Coal mine wastewater natural-ecological treatment structure and multistage purification method

Abstract

The application discloses a kind of coal mine wastewater natural ecological treatment structure and multistage purification method, and is applicable to the ecological restoration and resource utilization of wastewater of historical abandoned coal mine, high-sulfur coal mining area. Full use of the purification mechanism of natural ecological system, through the synergistic effect of physical, chemical and biological effects, the deep purification of coal mine wastewater is realized. Compared with general water purification structure, the application has the advantages of strong pertinence, high treatment efficiency, ecological environment friendly and the like. At the same time, through reasonable size design and plant configuration, the stability and reliability of the treatment system are ensured.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection engineering technology, specifically relating to a natural ecological treatment structure and multi-stage purification method for coal mine wastewater. Background Technology

[0002] Coal mine wastewater (especially acidic coal mine wastewater) is a highly polluted water body formed by the oxidation of sulfides (such as pyrite FeS2) during coal mining. Its main characteristics are strong acidity (pH=1-3) and high levels of heavy metals (Fe2+). 2+ / Fe 3+ Pb 2+ Cd 2+ Mn, etc.), high sulfate (SO4) 2- Furthermore, due to the lack of effective restoration, abandoned coal mines left over from the past are prone to generating large amounts of leaching wastewater during heavy rains, which are directly discharged into rivers and lakes, causing serious ecological pollution (such as water acidification, heavy metal enrichment, and biological death).

[0003] The existing technology has the following shortcomings: First, traditional treatment processes (such as neutralizing agents + membrane separation) have high construction and operation costs; second, it has poor treatment effect on mixed rainwater and sewage (large fluctuations in water volume and complex pollutant composition), making it difficult to adapt to the disorderly discharge scenario of abandoned coal mines; third, industrialized processes damage the natural landscape and are out of touch with the goal of ecological restoration of mining areas; and fourth, it has a single function, focusing only on water purification and not taking into account ecological restoration (such as biodiversity restoration and habitat construction).

[0004] Patent CN116161801A discloses a treatment device, system, and method for acidic coal mine wastewater. It effectively removes (or similar) metal ions from the wastewater and reduces water acidity, increasing pH levels and thus improving water quality. However, it produces a large amount of sludge and has poor eco-friendliness. Patent CN112079444B discloses a simulated natural wetland system and its purification method. This system includes artificial ecological channels, artificial plant ponds, and artificial substrate ponds. While it utilizes plant-microorganism synergistic purification, it is only suitable for rural domestic sewage or agricultural non-point source pollution (low pollutant concentration and stable water volume). It cannot address the high acidity and heavy metal content of coal mine wastewater and is prone to plant death. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in current coal mine wastewater treatment technologies, such as large consumption of chemical reagents, low heavy metal removal efficiency, high energy consumption, poor adaptability to water volume, and insufficient environmental friendliness.

[0006] The technical solution of this invention: A natural ecological treatment structure for coal mine wastewater, comprising five ecological purification units connected sequentially by pipelines, including... Level 1 ecological sedimentation pond: The water flow in the pond is horizontal and S-shaped, and an intercepting and adsorption mesh is installed in the middle of the pond; Level 2 forced oxidation pond: An ecological filter dam is installed at the inlet end, and microporous aerators and microbial attachment substrates are alternately arranged at the bottom of the pond. An ecological floating bed is laid on the surface of the pond. Level 3 acid regulation pond: The water flow in the pond is vertical S-shaped. The pond is filled with lime and natural manganese sand filter media. Emergent plants are planted in the area filled with natural manganese sand filter media. Level 4 deep purification pond: The water flow in the pond is horizontal S-shaped. The bottom of the pond is filled with a mixture of hydroxyapatite and zeolite from bottom to top. Emergent plants are planted on top of the zeolite mixture. Level 5 aquatic plant pond: planted with a variety of plants and stocked with fish and shellfish. The plants include submerged plants, floating-leaved plants and emergent plants.

[0007] Furthermore, the Level 1 ecological sedimentation pond and the Level 4 deep purification pond are equipped with several partition walls perpendicular to the direction of water inflow. One side of each partition wall is fixedly connected to the bank slope, and the other side has a vertical gap. The gaps of adjacent partition walls are staggered to guide the water flow in the pond to form a horizontal S-shaped flow.

[0008] Furthermore, an intercepting and adsorption mesh is installed between the partition walls of the Level 1 ecological sedimentation pond, and submerged plants and floating-leaved plants are planted at the bottom and surface of the pond, respectively. The intercepting and adsorbing mesh includes a polyethylene intercepting and adsorbing mesh with a mesh size of 2mm. The upper part of the polyethylene intercepting and adsorbing mesh is provided with floats at equal intervals, and the lower part is provided with a gabion counterweight. The gabion counterweight is filled with crushed stones.

[0009] Furthermore, the ecological filter dam is framed by two rows of pine piles driven into the bottom of the pond. The space between the pine piles is filled from the inside out with medium-coarse sand with a particle size of 2-4 mm and pebbles with a particle size of 5-10 mm. The outer perimeter of the pine piles is reinforced with gabion cages. The gap between the pine piles and the gabion cages is filled with geotextile. Emergent plants are planted on the top of the ecological filter dam. The microbial attachment substrate includes a fiber central rope, around which a three-dimensional elastic filler is fixed, and a float and a counterweight stone are respectively connected to the upper and lower ends of the fiber central rope.

[0010] Furthermore, in the three-stage acidic conditioning pond, three partition walls are set perpendicular to the direction of incoming water; among them, the bottom of the first and third partition walls are left with water flow channels between them and the bottom of the pond, and the second partition wall is embedded in the bottom of the pond, with its top elevation lower than that of the first partition wall, so as to guide the water flow to form a vertical S-shaped flow. The lower layer of the space within the first partition wall is filled with natural manganese sand filter media, and the upper layer is filled with lime. In the third-level acidic conditioning pond (C), except for the area of ​​the first partition wall, the other areas are covered with natural manganese sand filter media with a particle size of 0.8 to 1.5 mm.

[0011] Furthermore, the first-stage ecological sedimentation pond draws water through a concrete-cast No. 1 water collection channel; the effluent from the first-stage ecological sedimentation pond enters the second-stage forced oxidation pond via the ecological filter dam; the effluent from the second-stage forced oxidation pond enters the third-stage acid regulation pond via the No. 2 water collection channel and the No. 3 water distribution channel; the effluent from the third-stage acid regulation pond enters the fourth-stage deep purification pond via the No. 3 water collection channel and the No. 4 water distribution channel; and the effluent from the fourth-stage deep purification pond enters the fifth-stage aquatic plant pond via the No. 4 water collection channel.

[0012] Furthermore, the coal mine wastewater simulated natural ecological treatment structure is a wide and shallow structure, and the bottom of all its purification units is treated with HDPE geomembrane combined with a 30mm thick clay layer for seepage prevention.

[0013] A multi-stage purification method for coal mine wastewater based on a simulated natural ecological treatment structure includes the following steps: Step 1: Wastewater enters the primary ecological sedimentation pond, where large suspended solids are removed by gravity sedimentation, the biodegradability of the wastewater is improved by hydrolysis and acidification, and some organic matter is removed by adsorption. Step 2: Wastewater enters the secondary forced oxidation pond, where it is aerated by microporous aerators to remove Fe. 2+ Oxidized to Fe 3+ And remove some of the chemical oxygen demand (COD) and ammonia nitrogen (NH3-N); Step 3: Wastewater enters a three-stage acid-conditioning pond, where the pH is adjusted to a moderately alkaline range through lime neutralization, and residual Fe is catalytically oxidized using natural manganese sand filter media. 2+ and Mn 2+ This promotes the precipitation of heavy metal hydroxides and removes some sulfates; Step 4: Wastewater enters a four-stage deep purification pond, where heavy metal ions and residual nitrogen and phosphorus pollutants are deeply removed through the ion exchange of hydroxyapatite and the adsorption of zeolite mixed packing material, combined with the synergistic effect of plants and microorganisms. Step 5: Wastewater enters a 5-stage aquatic plant pond, which enhances nitrogen and phosphorus removal and provides habitat for aquatic organisms by creating a diverse aquatic plant and animal ecosystem.

[0014] Furthermore, the primary ecological sedimentation pond (A) undergoes a hydrolysis and acidification reaction, specifically, Fe occurs in the second-stage forced oxidation pond (B). 2+Oxidation reaction, specifically, The third-level acidic conditioning pond (C) undergoes neutralization and heavy metal precipitation reactions, specifically as follows: Ion exchange reactions occur in the fourth-stage deep purification pond (D).

[0015] The fifth-level aquatic plant pond (E) undergoes ammonium ion nitrification. In the aquatic plant pond, ammonia nitrogen (NH3-N) is converted into nitrate (NO3-N) by nitrifying bacteria. - Total nitrogen removal is achieved by combining it with the denitrification process.

[0016] Furthermore, the effluent quality after treatment by the five-stage aquatic plant pond meets the following indicators: pH = 6.8–7.2, SS ≤ 18 mg / L, Fe 2+ <0.5 mg / L, Pb 2+ <0.05mg / L, COD≤32mg / L, NH3-N<3mg / L, these indicators are better than the limits required by the "Emission Standard of Pollutants for Coal Industry" (GB20426-2006). Beneficial effects of the present invention 1. A natural, multi-stage S-shaped flow design, using alternating gaps in the partition walls, guides water flow in a horizontal S-shape in the ecological sedimentation pond and deep purification pond, reducing flow velocity and extending hydraulic retention time (HRT = 24–48 h), thus enhancing gravity settling and plant-filler adsorption efficiency. The acidic conditioning pond employs a vertical S-shaped flow, with gaps / embedded sections at the bottom of the partition walls to promote vertical mixing and prevent short-circuiting. Compared to traditional straight-flow processes, SS removal rate is increased by 30%, and heavy metal (Pb) removal rate is significantly reduced. 2+ Cd 2+ The removal rate was increased by 25%.

[0017] 2. Synergistic purification using natural materials and functional fillers: The ecological sedimentation pond uses a PE mesh (2mm mesh) to intercept fine particles, replacing traditional bar screens (to avoid clogging); the acidic conditioning pond is lined with natural manganese sand filter media (0.8-1.5mm particle size), utilizing the catalytic oxidation of MnO2 to remove Fe... 2+ Converted to Fe 3+ (No additional oxidant required); the deep purification pond is filled with a mixture of hydroxyapatite and zeolite (volume ratio 1:1) to fix heavy metals (Pb) through ion exchange. 2+ Cd 2+ ) and sulfate (SO4) 2- Compared to chemical methods, the amount of chemicals added is reduced by 80%, and the sludge production is reduced by 60%.

[0018] 3. The system features a combined sewer system design, with an overall "wide and shallow" layout (pond width 10-20m, water depth 1.0-3.0m). It is equipped with four collection ponds (No. 1, No. 2, No. 3, and No. 4) to accommodate large volumes of wastewater during the rainy season, while allowing for slow release and treatment through ecological filter dams during the dry season. Compared to traditional wastewater treatment plants that can only handle stable flow rates, this system significantly improves the combined sewer system's treatment capacity, ensuring consistently high-quality effluent.

[0019] 4. Ecological landscaping and biodiversity creation: The entire system is planted with emergent, floating-leaved, and submerged plants, and fish (silver carp, bighead carp) and shellfish (river mussels, snails) are released to create a complex food chain of "plant-microorganism-animal" (e.g., "algae → rotifers → silver carp" and "debris → bacteria → benthic animals"), taking into account both water purification and ecological restoration. The system's biodiversity index is >2.5, providing habitats for birds and fish, and the landscape effect is close to that of natural wetlands. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments 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.

[0021] Figure 1 This is a cross-sectional schematic diagram of the simulated natural ecological treatment structure and method for coal mine wastewater in this invention; Figure 2 This is a schematic diagram of the simulated natural ecological treatment structure and method for coal mine wastewater in this invention. Figure 3 This is a schematic diagram of the interception and adsorption membrane structure in this invention; Figure 4 This is a schematic diagram of the ecological filter dam structure in this invention; Figure 5 This is a schematic diagram of the microbial attachment substrate structure in this invention; Attached diagram labels: 1-Coal mine wastewater and runoff non-point source, 2-Pipeline, 3-No. 1 collection channel, 4-Water surface, 5-Compacted soil, 6-HDPE geomembrane, 7-Partition wall, 8-Interception and adsorption mesh, 9-Submerged plants, 10-Floating-leaved plants, 11-Emerging plants, 12-Ecological filter dam, 13-Microporous aerator, 14-Microbial attachment substrate, 15-Ecological floating bed, 16-No. 2 collection channel, 17-No. 3 collection channel, 18-Lime, 19-Natural manganese sand filter media, 20-No. 3 collection pool, 21- No. 4 water distribution tank, 22-hydroxyapatite, 23-zeolite filler, 24-No. 4 water collection channel, 26-float, 27-polyethylene interception and adsorption mesh, 28-counterweight gabion, 29-counterweight stones, 30-fiber central rope, 31-three-dimensional elastic filler, 32-gabion gabion, 33-geotextile, 34-pine piles, 35-medium coarse sand, 36-pebbles, A-1 grade ecological sedimentation pond, B-2 grade forced oxidation pond, C-2 grade forced oxidation pond, D-4 grade deep purification pond, E-5 grade aquatic plant pond. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should not be construed that the scope of the subject matter of the present invention is limited to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0023] The purpose of this invention is to maximize the removal of pollutants through natural physical, chemical, and biological processes by constructing a multi-stage natural purification system, thereby reducing or avoiding the excessive use of chemical reagents. A specially designed acid-conditioning pond and a deep purification pond utilize the packing properties of natural manganese sand, hydroxyapatite, and zeolite to effectively remove heavy metals from wastewater. The entire treatment system operates based on natural forces (such as gravity flow and microbial action), reducing external forces. Microporous aeration is primarily powered by solar panels, lowering energy consumption and operation and maintenance costs. Through a structure consisting of an ecological sedimentation pond (ecological filter dam), a forced oxidation pond, an acid-conditioning pond, a deep purification pond, and an aquatic plant pond, a diverse ecosystem is constructed, enhancing the system's adaptability to water volume fluctuations, promoting biodiversity, and strengthening the environmental friendliness of the treatment system.

[0024] Reference Figures 1-5A simulated natural ecological treatment structure and multi-stage purification method for coal mine wastewater is disclosed. The treatment structure consists of five interconnected ecological purification units: ecological sedimentation pond A → forced oxidation pond B → acid regulation pond C → deep purification pond D → aquatic plant pond E, accompanied by collection channels and distribution pools. The collection channels include collection channels 1 (3), 2 (16), 3 (17), and 3 (20), and distribution pool 4 (21) and collection channel 4 (24). An ecological filter dam 12 and other auxiliary facilities are also included. Upstream of ecological sedimentation pond A, coal mine wastewater and runoff surface source 1 are connected. The coal mine wastewater and runoff surface source 1 enter collection channel 1 (3) through pipe 2. The water surface 4 of collection channel 1 (3) is covered with compacted soil 5. The entire system's pond bottom uses an HDPF geomembrane 6 combined with a 30mm thick clay impermeable layer. The purification method achieves wastewater purification and ecological restoration through multi-stage flow control, packing adsorption, and plant-microorganism synergistic effects.

[0025] Purification process flow: Coal mine wastewater (non-point source runoff) → No. 1 collection canal (concrete pouring) → Level 1 ecological sedimentation pond (S-shaped flow pattern + mesh membrane interception) → Ecological filter dam (pine piles + sand and gravel) → Level 2 forced oxidation pond (solar aeration + submerged plants) → No. 2 collection canal → No. 3 distribution canal → Level 3 acid regulation pond (lime regulation + natural manganese sand) → No. 3 collection canal → No. 4 distribution canal → Level 4 deep purification pond (hydroxyapatite + zeolite filler + plant purification) → No. 4 collection canal → Level 5 aquatic plant pond (various plants + fish and shellfish) → Clean water reuse (irrigation, landscape water) or discharge.

[0026] The Level 1 ecological sedimentation pond functions to remove large suspended solids (SS) particles through gravity sedimentation, improve biodegradability through hydrolysis and acidification, and remove some organic matter through adsorption. Structural design: Water is drawn into the pond through a concrete-cast No. 1 collection channel 3 (0.8-1.2m wide, 1.2m deep). The pond is divided into five sections vertically to the incoming water direction by four partition walls 7 (3.0m high, 0.5m thick). One side of the partition wall is flush with the bank slope, while the other side has a 0.5-1m vertical gap (the gap positions are for exchange), guiding the water flow in a horizontal S-shaped pattern. An intercepting and adsorption mesh 8 (PE material, 2m mesh) is installed between partition walls #2 and #3. The netting is spaced 1m apart with floats, and the bottom is counterweighted with gabions (filled with gravel). The netting is 0.5m from the water surface and 1.0m from the bottom of the pond. Submerged plants (Vallisneria natans, Hydrilla verticillata) are planted at the bottom, and floating-leaved plants (Water lilies, Water chestnuts) and emergent plants (Reeds, Cattails) are planted at the surface, with a plant coverage rate of 10%-15%. The water depth in the sedimentation area of ​​the ecological sedimentation pond is controlled at 2.5-3.0m, and the water depth in the submerged plant planting area is controlled at 1.0-1.5m.

[0027] The level 2 forced oxidation pond functions to reduce Fe by increasing oxygen levels. 2+ Oxidized to Fe 3+(Promotes sedimentation) and removes some COD and NH3-N. Structural design: An ecological filter dam 12 is installed at the inlet to prevent suspended solids and plant debris from entering the secondary system. The filter dam 12 is fixed by two rows of pine piles (1.0m apart, extending 1.5m into the pool bottom), with medium-coarse sand (2-4mm particle size) and surface pebbles (5-10mm particle size) filling the middle. The outer perimeter is reinforced with a steel gabion (1.0m × 1.0m × 1.5m). Aquatic plants are planted on top of the ecological filter dam. The ecological filter dam 12 receives water treated in the sedimentation tank and transports the treated water to the next treatment unit. The ecological filter dam 12 provides a good water flow channel while allowing aquatic plants and microorganisms to attach and grow. The ecological filter dam 12 is framed by two rows of pine piles 34 driven into the bottom of the pond. The space between the pine piles 34 is filled from the inside out with medium-coarse sand 35 with a particle size of 2-4 mm and pebbles 36 with a particle size of 5-10 mm. The outer perimeter of the pine piles 34 is reinforced with gabion cages 32. The gap between the pine piles 34 and the gabion cages 32 is filled with geotextile 33. Emergent plants 11 are planted on the top of the ecological filter dam 12. The aquatic plants and microorganisms further remove suspended solids and some organic matter through absorption, adsorption and degradation. The application of ecological filter dams increases the diversity of the ecosystem and improves treatment efficiency. The planting of aquatic plants also enhances the aesthetics of the treatment system. The forced oxidation pond has a water depth of 1.0–2.0 m, with a combination of submerged plants (Myriophyllum spicatum, Potamogeton crispus) arranged on the bottom. An ecological floating bed 15 is installed within the pond, and a microbial attachment substrate 14 is placed below the floating bed. The microbial attachment substrate 14 includes a fiber central rope 30, around which three-dimensional elastic filler 31 is fixed. Float balls 26 and counterweight stones 29 are connected to the upper and lower ends of the fiber central rope 30, respectively. Microorganisms attach to the substrate to form a biofilm, removing organic matter and some heavy metals from the wastewater through degradation. A solar-powered microporous aerator 13 (1.5 KW power, aerator head spacing of 2.0 m, bottom aeration) is installed. The effluent enters the No. 3 distribution tank via a No. 2 collection tank 16 (connected by a PVC pipe, 500 mm diameter).

[0028] The three-stage acid-conditioning pond functions to adjust the pH to a slightly alkaline level, using natural manganese sand for catalytic oxidation of Fe. 2+ / Mn 2 +To remove heavy metals and some sulfates. Structural design: Three partition walls are arranged vertically to the water flow direction in the pond. The bottom of the first and third partition walls is left with a 50cm gap. The second partition wall is embedded in the bottom of the pond and its top height is 30cm lower than the first partition wall, guiding the water flow in a vertical S-shape. The lower layer of the first partition wall is filled with natural manganese sand filter material 19 and the upper layer is filled with lime 18 (CaO). Other areas are covered with natural manganese sand filter material 19 (particle size 0.8-1.5mm, filling thickness 1.0-1.5m). Emergent plants (calamus, water onion) are planted on the surface. The roots of the plants form an aerobic zone (nitrification reaction) and the bottom layer forms an anaerobic zone (denitrification reaction). The pond is naturally sloped (slope 1:5) and planted with herbaceous plants (berlebsiella) on the slope to stabilize the soil.

[0029] The 4-stage deep purification pond functions to deeply remove heavy metals and residual nitrogen and phosphorus through ion exchange and synergistic effects of plants and microorganisms. The pond is divided into 5 sections perpendicular to the water inflow direction by 3 partition walls. One side of each partition wall is flush with the bank slope, while the other side has a 0.5–1m vertical gap (the gap positions are for ion exchange, respectively), guiding the water flow in a horizontal S-shaped pattern. The pond bottom is filled with a mixture of hydroxyapatite 22 and zeolite 23 (volume ratio 1:1, filling thickness 1.0–1.2m), and emergent plants (reeds, water chestnuts) are planted above the filler layer. The effluent flows through the No. 4 collection tank 24 (connected by PVC pipe) into the 5-stage aquatic plant pond.

[0030] The Level 5 aquatic plant pond serves to create a diverse aquatic ecosystem, enhance nitrogen and phosphorus removal, and provide habitats for organisms. Structural design: The pond is designed according to the terrain elevation, with a water depth of 1.5–2.5 m. Emergent plants (reeds, cattails), floating-leaved plants (water lilies, water lilies), and submerged plants (Ceratophyllum demersum, Vallisneria natans) are planted, with a plant density ≥ 16 plants / m². 2 ; Filter-feeding fish (silver carp and bighead carp, density 50 fish / acre) and benthic shellfish (river mussels and snails, density 200 kg / acre) are released to form a synergistic purification system of "plant-microorganism-animal"; Ecological revetment (rocks + grass) is set up around the perimeter.

[0031] The chemical reactions in each unit pond are as follows: ① Hydrolysis and acidification reaction (ecological sedimentation pond) ②Fe 2+ Oxidation reaction (forced oxidation pond) ③ Neutralization and heavy metal precipitation reaction (acidic adjustment tank) Neutralizing acidic wastewater (pH increase) generates insoluble CaSO4 precipitate, reducing sulfate concentration.

[0032] Combined with natural manganese sand filter media (MnO2), it catalyzes Fe 2+ Oxidized to Fe3+ This promotes the precipitation of metal hydroxides. Fe 3+ Further hydrolysis generates Fe(OH)3 colloids, which adsorb suspended solids and heavy metal ions. Mn 2+ It can be adsorbed and fixed by hydroxyapatite.

[0033] ④ Ion exchange reaction (deep purification pond) In the deep purification pond, hydroxyapatite (Ca 10 (PO4)6(OH)2) adsorbs heavy metal ions (such as Pb) through ion exchange. 2+ Cd 2+ ), release Ca 2+ Zeolites can fix heavy metals and reduce their biotoxicity by adsorption-desorption.

[0034] ⑤ Ammonium ion nitrification reaction (aquatic plant pond) In aquatic plant ponds, ammonia nitrogen (NH3-N) is converted into nitrate (NO3-N) by nitrifying bacteria. - Total nitrogen removal is achieved by combining the denitrification process (under anoxic conditions).

[0035] Feasibility of plant growth in coal mine wastewater treatment ponds. According to research literature, emergent plants such as reeds, cattails, and water onions show strong adaptability in coal mine wastewater treatment. The net photosynthetic rate and transpiration rate of *Liriope muscari*, water onions, and *Acorus gramineus* in coal mine wastewater were significantly higher than those in the clean water control, indicating that they can adapt to highly polluted environments through photosynthesis. The roots of reeds and cattails can adsorb and fix Pb. 2+ Cd 2+ Heavy metals such as manganese are removed to reduce their toxicity to plant growth. Adjusting the pH to a slightly alkaline level (pH 6–9) by systematically adding lime can alleviate the stress of acidity on plant roots. Ecological sedimentation ponds (2.5–3.0 m) and forced oxidation ponds (1.0–2.0 m) utilize stratified planting (emergent + floating-leaved plants) to adapt to different water depths and prevent root hypoxia. Aquatic plant ponds (1.5–2.5 m) employ a multi-level water level design to provide habitat for fish and benthic organisms, indirectly promoting plant community stability. Natural manganese sand (acid-regulating pond) releases manganese (Mn). 2+As essential trace elements for plants, they promote growth. Hydroxyapatite and zeolite (in the deep purification pond) adsorb heavy metals, reducing the risk of plants absorbing pollutants. Submerged plants (Vallisneria natans, Myriophyllum spicatum) release organic acids through their roots, activating nutrients in the bottom sediment and providing nitrogen and phosphorus supplements for other plants. Based on the structure of this patent (such as pH control and filler optimization) and the selection of plants (reeds, cattails, water onions, etc.), plants in the coal mine wastewater treatment pond can grow healthily and work synergistically with microorganisms and substrates to achieve efficient removal of pollutants.

[0036] Example: A historically abandoned coal mine in Guizhou Province, located in a karst landform area, suffers from severe pollution from acidic wastewater (including rainwater and sewage runoff) due to long-term unregulated mining. The annual rainfall reaches 1200mm, and the wastewater flow during the rainy season can reach as high as 800m³. 3 / h, the water quality is strongly acidic (pH=2.8) and rich in Fe. 2+ (1200mg / L), Pb 2+ The pollution levels were 0.8 mg / L (suspended solids = 2500 mg / L), COD was 350 mg / L, and NH3-N was 25 mg / L, causing serious damage to the surrounding water bodies and ecosystems. To address this issue, the project adopted a 5-stage simulated natural ecological treatment system. After compacting the bottom of the project area, a 6-layer HDPE geomembrane was laid, followed by a 5-layer 0.3m thick clay layer to prevent seepage. Coal mine wastewater 1 flows east-west through a PVC pipe 2 (approximately 300mm in diameter) into collection channel 1, then into an ecological sedimentation pond (60m×25m×2.5m). It passes through a north-south partition wall 7, with 0.5-1m gaps on the north and south sides, creating a horizontal S-shaped flow. A polyethylene interception and adsorption membrane 27 (1.5-2mm mesh) removes over 80% of suspended solids. A small amount of submerged plants 9 (Vallisneria natans, Myriophyllum spicatum) and floating-leaved plants 10 (Hydrocotyle vulgaris, Piper kaempferia) are planted to enhance sedimentation and hydrolysis acidification. The water then flows through an ecological filter dam 12 (10m×25m×3m) into a forced oxidation pond (40m×25m×2.0m). The forced oxidation pond is equipped with four solar-powered microporous aerators 13 (300W each), a microbial attachment substrate 14, and an ecological floating bed 15 to absorb Fe. 2+ Oxidized to Fe 3 +Dissolved oxygen (DO) is increased to above 3 mg / L. Water flows into Collection Tank 2 (16), then through a PVC pipe (approximately 300 mm in diameter) to Distribution Channel 3 (17), and finally into the acidic conditioning pond (50m × 30m × 2.5m). It then flows through a north-south partition wall (7), with 0.5-1m gaps at the top and bottom, creating a vertical S-shaped flow. The upper layer of the first partition wall is filled with lime (18), and the lower layer with natural manganese sand (0.8-1.5 mm particle size). The remaining areas are also filled with natural manganese sand (19), adjusting the pH from 2.8 to 7.0-7.5 to catalyze the precipitation of heavy metal hydroxides. Water then flows into Collection Tank 3 (20), then through a PVC pipe (approximately 300 mm in diameter) to Distribution Channel 4 (21), and finally into the deep purification pond (40m × 30m × 2.0m). The deep purification pond uses a mixture of hydroxyapatite (22) and zeolite (23) (volume ratio 1:1) as filler, adsorbing Pb through ion exchange. 2+ Cd 2+ Heavy metals, combined with emergent plants 11 (reed, cattail, water onion) for further nutrient purification; water flows into No. 4 collection pool 24 and enters the aquatic plant pond (60m×30m×2.5m) through a PVC pipe 2 with a diameter of about 300mm. The aquatic plant pond constructs an "emergent-floating-sinking" complex community (reed, water chestnut, goldfish algae). Silver carp (30 fish / mu), bighead carp (90 fish / mu) and shellfish (200kg / mu) are released. (25) ecological islands are set up to create bird habitats and form a complete food chain to strengthen ecological restoration. After the system is in operation, the effluent water quality is stable and meets the standards, pH=6.8~7.2, SS drops to 18mg / L, Fe 2+ <0.5 mg / L, Pb 2+ <0.05mg / L, COD reduced to 32mg / L, NH3-N <3mg / L, far superior to the "Emission Standard of Pollutants for Coal Industry" (GB20426-2006).

[0037] This invention creates a highly efficient and environmentally friendly natural ecological treatment system for coal mine wastewater. This system fully utilizes the purification mechanisms of natural ecosystems, achieving deep purification of coal mine wastewater through the synergistic effect of physical, chemical, and biological processes. Compared to conventional water purification structures, this invention has significant advantages such as strong targeting, high treatment efficiency, and environmental friendliness. Furthermore, through reasonable size design and plant configuration, the stability and reliability of the treatment system are ensured.

[0038] The foregoing has provided a detailed description of the simulated natural ecological treatment structure and multi-stage purification method for coal mine wastewater provided by this invention. Specific examples have been used to illustrate the structure and working principle of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this invention.

Claims

1. A natural ecological treatment structure for coal mine wastewater, characterized in that: Includes five levels of ecological purification units connected sequentially via pipe (2), including, Level 1 ecological sedimentation pond (A): The water flow in the pond is in a horizontal S-shaped state, and an intercepting and adsorption mesh (8) is set in the middle of the pond. Level 2 forced oxidation pond (B): An ecological filter dam (12) is installed at the water inlet. Microporous aerators (13) and microbial attachment substrates (14) are alternately arranged at the bottom of the pond. An ecological floating bed (15) is laid on the surface of the pond. Level 3 acidic conditioning pond (C): The water flow in the pond is vertical S-shaped. The pond is filled with lime (18) and natural manganese sand filter media (19). Emergent plants (11) are planted in the area filled with natural manganese sand filter media (19). Level 4 deep purification pond (D): The water flow in the pond is in a horizontal S-shaped state. The bottom of the pond is filled with hydroxyapatite (22) and zeolite mixed filler (23) from bottom to top. Emergent plants (11) are planted above the zeolite mixed filler (23). Level 5 Aquatic Plant Pond (E): Plants a variety of plants and releases fish and shellfish. The plants include submerged plants (9), floating-leaved plants (10) and emergent plants (11).

2. The coal mine wastewater simulated natural ecological treatment structure according to claim 1, characterized in that: The Level 1 ecological sedimentation pond (A) and the Level 4 deep purification pond (D) are equipped with several partition walls (7) perpendicular to the direction of water inflow. One side of the partition wall (7) is fixedly connected to the bank slope, and the other side has a vertical gap. The gaps of adjacent partition walls (7) are staggered to guide the water flow in the pond to form a horizontal S-shaped flow.

3. The coal mine wastewater simulated natural ecological treatment structure according to claim 2, characterized in that: An intercepting and adsorption mesh (8) is installed between the partition walls (7) of the Level 1 ecological sedimentation pond (A), and submerged plants (9) and floating-leaved plants (10) are planted in the bottom and surface layers of the pond, respectively. The intercepting and adsorbing mesh (8) includes a polyethylene intercepting and adsorbing mesh (27) with a mesh size of 2 mm. Floats (26) are evenly spaced on the upper part of the polyethylene intercepting and adsorbing mesh (27), and a gabion counterweight (28) is provided on the lower part. The gabion counterweight (28) is filled with crushed stones.

4. The coal mine wastewater simulated natural ecological treatment structure according to claim 1, characterized in that: The ecological filter dam (12) is framed by two rows of pine piles (34) driven into the bottom of the pond. The space between the pine piles (34) is filled from the inside out with medium-coarse sand (35) with a particle size of 2-4 mm and pebbles (36) with a particle size of 5-10 mm. The outer perimeter of the pine piles (34) is reinforced with gabion cages (32). The gap between the pine piles (34) and the gabion cages (32) is filled with geotextile (33). Emergent plants (11) are planted on the top of the ecological filter dam (12). The microbial attachment substrate (14) includes a fiber central rope (30), and three-dimensional elastic filler (31) is fixed around the fiber central rope (30). The upper and lower ends of the fiber central rope (30) are respectively connected to a float (26) and a counterweight stone (29).

5. The coal mine wastewater simulated natural ecological treatment structure according to claim 1, characterized in that: In the three-stage acidic conditioning pond (C), three partition walls (7) are set perpendicular to the direction of incoming water; among them, the bottom of the first and third partition walls are left with water flow channels between them and the bottom of the pond, and the second partition wall is embedded in the bottom of the pond, with its top elevation lower than that of the first partition wall, so as to guide the water flow to form a vertical S-shaped flow. The lower layer of the space inside the first partition wall is filled with natural manganese sand filter material (19), and the upper layer is filled with lime (18). In the third-level acidic conditioning pond (C), except for the area of ​​the first partition wall, natural manganese sand filter material (19) with a particle size of 0.8 to 1.5 mm is laid.

6. The coal mine wastewater simulated natural ecological treatment structure according to claim 1, characterized in that: The first-level ecological sedimentation pond (A) draws water through the No. 1 water collection channel (1) made of concrete; the effluent from the first-level ecological sedimentation pond (A) enters the second-level forced oxidation pond (B) through the ecological filter dam (12); the effluent from the second-level forced oxidation pond (B) enters the third-level acid regulation pond (C) through the No. 2 water collection channel (16) and the No. 3 water distribution channel (17); the effluent from the third-level acid regulation pond (C) enters the fourth-level deep purification pond (D) through the No. 3 water collection channel (20) and the No. 4 water distribution channel (21); the effluent from the fourth-level deep purification pond (D) enters the fifth-level aquatic plant pond (E) through the No. 4 water collection channel (24).

7. The coal mine wastewater simulated natural ecological treatment structure according to claim 1, characterized in that: The coal mine wastewater simulated natural ecological treatment structure is a wide and shallow structure. The bottom of all its purification units is treated with HDPE geomembrane combined with a 30mm thick clay layer for seepage prevention.

8. The multi-stage purification method for coal mine wastewater with a simulated natural ecological treatment structure according to any one of claims 1-7, characterized in that: Includes the following steps, Step 1: Wastewater enters the primary ecological sedimentation pond (A), where large suspended solids (SS) are removed by gravity sedimentation, the biodegradability of the wastewater is improved by hydrolysis and acidification, and some organic matter is removed by adsorption. Step 2: Wastewater enters the secondary forced oxidation pond (B), where it is aerated by a microporous aerator (13) to remove Fe. 2+ Oxidized to Fe 3+ And remove some of the chemical oxygen demand (COD) and ammonia nitrogen (NH3-N). Step 3: Wastewater enters a three-stage acidic conditioning pond (C), where the pH is adjusted to a moderately alkaline range by the neutralization effect of lime (18), and residual Fe is catalytically oxidized by natural manganese sand filter media (19). 2+ and Mn 2+ This promotes the precipitation of heavy metal hydroxides and removes some sulfates; Step 4: Wastewater enters the 4-stage deep purification pond (D), where heavy metal ions and residual nitrogen and phosphorus pollutants are deeply removed through the ion exchange of hydroxyapatite (22) and the adsorption of zeolite mixed packing material (23), combined with the synergistic effect of plants and microorganisms. Step 5: Wastewater enters the Level 5 aquatic plant pond (E), which enhances nitrogen and phosphorus removal and provides habitat for aquatic organisms by creating a diverse aquatic plant and animal ecosystem.

9. The multi-stage purification method for coal mine wastewater with a simulated natural ecological treatment structure according to claim 8, characterized in that: The first-level ecological sedimentation pond (A) undergoes a hydrolysis and acidification reaction, specifically, Fe occurs in the second-stage forced oxidation pond (B). 2+ Oxidation reaction, specifically, The third-level acidic conditioning pond (C) undergoes neutralization and heavy metal precipitation reactions, specifically as follows: The fourth-stage deep purification pond (D) undergoes an ion exchange reaction, specifically, hydroxyapatite (Ca) 10 (PO4)6(OH)2) adsorbs heavy metal ions through ion exchange, releasing Ca 2+ Zeolites can fix heavy metals and reduce their biotoxicity by adsorption-desorption. The fifth-level aquatic plant pond (E) undergoes ammonium ion nitrification. In the aquatic plant pond, ammonia nitrogen (NH3-N) is converted into nitrate (NO3-N) by nitrifying bacteria. - Total nitrogen removal is achieved by combining it with the denitrification process.

10. The multi-stage purification method for coal mine wastewater with a simulated natural ecological treatment structure according to claim 8, characterized in that: The effluent from the five-stage aquatic plant pond (E) treatment met the following criteria: pH = 6.8–7.2, SS ≤ 18 mg / L, Fe... 2+ <0.5 mg / L, Pb 2+ <0.05mg / L, COD≤32mg / L, NH3-N<3mg / L.

Images