam has weak water-richness and a large thickness, it is a good water isolation layer in the mining area. And due to the existence of fine silt interlayers and lenses and the directional arrangement of clay particles during the sedimentation process of the soil, the horizontal permeability coefficient is often greater than the vertical permeability coefficient. Therefore, when surface water has not penetrated into the ore seam or only a small amount has penetrated into the ore seam, the upper permeable pipe located above the ore seam can ensure that the surface water smoothly penetrates into the precipitation drainage well. And near the precipitation drainage well, the surface water will penetrate towards the precipitation drainage well in a funnel shape with the center of the precipitation drainage well as the reference, so as to minimize the infiltration of surface water into the ore seam from the vertical direction and cause groundwater pollution; the setting of the middle isolation pipe can isolate the ore seam, that is, the water source polluted by the ore seam cannot flow into the precipitation drainage well, thus realizing the isolation of the wastewater generated in the ore seam, and the water entering the precipitation drainage well will not be affected by the ore seam either; the setting of the lower permeable pipe enables the uncontaminated water source in the well to penetrate into the Maokou Formation aquifer through the lower permeable pipe and diffuse around. The surface karst of the Maokou Formation aquifer is relatively developed, the recharge condition is good, and the water-richness is strong, and it can be discharged through the underground river system. The precipitation drainage well provided by this technical solution leads the surface water to the Maokou Formation aquifer with strong deep water permeability through the well pipe of the precipitation drainage well. When a large amount of surface water bypasses the ore seam and is introduced into the deep rock layer with strong water permeability, it can greatly reduce the pollution of the surface water by the ore seam, and the water source penetrating into the ore seam is significantly reduced, which also directly solves the problem of wastewater generated by mine water inflow from the source. The implementation of this technical solution can directly reduce the heavy metal pollution in the water body and soil of the mining area, which has a positive effect on solving the historical problems left over in the mining area and improving the regional ecological environment. And by controlling the seepage precipitation to solve the problem of mine water pollution, the relative investment is small and the construction period is short.

[0035] In summary, this technical solution treats from the source, prevents water resources from being polluted, effectively protects the water resource balance, and fundamentally solves the problem of mine water pollution once and for all. Brief Description of the Drawings

[0036] Figure 1 It is a schematic structural diagram of the precipitation drainage test well in the present invention;

[0037] Figure 2 It is a top-view structural diagram of the layout state of four precipitation drainage wells in the present invention;

[0038] Figure 3 It is a three-dimensional structural diagram of the layout state of four precipitation drainage wells in the present invention;

[0039] Figure 4 It is a schematic cross-sectional structure diagram of a precipitation diversion test well in the present invention;

[0040] Figure 5 is Figure 4 the cross-sectional view at A-A in;

[0041] Figure 6 It is a schematic top view structure diagram of a reinforced concrete cover plate in the present invention;

[0042] Figure 7 is Figure 6 the cross-sectional view at B-B in;

[0043] Figure 8 is Figure 6 the cross-sectional view at C-C in;

[0044] Figure 9 It is the distribution of precipitation diversion test wells in the mining area;

[0045] Figure 10 It is the schematic diagram of the precipitation diversion well principle in the present invention;

[0046] Figure 11 It is the schematic diagram of the groundwater funnel in the mine area in the present invention.

[0047] In the figure: well hole 1; upper permeable pipe 2; middle isolation pipe 3; lower permeable pipe 4; aquifer 5; ore layer 6; Maokou formation aquifer 7; reinforced concrete cover plate 8; wellhead hole 9; stabilizing platform 10; backfill soil layer 11; cover plate handle 12; drawdown funnel 13. Specific embodiments

[0048] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the present invention in combination with the accompanying drawings and the description of the embodiments or the prior art. Obviously, the following description of the structure of the drawings is only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. It should be noted here that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation to the present invention.

[0049] Embodiment 1:

[0050] As Figures 1 - 11 shown, this embodiment provides a method for treating wastewater in a mining area, which mainly includes groundwater source diversion control, key pollution isolation, and sludge centralized treatment, and specifically includes the following steps:

[0051] Build surface water drainage channels within the mining area that are connected to each mine shaft. The surface water drainage channels are connected to the downstream watercourse to intercept and divert rainwater, minimizing the recharge of surface water to the mine shafts to the greatest extent possible.

[0052] Seal all the mine shafts in the mining area to intercept the groundwater runoff into the mine pits to the greatest extent possible.

[0053] Install precipitation drainage wells near the mine shafts within the mining area. The precipitation drainage wells include well hole 1 and a well pipe. Well hole 1 sequentially passes through the upper aquifer 5 and the ore layer 6 and then extends into the lower aquifer below the ore layer. A well pipe is provided in well hole 1. The well pipe includes an upper permeable pipe 2, a middle isolation pipe 3, and a lower permeable pipe 4 that are connected in sequence from top to bottom. The upper permeable pipe 2 is located above the ore layer 6, the lower permeable pipe 4 is located below the ore layer 6, and the middle isolation pipe 3 is used to isolate the ore layer 6.

[0054] In this technical solution, the treatment of mining area wastewater adopts a technical route of surface water diversion and anti-seepage and underground precipitation drainage. On the basis of clarifying the hydrogeological conditions of the mining area, a comprehensive treatment method combining above-ground and underground is adopted. The above-ground projects mainly include the construction of surface water drainage channels and the mine shaft sealing project, and the underground projects mainly include the installation of several precipitation drainage wells within the mining area.

[0055] First, the surface water drainage channels divert surface water out of the mining area, minimizing the recharge of surface water to the mine shafts to the greatest extent possible. Second, seal the mine shafts, that is, block the groundwater runoff channels, thereby intercepting the groundwater runoff into the mine pits to the greatest extent possible. In summary, the construction of surface water drainage channels and the sealing of mine shafts can reduce the infiltration recharge of surface water bodies when combined. Finally, underground precipitation drainage wells are used to lower the groundwater level in the mining area, allowing the uncontaminated water above the ore layer 6 to infiltrate into the lower aquifer through the precipitation drainage wells, such as into the Maokou Formation aquifer 7, and diffuse around. The surface karst of the Maokou Formation aquifer 7 is relatively developed, with good recharge conditions and strong water-richness, and can be discharged through the underground river system, thus effectively controlling the source of mine water inrush. Combining the above treatment methods of surface water diversion and anti-seepage and underground precipitation drainage, this technical solution achieves the purpose of having no polluted surface water flow, treating from the source, preventing water resources from being polluted, effectively protecting the water resource balance, and fundamentally solving the mining area water pollution problem once and for all.

[0056] Specifically, since a well hole 1 is provided near the mine, the well hole 1 sequentially passes through the upper aquifer 5 and the ore seam 6 and then extends into the lower aquifer below the ore seam. According to the actual situation, the lower aquifer can be the Maokou Formation aquifer 7 or other strata below this layer. The well pipe includes an upper permeable pipe 2, a middle isolation pipe 3, and a lower permeable pipe 4 connected in sequence from top to bottom. Since the ore seam 6 has weak water-richness and a large thickness, it is a good water isolation layer in the mining area. Moreover, due to the existence of silt and fine sand interlayers and lenses and the directional arrangement of clay particles during the sedimentation process of the soil, the horizontal permeability coefficient is often greater than the vertical permeability coefficient. Therefore, when surface water has not penetrated into the ore seam 6 or only a small amount of surface water has penetrated into the ore seam 6, the upper permeable pipe 2 located above the ore seam 6 can ensure that the surface water smoothly penetrates into the precipitation drainage well. And near the precipitation drainage well, the surface water will penetrate towards the precipitation drainage well in a funnel shape with the center of the precipitation drainage well as the reference, thereby being able to minimize the infiltration of surface water into the ore seam 6 from the vertical direction and causing groundwater pollution; the setting of the middle isolation pipe 3 can isolate the ore seam 6, that is, the water source polluted by the ore seam 6 cannot flow into the precipitation drainage well, thus realizing the isolation of the wastewater generated in the ore seam 6, and the water entering the precipitation drainage well will not be affected by the ore seam 6; the setting of the lower permeable pipe 4 enables the uncontaminated water source in the well to penetrate into the Maokou Formation aquifer 7 through the lower permeable pipe 4 and diffuse around. The surface karst of the Maokou Formation aquifer 7 is relatively developed, the recharge condition is good, and the water-richness is strong, and it can be discharged through the underground river system. The precipitation drainage well provided by this technical solution leads the surface water to the Maokou Formation aquifer 7 with strong deep permeability through the well pipe of the precipitation drainage well. When a large amount of surface water bypasses the ore seam 6 and is introduced into the deep rock layer with strong permeability, it can greatly reduce the pollution of the surface water by the ore seam 6, and the water source penetrating into the ore seam 6 is significantly reduced, which also directly solves the problem of mine water inflow generating wastewater from the source. The implementation of this technical solution can directly reduce the heavy metal pollution in the water body and soil of the mining area, has a positive effect on solving the historical problems left in the mining area and improving the regional ecological environment, and solves the problem of mine water pollution through seepage precipitation control, with relatively small investment and short construction period.

[0057] In summary, this technical solution treats from the source, prevents water resources from being polluted, effectively protects the water resource balance, and solves the problem of mine water pollution once and for all from the root cause.

[0058] It should be noted that a regional groundwater drawdown funnel 13 will be formed in the mining area, thereby effectively reducing the groundwater level and achieving the effect of basically no surface runoff. Preferably, as Figure 2 、 Figure 3 shown, 4 - 6 precipitation drainage wells can be arranged near each mine.

[0059] It should be noted that there is an aquifer in the Upper Permian Changxing Formation (P3c) above the overlying ore-bearing strata. This layer is mainly composed of medium-thick to thick-bedded limestone. Weathering fissures, tectonic fissures, and karst fissures form the downward infiltration channels for groundwater. Therefore, in this technical solution, by sealing the mine, the groundwater runoff entering the mine pit is intercepted to the greatest extent.

[0060] Therefore, in this technical solution, first, a surface water drainage channel is designed to lead the surface water out of the mining area, minimizing the replenishment of surface water to the mine; second, by sealing the mine, the groundwater runoff entering the mine pit is blocked to the greatest extent; finally, precipitation diversion wells are designed to introduce the groundwater infiltrating into the upper aquifer 5 into the wells, thus effectively controlling the water inrush source of the mine and solving the problem of mine water inrush from the source.

[0061] This technical solution can control the pollution of the mining area from the source, that is, it can realize the comprehensive renovation of the polluted environment left over from history in the region, and it also belongs to the related technology of regional water pollution control. It can directly reduce the heavy metal pollution in the water body and soil of the mining area, and has a positive effect on solving the problems left over from history and improving the regional ecological environment.

[0062] For the implementation of this plan, regional hydrogeological surveys need to be carried out to understand the problems of precipitation and water quality changes. This plan solves the problem of mine water pollution through seepage precipitation control and surface drainage around the mine, with relatively small investment and short construction period.

[0063] Example 2:

[0064] This example is optimized based on Example 1 above.

[0065] To achieve a better sealing effect, the sealing length of the mine can extend 10m inward from the mine entrance, and the specific extension length is determined according to the survey results.

[0066] Example 3:

[0067] This example is optimized based on Example 1 above.

[0068] To divert the precipitation near the mine into the wells over a larger area and reduce the water infiltration into the mine or the ore layer 6, the number of precipitation diversion wells shall not be less than the number of mines in the mining area, and the positions of the precipitation diversion wells are distributed near the mine entrance or along the extension direction of the main mine tunnel.

[0069] Example 4:

[0070] This example is optimized based on Example 3 above.

[0071] To improve the precipitation diversion effect and realize the diversion of groundwater in a timely manner, three precipitation diversion wells are respectively set near the mine entrance and along the extension direction of the main mine tunnel.

[0072] Embodiment 5:

[0073] This embodiment is optimized based on the above-mentioned embodiment 4.

[0074] For each mine, in order to minimize groundwater pollution, the spacing between adjacent precipitation drainage wells can be 80m-150m, which is determined based on hydrogeological tests.

[0075] Embodiment 6:

[0076] This embodiment is optimized based on the above-mentioned embodiment 1.

[0077] In order to prevent groundwater from entering the mine from the collapsed area and causing mine water gushing, if there is a collapsed area in the mine, the collapsed area in the mine should be filled and the silt should be cleaned.

[0078] Embodiment 7:

[0079] This embodiment is optimized based on the above-mentioned embodiment 6.

[0080] Clean the sludge in the original drainage ditch in the mining area, and then transport it away or use it to fill the collapsed area. Cleaning the sludge in the original drainage ditch can reduce the overflow of mining wastewater and reduce its impact on the surrounding soil.

[0081] Embodiment 8:

[0082] This embodiment is optimized based on the above-mentioned embodiment 1.

[0083] In order to improve the drainage effect and service life of the surface water drainage channel, the inner wall of the surface water drainage channel is cast in concrete, and the cross-section of the surface water drainage channel is a rectangular section.

[0084] Embodiment 9:

[0085] This embodiment is optimized based on the above-mentioned embodiment 1.

[0086] In order to remove the contaminated soil layers in the mining area as much as possible and restore the ecological environment of the mining area to a certain extent, it also includes removing the contaminated soil layers on the surface of the mining area and centrally landfilling the removed soil layers.

[0087] Embodiment 10:

[0088] This embodiment is optimized based on the above-mentioned embodiment 1.

[0089] In order to better seal the mine, curtain grouting is performed in the fissure karst development zone during the mine sealing process to seal the groundwater runoff channel.

[0090] In the above embodiments, the optimized design of the precipitation drainage well is as follows:

[0091] In order to effectively isolate the ore layer 6, the middle isolation pipe 3 is formed by sealing with concrete to isolate the ore layer 6. To improve the isolation effect and ensure the structural strength of the well pipe, the middle isolation pipe 3 may also include a steel pipe and a concrete pipe wrapped outside the steel pipe.

[0092] To improve the installation efficiency of the well pipe and ensure the water permeability of the upper water-permeable pipe 2 and the lower water-permeable pipe 4, both the upper water-permeable pipe 2 and the lower water-permeable pipe 4 are slotted pipes, and the outer diameter of the slotted pipe is adapted to the inner diameter of the well hole 1.

[0093] To seal the wellhead, a reinforced concrete cover plate 8 is provided at the wellhead of the well hole 1, and a backfill soil layer 11 is covered on the reinforced concrete cover plate 8.

[0094] To achieve a better drainage effect and ensure the drainage flow, and at the same time to improve the structural strength of the wellhead, the diameter of the well hole 1 is 180 mm. A wellhead hole 9 is opened at the wellhead of the well hole 1. The depth of the wellhead hole 9 is 200 mm, the diameter of the wellhead hole 9 is 250 mm. A stabilizing platform 10 is formed by pouring concrete in the wellhead hole 9, and the reinforced concrete cover plate 8 is arranged on the stabilizing platform 10. To enable the depth of the precipitation drainage well to extend into the Maokou Formation aquifer 7, the depth of the well hole 1 is 500 m - 700 m.

[0095] In this technical solution, the groundwater above the ore layer 6 is drained and infiltrated into the Maokou Formation aquifer 7. The designed depth of the precipitation drainage well is 500 - 700 m. The actual depth of the precipitation drainage well may vary during the construction stage. For example, it can be 650 m, and its actual depth is determined by the geological conditions during construction.

[0096] To prevent external leakage of the wellhead, the thickness of the backfill soil layer 11 is 20 cm. To improve the structural strength of the reinforced concrete cover plate 8, the thickness of the reinforced concrete cover plate 8 is 10 cm. To facilitate the operation of the reinforced concrete cover plate 8, a cover plate lifting handle 12 made of steel bars is provided on the reinforced concrete cover plate 8.

[0097] The precipitation drainage well is tested in the mining area. The test process and test data are as follows:

[0098] As Figure 9 shown, a total of seven precipitation drainage test wells are arranged at the entrances of KJ01 - KJ06 mine shafts and on the left side of KJ01 mine shaft, as shown in Table 1:

[0099] Table 1 Statistical table of precipitation test wells

[0100]

[0101]

[0102] Through the implementation of test wells, the water level of SYJ01 test well dropped to 10.50 meters below the ground surface, and the water level of SYJ02 test well dropped to 90.00 meters below the ground surface. When measuring the water level of the test dewatering diversion well SYJ03 with a 200m sounding line, a stable water level could not be measured. Therefore, it was determined that its water level was greater than 200m. The water level of SYJ04 test well dropped to 96 meters below the ground surface, the water level of SYJ05 test well dropped to 39.00 meters below the ground surface, and the water level of SYJ06 test well dropped to 2.6 meters below the ground surface. Among them, the test dewatering diversion well SYJ11 could not measure the water level due to a hole collapse at 20m. Therefore, it was determined that its water level was greater than 20m.

[0103] Through the test of dewatering diversion wells, it was found that the hydraulic connection of groundwater was poor and the permeability of the ore layer was good. After implementing cement sealing and isolation on the ore layer, harmful minerals could be effectively blocked. The dewatering diversion effect was good, and there was no surface water flow at the mine openings of KJ01, KJ02, and KJ03 mines.

[0104] Water samples were taken from a depth of 10 meters in KJ06 well for water quality analysis. The analysis results showed that all indicators met the standards. Then, surface water near the mine cave was taken for water quality analysis, and its indicators were close to those of the well water. The water quality conditions before and after the layout of the dewatering diversion wells are shown in Tables 2 and 3.

[0105] Table 2 Current water quality table before dewatering

[0106]

[0107]

[0108] Table 3 Current water quality table after dewatering

[0109]

[0110] Through engineering investigation and water quality tests after dewatering, it was considered that the plan was feasible. After implementing the dewatering diversion wells, it would not have a great impact on the surrounding geology and would not cause collapses, landslides, mudslides, etc.

[0111] The mine water inrush situation after the implementation of the test wells:

[0112] As shown in Table 4, seven test wells SYJ01, SYJ11, SYJ02, SYJ03, SYJ04, SYJ05, and SYJ06 were respectively implemented near mine shafts KJ01, KJ02, KJ03, KJ04, KJ05, and KJ06. After the test wells were completed, compared with the mine shaft water inrush situation during the same period, there was no longer water inrush in KJ02, KJ03, and KJ04, and the water inrush in KJ01, KJ05, and KJ06 decreased significantly and continuously. KJ08, KJ09, and KJ10 are about 600 m away from the nearest precipitation drainage well, which is a relatively long distance. Therefore, the change in their water inrush was not affected by the precipitation drainage well compared with the same period.

[0113] Table 4 Water Inrush Situation of Each Mine Shaft Before the Implementation of the Test Well

[0114]

[0115] As can be seen from Table 4, the current water inrush of each mine shaft has significantly decreased after the implementation of the test well. It should be noted that no precipitation test well was specifically arranged near mine shaft KJ07, but its water inrush also decreased significantly because mine shaft KJ07 in the test mining area is located downstream of KJ01 - KJ06. Therefore, when the water inrush in KJ01 - KJ06 decreased significantly, the water inrush in KJ07 also decreased significantly.

[0116] The following is an explanation of the precipitation drainage volume of the precipitation drainage test well built in the mining area:

[0117] According to the "Geotechnical Engineering Test and Monitoring Manual", the following formula can be obtained to calculate the flow rate of the precipitation drainage well.

[0118] Q = kAH = 591.7 (t / d)

[0119] In the formula:

[0120] k - The permeability parameter of the test soil layer is taken as 0.139 m / d, and this data is from the regional hydrogeological data;

[0121] Q - The water diversion flow rate (t / d); H - The water head of the aquifer (cm).

[0122]

[0123] In the formula: L - The length of the slotted pipe in the aquifer of the precipitation drainage well (m);

[0124] m - Looked up from the "Geotechnical Engineering Test and Monitoring Manual" Figure 4 .14 - 9. Assuming that the vertical and horizontal permeability coefficients are equal, m is taken as 1;

[0125] r - The radius of the wellbore of the precipitation drainage well.

[0126] Calculation shows that the seepage reduction flow of each test precipitation drainage well is greater than 520 m 3 / d, and the precipitation influence radius of the test precipitation drainage well is 50 m - 100 m. According to the precipitation drainage influence radius and in accordance with the layout principle of precipitation drainage wells, the precipitation drainage wells are arranged.

[0127] The optimized design of the surface water drainage channel is as follows:

[0128] The cross-sectional area of the upstream surface water drainage channel is 0.4 m * 0.4 m. If there is a drainage ditch in the mining area, a downstream surface water drainage channel with a cross-sectional area of 0.4 m × 0.8 m is designed downstream of the original drainage ditch or the newly built upstream surface drainage channel. The downstream surface water drainage channel is connected to the downstream waterway to ensure that the water passing requirement can be met.

[0129] The surface water drainage channel is required to be provided with a telescopic joint every 10 m - 15 m. At the slope change of the bottom slope, large changes in the foundation, and the stepped part of different structures, settlement joints need to be provided. The joint width is 20 - 30 mm, and a 653 water stop belt is used for water stop, and the joint is filled with asphalt wood board; the design flood of the drainage channel takes P = 3.33%, and the check flood is calculated according to P = 1%.

[0130] The requirements for surface pollutant cleaning are as follows:

[0131] In the case where the mine in the mining area has been flooded for many years, it is necessary to remove the polluted soil layer, manually dig it out, and then landfill it centrally.

[0132] After the construction is completed according to this technical solution, it is necessary to monitor the river channel, mainly monitoring the river channel flow and water quality. The water volume monitoring can adopt two methods: automatic monitoring and manual monitoring.

[0133] Precautions for the construction of precipitation drainage wells are as follows:

[0134] It should be noted that during the construction process, the XY-5 type core drill and the SPS-600 type hydrogeological well drill can be used for the construction of the precipitation drainage well. The precipitation drainage well is drilled in a rotary manner and cored throughout the process. During the drilling process, the round-trip footage, the length of the core taken out, the drill dropping, the water leakage, and the position of a large amount of loss of the flushing fluid are recorded in detail, and a relatively comprehensive description is made of the depth and development status of the fractures and karst in the core taken out. Every 50 m of drilling, diameter change, and final hole completion, the drilling depth correction and deviation measurement are carried out, and problems are corrected in time.

[0135] For better carrying of rock powder and preventing core blockage during Quaternary drilling, an internally and externally inserted bit with relatively large internal and external cutting edges and bottom cutting edges can be selected. To avoid water blockage and mud sticking during drilling, the drilling pressure should be controlled at 4 - 5 kN, and it changes to 8 - 10 kN after entering the rock. According to the geological conditions of the mining area, the drillability of the rock is grade 4 - 5, the rotational speed of the bit can be 200 - 300 r / min. To ensure that rock debris particles are promptly carried to the surface, the upward flow velocity of the flushing fluid should be greater than 0.30 m / s, so a pump discharge of 80 - 120 L / min is adopted.

[0136] The strata in the mining area are mainly medium-hard and medium-abrasive rocks. To increase the drilling speed and the service life of the bit, an impregnated diamond bit with a diamond grit size of 46 - 60 mesh, a diamond concentration of 80 - 120%, and a matrix hardness of 35 - 40 can be used for drilling. The following points should be noted during drilling: The bits should be used in groups in sequence. The diameter of the reamer should be 0.3 - 0.5 mm larger than the outer diameter of the bit. The free inner diameter of the catch spring should be 0.3 - 0.4 mm smaller than the inner diameter of the bit. The diameters of the bit and the drill pipe should be as close as possible to ensure the stable operation of the bit at the bottom of the hole.

[0137] Under normal circumstances, the resistance losses at the pipeline system, drill string, and bit are about 0.8 MPa, and the resistance loss per 100 meters of drill pipe is about 0.2 MPa. During drilling, a slight increase or decrease in the pump pressure may indicate a change in formation. Attention should be paid to the footage and the sound of the drill string. If necessary, the drilling parameters can be adjusted to prevent core blockage. If the drilling speed suddenly decreases or there is no footage during drilling, and the pump pressure surges, the drill string should be quickly lifted off the bottom of the hole to prevent a burn - out accident. Therefore, during drilling, the change of pump pressure must be closely observed at all times. To increase the drilling speed, a higher rotational speed can be adopted. To reduce the abnormal wear of diamond bits, vibration reduction work should be done, and the operation must be stable. For this purpose, a reasonable drill string configuration should be used, and a lubricating flushing fluid should be used. During drilling, pay attention to observing the pump pressure gauge, ammeter, footage, and return water conditions to promptly discover problems and lift the drill for treatment. When the formation conditions permit, try to use clean water with a lubricant as the flushing fluid. To strengthen the purification of the flushing fluid and improve its quality, the length of the flushing fluid circulation tank is generally not less than 15 m, and there are at least 2 settling tanks. The slag should be cleared and the flushing fluid should be replaced in a timely manner. Reasonably control the hoisting and lowering speeds of the drill string to reduce the vibration caused by the drill string during lifting and lowering, especially when drilling in complex strata, the hoisting and lowering speeds should be slowed down.

[0138] The foundation should be stable, the base table should be level, and the centers of the vertical axis, the front edge of the crown block, and the center of the borehole design should be in a straight line; the active drill pipe should not be too long and should be fixed at the center of the chuck, and the hole collar pipe should be installed correctly and firmly; when changing the hole diameter, a guide should be used. After the small-diameter core barrel has completely entered the small-diameter hole, the upper large-diameter guide core barrel can be removed; use drill tools with good rigidity, long and straight. Add 1-2 sets of outer pipes with reamers to the upper part of the wireline coring drill tools to ensure the verticality of the drill tools; when drilling in strongly deviated strata, a drilling procedure with reduced pressure, medium and low rotational speed, and appropriate flushing fluid volume should be used; keep the drill pipe in a straightened state, reduce the deflection of the drill pipe, and improve the stability of the drill tools.

[0139] This technical solution adopts the process of "groundwater source diversion control, pollutant isolation, and sludge centralized disposal". Conduct experiments with 1-2 wells. Through the experiments of 1-2 wells, it is proved that the treatment effect is good.

[0140] The design concept of this technical solution: "groundwater source diversion control, key pollutant isolation, and sludge centralized treatment".

[0141] Groundwater source diversion control: Divert the groundwater in the aquifer above the ore layer and the surrounding recharge areas into another aquifer underground through the precipitation diversion well to prevent groundwater from seeping into the ore layer.

[0142] Key pollutant isolation: Use cement to seal the ore layer section and the upper and lower contact zones of the precipitation diversion well to prevent groundwater from mixing with the ore body to generate polluted water.

[0143] Sludge centralized treatment: Remove the sludge in the mine cave and on the surface for centralized treatment.

[0144] Such as Figure 10 、 Figure 11 As shown, the precipitation diversion well diverts the water above the ore layer or the groundwater about to enter the ore layer into the well in advance through the infiltration pipe of the precipitation diversion well. The groundwater source well pipe in the well infiltrates downward into the lower part and flows out of the precipitation well along the lower infiltration pipe and into the infiltration water layer (i.e., the lower aquifer). The ore layer section is permanently sealed with cement to prevent groundwater from flowing in the ore layer. After precipitation diversion, a groundwater depression funnel is formed in the mine cave area, and the groundwater level elevation is lower than the mine cave floor, and no sewage will flow out.

[0145] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for treating mine wastewater, characterized in that, It includes the following steps: Build surface water drainage channels in the mining area that are connected to each mine. The surface water drainage channels are connected to the downstream watercourse to intercept and divert rainwater, reducing the replenishment of surface water to the mine; Seal all the mines in the mining area to intercept the groundwater runoff entering the mine pit; Install precipitation drainage wells near the mines in the mining area. The precipitation drainage wells include well holes and well pipes. The well holes sequentially pass through the upper aquifer and the ore layer and extend into the lower aquifer below the ore layer. A well pipe is provided in the well hole. The well pipe includes an upper permeable pipe, a middle isolation pipe, and a lower permeable pipe that are sequentially connected from top to bottom. The upper permeable pipe is located above the ore layer, the lower permeable pipe is located below the ore layer, and the middle isolation pipe is used to isolate the ore layer.

2. The method for treating mine wastewater according to claim 1, wherein: The number of the precipitation drainage wells is not less than the number of mines in the mining area, and the positions of the precipitation drainage wells are distributed near the mine entrance or in the extension direction of the main mine tunnel.

3. The method for treating mine wastewater according to claim 2, wherein: Three precipitation drainage wells are respectively arranged in the extension direction near the mine entrance and the main mine tunnel.

4. A method for treating mine wastewater according to claim 1, characterized in that: If there is a collapse area in the mine, fill the collapse area in the mine and clean up the sludge.

5. The method for treating mine wastewater according to claim 4, characterized in that: Clean up the sludge in the original drainage ditch in the mining area, and transport the cleaned sludge away or use it to fill the collapse area.

6. A method for treating mine wastewater according to claim 1, characterized in that: The inner wall of the surface water drainage channel is cast with concrete, and the cross-section of the surface water drainage channel is a rectangular section.

7. A method for treating mine wastewater according to claim 1, characterized in that: It also includes removing the polluted soil layer on the surface of the mining area.

8. A method for treating mine wastewater according to claim 1, characterized in that: During the process of sealing the mine, curtain grouting is carried out on the fracture karst development zone to block the groundwater runoff channel.

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