In-situ collaborative treatment method for abandoned mine goaf groundwater

Abstract

This invention discloses an in-situ co-treatment method for groundwater in abandoned mine goaf areas, belonging to the field of environmental engineering. The method includes the following steps: Step 1, draining and replenishing groundwater in the goaf area by setting up cofferdams and water diversion channels; Step 2, grouting and sealing the dominant channels for surface water replenishment to the goaf area, carrying out anti-seepage transformation of the seepage sections in the goaf area, and simultaneously constructing surface drainage and water diversion engineering facilities upstream of the seepage sections to reduce the infiltration and replenishment of the goaf area by surface water and atmospheric precipitation; Step 3, constructing a multi-stage continuous alkali production system using abandoned roadways or along the groundwater seepage path in the goaf area. The continuous alkali production system is used to neutralize the acidity of the groundwater in the goaf area and remove sulfates and heavy metals; Step 4, using an anaerobic-aerobic constructed wetland series treatment for the mine tunnel inflow water in the goaf area. This invention reduces the amount of mine water replenishment in goaf areas by 60-75% through source reduction; by constructing a continuous alkali production system and an artificial wetland at the end of abandoned roadways, it can achieve low-cost and sustainable groundwater management, thereby supporting the further improvement of the ecological environment quality in my country's mining areas.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering and relates to an in-situ synergistic treatment method for groundwater in abandoned mine goaf areas. In particular, it relates to an in-situ multi-technology synergistic treatment method based on groundwater drainage, sealing of surface water recharge channels, continuous alkali production system in roadways, and end-of-pipe artificial wetlands. Background Technology

[0002] my country has nearly 100,000 abandoned mines, generating approximately 10 billion tons of acid mine drainage (AMD) annually. The generation of AMD is not only large in volume and widespread but also characterized by its persistence and sudden onset, causing severe regional pollution and posing a significant challenge to my country's overall ecological civilization construction. However, current AMD remediation efforts in my country primarily rely on proactive measures such as "sealing mines + building wastewater treatment plants"—a "short-term emergency + long-term sustainable" approach—lacking a low-cost, sustainable in-situ remediation technology system. Because traditional mining area groundwater pollution remediation models are simplistic, lack systematicity and sustainability, they are no longer sufficient to support further improvements in the ecological environment quality of my country's mining areas. Therefore, conducting research on low-cost, sustainable remediation of AMD in mining areas is a major strategic need for groundwater pollution prevention and control in my country. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for in-situ co-treatment of groundwater in abandoned mine goaf areas.

[0004] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for in-situ co-treatment of groundwater in abandoned mine goaf areas includes the following steps:

[0006] Step 1: Drain and replenish groundwater in the mined-out area by setting up cofferdams and water diversion channels;

[0007] Step 2: Grouting is carried out to seal the dominant channels for surface water to replenish the goaf, and seepage prevention and transformation is carried out in the seepage sections of the goaf. At the same time, surface drainage and water diversion engineering facilities are built upstream of the seepage sections to reduce the infiltration and replenishment of surface water and atmospheric precipitation to the goaf.

[0008] Step 3: Construct a multi-stage continuous alkali production system using abandoned roadways or along the groundwater seepage path in the goaf. The continuous alkali production system is used to neutralize the acidity of the groundwater in the goaf and remove sulfates and heavy metals.

[0009] Step 4: For the water inflow from the mine goaf, an anaerobic-aerobic constructed wetland series treatment method is adopted.

[0010] To optimize the above technical solution, the specific measures also include:

[0011] In step one, the groundwater replenishment to the goaf is achieved by setting up cofferdams and water diversion channels at the main passages that have hydraulic connections with the goaf, so that the groundwater selectively flows around the goaf, thereby reducing the amount of mine water replenished to the goaf.

[0012] The cofferdam material is an acid-resistant cementitious material prepared by mixing alkali slag and cement; the water diversion channel is a water pipe.

[0013] In step two, the specific method for grouting and sealing the dominant channels for surface water recharge in the goaf is as follows: through ground surveys, tracer tests, and geophysical exploration, the dominant channels for surface water recharge in the goaf are determined, and then these dominant channels are grouted and sealed.

[0014] In step three, the continuous alkali production system consists of an organic matrix layer and an attapulgite and alkali slag composite material layer arranged from top to bottom, with the interlayer filled with a mixed bacterial solution of iron-reducing bacteria and sulfate-reducing bacteria.

[0015] The thickness of the organic matrix layer in the continuous alkali production system is 0.3–0.6 m, and the thickness of the composite material layer of attapulgite and alkali slag is 1.0–1.5 m.

[0016] In step four, the anaerobic-aerobic constructed wetland includes an anaerobic constructed wetland and an aerobic constructed wetland. The anaerobic constructed wetland has a water depth > 0.6m and is filled from top to bottom with soil, an organic matrix layer, attapulgite, and an alkaline slag composite material, respectively. The aerobic constructed wetland has a water depth < 0.3m and is filled with attapulgite and an alkaline slag composite material. The planted in the aerobic constructed wetland is cattail.

[0017] The soil thickness of anaerobic constructed wetlands is 0.2m, the organic matrix layer thickness is 0.3-0.6m, and the thickness of the attapulgite and alkali slag composite material is 0.6-1.0m. The thickness of the attapulgite and alkali slag composite material of aerobic constructed wetlands is 0.3-0.6m.

[0018] The preparation method of the attapulgite and alkali residue composite material is as follows: natural attapulgite mineral and alkali residue, a by-product of the ammonia-soda process, are ground separately in a mortar and pestle to pass through a 0.150mm nylon sieve; the ground attapulgite and alkali residue are mixed evenly at a mass ratio of 5:5, and then 7.5% anhydrous sodium carbonate is added as a binder. Deionized water is added at a solid-liquid ratio of 2:1 to 3:1 by mass. The above materials are then repeatedly kneaded into granules, placed in an oven and dried at 105℃ to constant weight. After cooling, the attapulgite is ground in a mortar and pestle and passed through a sieve to form 1.0-1.5cm particles. After aging for 48 hours, the particles are placed in a muffle furnace and calcined at 450℃ for 2 hours. After cooling, the attapulgite and alkali residue composite material is obtained.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention provides a method for in-situ coordinated treatment of groundwater in abandoned mine goaf areas. It involves constructing cofferdams and water diversion channels to drain and replenish groundwater in the goaf areas; grouting and sealing the dominant channels through which surface water replenishes the goaf areas; implementing anti-seepage modifications to seepage areas; and simultaneously establishing surface drainage and water diversion engineering facilities upstream of the seepage zone. A multi-stage continuous alkali production system is constructed using abandoned roadways or along the groundwater seepage path in the goaf areas. For mine shaft inflow water in the goaf areas, an anaerobic-aerobic constructed wetland series treatment method is adopted, achieving low-cost and sustainable treatment of groundwater in abandoned mine areas.

[0021] Specifically:

[0022] 1. By setting up cofferdams and water diversion channels to drain and replenish groundwater in the goaf, the amount of mine water replenishment in the goaf can be reduced; by grouting and sealing the dominant channels for surface water replenishment to the goaf, and by carrying out anti-seepage transformation of the seepage area, and at the same time building surface drainage and water diversion engineering facilities upstream of the seepage section, the infiltration and replenishment of surface water and rainfall to the goaf can be blocked, which can reduce the amount of polluted water in the goaf by 60-75%.

[0023] 2. By utilizing abandoned roadways or constructing multi-stage continuous alkali production systems along the groundwater seepage path in the goaf, polluted water bodies in the goaf can be treated in situ. This not only significantly reduces treatment costs but also reduces the risk of pollution to aquifers and surface water bodies around the goaf.

[0024] 3. Through steps one, two, and three of this invention, the volume and pollution load of mine drainage water are significantly reduced, alleviating the pressure on end-of-pipe treatment. For mine drainage water in goaf areas, an anaerobic-aerobic constructed wetland series treatment method is adopted, resulting in a significant reduction in overall treatment costs. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the steps of the in-situ co-treatment method for groundwater in abandoned mine goaf areas according to the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0027] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0028] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0029] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms “a,” “an,” “an,” “the,” and similar words used in this application do not indicate quantity limitation and may indicate singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or units (elements) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms “connected,” “linked,” “coupled,” and similar words used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms “multiple” / “several” used in this application refer to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can indicate: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following objects are in an "or" relationship. The terms "first," "second," and "third" used in this application are merely to distinguish similar objects and do not represent a specific ordering of the objects.

[0030] like Figure 1 As shown in the figure, this embodiment provides a method for in-situ co-treatment of groundwater in abandoned mine goaf areas, including the following steps:

[0031] Step 1: Through high-precision environmental geological surveys, the stratigraphic position, distribution, geological structure, and lithology, thickness, distribution, and water-bearing capacity of the goaf are determined. The main channels with hydraulic connection to the goaf are identified, and cofferdams and water diversion channels are constructed at each channel entrance to allow groundwater to selectively flow around the goaf. The cofferdam material is an acid-resistant cementitious material prepared from a mixture of alkali slag and cement, with a mass ratio of 90:10; the water diversion channels are water pipes.

[0032] Step Two: Through ground surveys, tracer experiments, and geophysical exploration, the dominant channels for surface water recharge into the mined-out area are identified. These surface channels are then sealed with grout, and seepage prevention modifications are implemented in the seepage areas. Simultaneously, surface drainage and water diversion engineering facilities are constructed upstream of the seepage zones to reduce the infiltration of surface water and precipitation into the mined-out area. The total filling volume for the surface channels is 30,000 m³. 3 The seepage prevention and renovation area is 7000m². 2 The surface drainage and water diversion facilities are 2km long.

[0033] Step 3: Construct a multi-stage continuous alkali production system using abandoned roadways or along the groundwater seepage path in the goaf. The continuous alkali production system covers an area of ​​1200m². 2 From top to bottom, the substrate is filled with an organic matrix layer (0.3–0.6 m), a mixed bacterial solution of iron-reducing bacteria and sulfate-reducing bacteria, and a composite material of attapulgite and alkali slag (1.0–1.5 m).

[0034] Step 4: For the mine drainage water in the goaf, an anaerobic-aerobic constructed wetland series treatment method is adopted, with each wetland covering an area of ​​900m². 2 Anaerobic constructed wetlands have a water depth > 0.6m and are filled from top to bottom with soil (0.2m), an organic matrix layer (0.3-0.6m), and a composite material of attapulgite and alkali slag (0.6-1.0m). Aerobic constructed wetlands have a water depth < 0.3m and are filled with a composite material of attapulgite and alkali slag (0.3-0.6m). The wetland plant is cattail.

[0035] In steps three and four, the attapulgite and alkali slag composite material is prepared as follows: natural attapulgite mineral and alkali slag, a byproduct of the ammonia-soda process, are ground separately in a mortar and pestle until they pass through a 0.150mm nylon sieve. The ground attapulgite and alkali slag are mixed evenly at a mass ratio of 5:5, and then 7.5% anhydrous sodium carbonate (Na2CO3) is added as a binder. Deionized water is then added at a solid-liquid ratio of 2:1 to 3:1. The above materials are then repeatedly kneaded to form granules. After that, they are placed in an oven at 105℃ and dried to constant weight. After cooling, they are ground in a mortar and pestle and passed through a sieve to form 1.0-1.5cm particles. After aging for 48 hours, they are placed in a muffle furnace and calcined at 450℃ for 2 hours. After cooling, the attapulgite-alkali slag composite material is obtained.

[0036] The results show that by implementing step one, "draining and replenishing groundwater in the goaf," and step two, "blocking infiltration and replenishment channels," the source of mine water in the goaf was reduced, potentially decreasing the amount of mine water by up to 75%. By implementing step three, "constructing a multi-stage continuous alkali-producing system in abandoned roadways or along the groundwater seepage path in the goaf," the groundwater quality was significantly improved, reaching the Class III groundwater quality standard, reducing the risk of groundwater pollution diffusion in the goaf. Furthermore, constructing a continuous alkali-producing system using abandoned roadways reduced costs by more than 30% compared to building it on the surface. For mine tunnel water inflow, by implementing step four, "anaerobic-aerobic artificial wetland series treatment," the water quality met the Class III surface water quality standard, achieving end-of-pipe treatment and controlling the risk of pollution diffusion. The in-situ co-treatment method for groundwater in abandoned mine goafs provided by this invention reduces overall treatment costs by more than 40% and improves pollution reduction by more than 30% compared to traditional end-of-pipe treatment methods such as building sewage treatment plants.

[0037] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for in-situ remediation of abandoned mine workings groundwater, characterized in that: Includes the following steps: Step 1: Drain and replenish groundwater in the mined-out area by setting up cofferdams and water diversion channels; Step 2: Grouting is carried out to seal the dominant channels for surface water to replenish the goaf, and seepage prevention and transformation is carried out in the seepage sections of the goaf. At the same time, surface drainage and water diversion engineering facilities are built upstream of the seepage sections to reduce the infiltration and replenishment of surface water and atmospheric precipitation to the goaf. Step 3: Construct a multi-stage continuous alkali production system using abandoned roadways or along the groundwater seepage path in the goaf. The continuous alkali production system is used to neutralize the acidity of the groundwater in the goaf and remove sulfates and heavy metals. Step 4: For the mine drainage water in the goaf, an anaerobic-aerobic constructed wetland series treatment method is adopted; In step one, the groundwater replenishment to the goaf is achieved by setting up cofferdams and water diversion channels at the main channels that have hydraulic connections with the goaf, so that the groundwater selectively flows around the goaf and reduces the amount of mine water replenished to the goaf. The cofferdam material is an acid-resistant cementitious material prepared by mixing alkali slag and cement; the water diversion channel is a water diversion pipe; In step two, the specific method for grouting and sealing the dominant channels for surface water recharge in the goaf is as follows: through ground surveys, tracer tests and geophysical exploration, the dominant channels for surface water recharge in the goaf are determined, and then these dominant channels are grouted and sealed. In step three, the continuous alkali production system consists of an organic matrix layer and an attapulgite and alkali slag composite material layer arranged from top to bottom, with a mixed bacterial solution of iron-reducing bacteria and sulfate-reducing bacteria filling the spaces between the layers. In step four, the anaerobic-aerobic constructed wetland includes an anaerobic constructed wetland and an aerobic constructed wetland. The anaerobic constructed wetland has a water depth >0.6m and is filled from top to bottom with soil, an organic matrix layer, attapulgite, and an alkali slag composite material, respectively. The aerobic constructed wetland has a water depth <0.3m and is filled with attapulgite and alkali slag composite material. The planted in the anaerobic-aerobic constructed wetland is cattail.

2. The method for in-situ co-treatment of groundwater in abandoned mine goaf areas according to claim 1, characterized in that: The thickness of the organic matrix layer in the continuous alkali production system is 0.3–0.6 m, and the thickness of the composite material layer of attapulgite and alkali slag is 1.0–1.5 m.

3. The method for in-situ co-treatment of groundwater in abandoned mine goaf areas according to claim 1, characterized in that: The soil thickness of anaerobic constructed wetlands is 0.2m, the organic matrix layer thickness is 0.3-0.6m, and the thickness of the attapulgite and alkali slag composite material is 0.6-1.0m. The thickness of the attapulgite and alkali slag composite material of aerobic constructed wetlands is 0.3-0.6m.

4. The method for in-situ co-treatment of groundwater in abandoned mine goaf areas according to claim 3, characterized in that: The preparation method of the attapulgite and alkali residue composite material is as follows: natural attapulgite mineral and alkali residue, a by-product of the ammonia-soda process, are ground separately in a mortar and pestle to pass through a 0.150mm nylon sieve; the ground attapulgite and alkali residue are mixed evenly at a mass ratio of 5:5, and then 7.5% anhydrous sodium carbonate is added as a binder. Deionized water is added at a solid-liquid ratio of 2:1 to 3:1 by mass. The above materials are then repeatedly kneaded into granules, placed in an oven and dried at 105℃ to constant weight. After cooling, the attapulgite is ground in a mortar and pestle and passed through a sieve to form 1.0-1.5cm particles. After aging for 48 hours, the particles are placed in a muffle furnace and calcined at 450℃ for 2 hours. After cooling, the attapulgite and alkali residue composite material is obtained.

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