A wastewater treatment device, an acid mine drainage purification system and a treatment method

Abstract

The application discloses a wastewater treatment device, an acid mine drainage purification system and a treatment method, and belongs to the field of wastewater treatment.The device comprises a limestone interception zone, a biochar interception zone, a confluence ditch, a first-stage sedimentation tank, a first-stage adsorption filter dam, a neutralization dam, a second-stage sedimentation tank, a second-stage adsorption filter dam, an anaerobic fermentation tank, a first-stage subsurface flow tank, a second-stage subsurface flow tank and a submerged plant tank which are sequentially connected.The treatment method based on the system comprises the following steps: intercepting the source of surface and shallow soil, preliminarily depositing and adsorbing and filtering the wastewater after the wastewater is collected, performing secondary neutralization and sedimentation treatment on the wastewater, then performing anaerobic fermentation, finally performing wetland purification treatment, and burning and recycling heavy metals from the planted plants.The purification system has the advantages of low investment cost, simple operation, convenient maintenance, low energy consumption, significantly improved water quality and suitability for ecological management of acid mine drainage.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sewage treatment, in particular to a wastewater treatment device, an acid mine drainage purification system and a treatment method. BACKGROUND

[0002] Acid mine wastewater is an acid liquid containing a large amount of sulfate and various heavy metal ions formed by the oxidation reaction of sulfide minerals exposed to the surface, water, and atmosphere, and gradually dissolved. These liquids mainly come from direct wastewater generated by mining, surface runoff wastewater generated by natural rainfall, and underground sewage generated by the seepage of pit and cave water. These acid liquid wastewaters have low organic content, high sulfate concentration, and low pH value, and the pH value is usually less than 3, and some are even less than 2.0. In addition, the wastewater contains a large amount of heavy metal ions such as iron, aluminum, copper, lead, zinc, nickel, and sulfate anions. Untreated acid mine drainage has a great risk to the environment and organisms, especially harmful heavy metals, which can be enriched through the food chain and cause serious harm to human health.

[0003] The traditional process for treating acid mine drainage mainly includes adsorption and neutralization precipitation. The adsorption method uses adsorbent to adsorb soluble metal ions, and this method has high operation cost. The neutralization precipitation method adds alkaline substances to acid mine wastewater to increase the pH value of the wastewater, so that the metal ions are removed in the form of hydroxide precipitation, and this method produces a large amount of sludge containing heavy metals, forming secondary pollution.

[0004] The prior art CN102701545A discloses a system and process for auxiliary treatment of acid mine wastewater using a stepped interception dam, which includes three interception zones. The interception zones are distributed in a natural stepped trapezoidal shape, and the first two interception zones are provided with a limestone layer to adjust the pH value of the wastewater and reduce the solubility of heavy metals in the wastewater. The second interception zone is provided with a biological layer to reduce sulfate ions to sulfur ions, and the sulfur ions and heavy metal ions dissolved in water form sulfide precipitates and settle in the bottom mud. The last interception zone is planted with aquatic plants to filter and adsorb particulate matter in the wastewater with the root system of the aquatic plants, and reduce the concentration of heavy metal pollutants in the water. Although this method simplifies the complexity and difficulty of the existing method, it still needs to perform primary treatment on the acid mine wastewater, and the treatment period is not short in essence. In addition, a large amount of sulfide precipitates are easily accumulated in the last two purification processes, and are not easy to remove. SUMMARY

[0005] The present application aims to overcome the problems of high treatment cost and secondary pollution in the prior art, and provides a wastewater treatment device, an acid mine drainage wetland purification system and a treatment method for solving the purification effect of acid mine drainage, which has the advantages of low treatment cost, high cost performance, recyclable heavy metals, and deep purification of effluent.

[0006] To achieve the above-mentioned purpose, the present application provides a wastewater treatment device, comprising a wastewater treatment tank and a conveying device, characterized in that the wastewater treatment tank comprises a peripheral wall, an inner wall and a filler groove, the peripheral wall has a front water retaining wall and a rear water retaining wall arranged transversely, and two wall bodies arranged longitudinally between the front water retaining wall and the rear water retaining wall, the peripheral wall is longitudinally arranged with two inner walls inside, the peripheral wall is equal in height to the inner wall, a plurality of filler grooves arranged transversely are connected between the two inner walls, cavities are formed between adjacent filler grooves and between the filler grooves and the front water retaining wall and the rear water retaining wall of the peripheral wall for the flow of wastewater, each filler groove comprises a front intercepting wall body and a rear intercepting wall body arranged transversely, and a filler area separated by one or more connecting wall bodies arranged longitudinally between the wall bodies, and the filler area is filled with a wastewater treatment substrate; the conveying device is arranged below the filler area.

[0007] The top of the filler groove is obliquely cut to form a slope structure, so that the front intercepting wall body of each filler groove is higher than the rear intercepting wall body, and the front intercepting wall body of the next filler groove is lower than the rear intercepting wall body of the previous filler groove; the bottom of the front intercepting wall body is provided with an openable and closable inlet communicating the filler area and the cavity, and each filler area is provided with one openable and closable inlet.

[0008] The top of the peripheral wall and the inner wall is arranged as a stepped wall rim that steps downward along the direction of wastewater flow, wherein the stepped wall rim of the inner wall connected with the filler groove is not higher than the height of the front intercepting wall body of the filler groove, and the height of the stepped wall rim in contact with the cavity is not lower than the height of the rear intercepting wall body of the previous filler groove.

[0009] The inner wall on both sides of each cavity is provided with a gate, and the inner wall and the peripheral wall form a flow-through channel on both sides of the cavity and the filler groove, the flow-through channels on both sides are provided with barrier walls staggered therein, each flow-through channel is divided into a plurality of reflux channels by adjacent barrier walls, the inner wall in each reflux channel has only two gates, and each reflux channel is controllably connected with the front and rear cavities through the two gates.

[0010] The conveying device is arranged in the wastewater treatment tank and comprises a format valve connected with the filler area and a scraper, the upper end of the format valve is connected with the filler area, the lower end of the format valve is connected with the scraper, and the closing of the format valve controls the transmission of wastewater.

[0011] In order to achieve the above-mentioned purpose, the second aspect of the present application provides a wetland purification system for acid waste mine drainage, comprising limestone interception zone, biochar interception zone, confluence ditch, primary sedimentation tank, primary adsorption filter dam, neutralization dam, secondary sedimentation tank, secondary adsorption filter dam, anaerobic fermentation tank, primary subsurface flow wetland, secondary subsurface flow wetland and submerged plant tank which are sequentially connected, the limestone interception zone and the biochar interception zone are arranged at the lower part of the hillside runoff area, the confluence ditch collects wastewater overflowing from the biochar interception zone, the primary adsorption filter dam and the secondary adsorption filter dam and the neutralization dam are all arranged as the wastewater treatment device, the filler tank of the primary adsorption filter dam and the secondary adsorption filter dam is filled with biomass carbon, the filler tank of the neutralization dam is filled with limestone and calcite, the anaerobic fermentation tank is inoculated with anaerobic microorganisms and uses plant residues as fermentation material, plants are planted on the bank of the primary subsurface flow wetland and the secondary subsurface flow wetland, and the bottom of the pool is inoculated with sulfate-reducing bacteria with biomass carbon as the substrate, and aquatic plants are planted at the bottom of the submerged plant tank.

[0012] The limestone interception zone is arranged at the lower part of the hillside runoff area, extends into the ground by 0.15-0.3 meters, the upper part is 0.05-0.1 meters below the ground, the width is 0.2-0.4 meters, and the bottom of the pool is distributed with limestone, the hillside runoff and the shallow soil runoff in the mine area can all enter the limestone interception zone, and all the wastewater can be preliminarily neutralized.

[0013] The biochar interception zone is arranged at the lower part of the hillside runoff area, behind the limestone interception zone, extends into the ground by 0.15-0.3 meters, the upper part is 0.05-0.1 meters below the ground, and the width is 0.2-0.4 meters.

[0014] The confluence ditch is one or more ditches, which can collect the water flow in the project area to the primary sedimentation tank, and wetland plants are planted on the bank of the ditch;

[0015] The volume of the primary sedimentation tank meets the water collection of the project area, can regulate the water outflow speed, and can preliminarily settle the water pollutants, and wetland plants are planted on the bank of the primary sedimentation tank;

[0016] The wetland plants include one or more of Alternanthera philoxeroides, Alternanthera sessilis, vetiver, Miscanthus, Phragmites australis and reed, have strong water and soil conservation ability, strong heavy metal stress resistance, can grow in the mine area, grow on the bank, and can maintain water and soil.

[0017] The secondary sedimentation tank is provided with an inclined plate at the water inlet end, and the tank depth is preferably 3-5 meters;

[0018] The anaerobic fermentation tank is provided with fermentation material plant residues, which are selected from the plants planted on the bank of the confluence ditch and the bank of the primary sedimentation tank;

[0019] The substrate of the primary undercurrent pool bottom is biomass carbon, and one or more of Acorus calamus, Typha angustifolia, Sparganium stoloniferum is planted on the bank of the undercurrent pool, and sulfate-reducing bacteria is inoculated simultaneously; the substrate of the secondary undercurrent pool bottom is biomass carbon, and one or more of Phragmites communis, Eleocharis dulcis, Canna indica is planted on the bank of the undercurrent pool, and sulfate-reducing bacteria is inoculated simultaneously;

[0020] The submerged plant pool is planted with one or more of Potamogeton crispus, Hydrilla verticillata, Vallisneria denseserrulata, Chara braunii, Myriophyllum verticillatum, and the bottom plants grow fast, have large biomass and strong purification capacity; one or more of Alternanthera philoxeroides, Eichhornia crassipes, Miscanthus sinensis, Vetiveria zizanioides, Spartina anglica, Phragmites communis is planted on the bank of the submerged plant pool, and the bank plants have strong stress resistance, strong water and soil conservation capacity, can reduce water and soil loss of the bank slope and prevent pollution of the water body.

[0021] During wastewater treatment, the wastewater flows over the top end of the front water retaining wall of the wastewater treatment pool into the cavity, then enters the filler area through the openable and closable inlet at the lower end of the front intercepting wall of the filler tank, is treated, and then overflows from the rear intercepting wall to enter the next filler tank through the next cavity for treatment, and the wastewater treated by the wastewater treatment device flows out through the rear water retaining wall of the peripheral wall;

[0022] During wastewater treatment, the openable and closable inlet of at least one filler tank in the wastewater treatment pool is kept open as a standby filler tank, and the gates of the two cavities on the front and rear sides of the filler tank with the closed openable and closable inlet are opened to allow the wastewater to flow from the upper cavity to the lower cavity without passing through the filler tank with the closed openable and closable inlet;

[0023] When the filtration effect of the filler in any filler tank of the primary adsorption and filtration dam and the secondary adsorption and filtration dam on the wastewater decreases, or the pH increase value of the wastewater treated by the filler in any filler tank of the neutralization dam is less than the threshold value one or the reduction value of Cu 2+ ions is less than the threshold value one or the reduction value of SO4 2- ions is less than the threshold value one, the openable and closable inlet of the filler tank is closed, the gates of the two cavities on the front and rear sides of the filler tank in the same backflow channel are opened, then the filler tank conveying device works to discharge the filler and refill new filler, the openable and closable inlet of the standby filler tank is opened, and the gates of the two cavities on the front and rear sides of the standby filler tank in the same backflow channel are closed;

[0024] When the reduction value of SO4 2- ions of the wastewater treated by the filler in any filler tank of the neutralization dam is greater than the threshold value two, the pH of the wastewater discharged by the wastewater pool as a whole is greater than the threshold value three and the reduction value of Cu 2+When the ion content is less than the threshold value of 3, the packing tank is marked as an over-treated packing tank. At this time, the openable and closable inlets of at least one packing area in the over-treated packing tank are closed until the over-treated packing tank is no longer marked as an over-treated packing tank. If all the openable and closable inlets of the over-treated packing tank are closed, the gates that control the two cavities on the front and rear sides of the over-treated packing tank to be located in the same reflux channel are opened.

[0025] SO4 2- The threshold values ​​for ions 1 and 3 are dynamically set for the COD of the treated water discharged from the anaerobic digester.

[0026] The technical solution provided by the second aspect of the present invention solves the problem of COD in the treated water discharged from the anaerobic fermentation tank and SO4 in the wastewater discharged from the neutralization dam. 2- The present invention addresses the challenge of synchronizing the ratio of SO4 in wastewater to a suitable aquatic environment for sulfate-reducing bacteria growth. 2- The concentration of SO42- is adjusted according to the COD of the treated water discharged from the anaerobic digester, so that a portion of SO42- is reduced. 2- In the neutralization dam, calcium hydroxide forms a precipitate, and another portion forms SO42-. 2- In wetland purification, it is reduced to sulfur ions and forms precipitates with heavy metals.

[0027] A third aspect of the present invention provides a method for treating acidic mine wastewater, comprising the following steps:

[0028] Step (1) Source interception of surface and shallow soil: The limestone interception zone initially neutralizes the runoff from the slope and the runoff from the shallow soil, neutralizing the pH to 4-5; the subsequent wastewater enters the biochar interception zone, where iron hydroxide in the wastewater adsorbs other metal ions and some copper hydroxide co-precipitates.

[0029] Step (2) Collection and primary sedimentation: Water from the surface and shallow soil flows into the confluence ditch, and is then collected and stored in the primary sedimentation tank for preliminary sedimentation;

[0030] Step (3) Primary adsorption filtration: After the initial sedimentation in step (2), the acidic mine wastewater flows into the primary adsorption filtration dam and undergoes primary adsorption filtration with the biomass carbon filled in the dam to remove the suspended solids generated during the initial neutralization.

[0031] Step (4) Neutralization and sedimentation: After adsorption and filtration in step (3), the acidic mine wastewater flows into the neutralization dam. Inside the neutralization dam, the wastewater reacts with alkaline materials such as limestone and calcite. The pH value of the mine wastewater is adjusted to 5-6 within the neutralization dam, and the COD of the treated water discharged from the anaerobic fermentation tank is equal to the SO4 in the wastewater discharged from the neutralization dam. 2- The ratio is between 1.9 and 2.1, and then the wastewater goes to the secondary sedimentation tank for sedimentation reaction treatment;

[0032] Step (5) secondary adsorption filtration: after the neutralization and precipitation of the mine acid drainage in step (4), the mine acid drainage flows into the secondary adsorption filter dam, and the secondary adsorption filtration is carried out with the biomass carbon filled in the dam, so as to remove the suspended solids generated in the secondary neutralization;

[0033] Step (6) anaerobic fermentation: after the neutralization and precipitation of the mine acid drainage for multiple times, the mine acid drainage further flows into the anaerobic fermentation tank, and the anaerobic microorganisms in the anaerobic fermentation tank carry out fermentation with the plant residues as the carbon source, so as to decompose the plant residues into low-carbon small molecule COD, and the COD and SO4 2- The ratio of the two is between 1.9 and 2.1.

[0034] Step (7) wetland purification: after the neutralization, precipitation and adsorption filtration in the previous six steps, the wastewater further flows into the first and second subsurface flow tanks and the submerged plant tank, and the substrate adsorption is carried out with the biomass carbon in the two subsurface flow tanks, and the biological reaction is carried out with the sulfate-reducing bacteria, so as to reduce the sulfate ions in the wastewater to sulfur ions, and then the submerged plants adsorb the sulfur-containing pollutants in the wastewater and increase the dissolved oxygen in the water body, and the submerged plants can absorb the nitrogen, phosphorus and other nutrients in the water body.

[0035] Step (8) heavy metal recovery: the plants on the bank of the collection ditch in the harvesting system and the bank of the first precipitation tank are collected, and the biomass carbon is recovered after high-temperature pyrolysis, and then the heavy metals in the precipitates are recovered.

[0036] Further, the residence time of the wastewater in the first precipitation tank in step (2) is 12-48 hours, and the water quantity of the subsequent steps is controlled by adjusting the water quantity of the first precipitation tank; and the pH of the first precipitation tank is 4-5.

[0037] Further, the residence time of the wastewater in the second precipitation tank in step (4) is 12-48 hours.

[0038] Further, the sludge formed by the sludge of the precipitation reaction collected at the bottom of the second precipitation tank in step (4) is discharged, and the discharged sludge is dewatered and dried to form a mud cake which is naturally stacked.

[0039] Compared with the prior art, the beneficial effects of the present application are:

[0040] 1. By sequentially arranging the limestone interception belt and the biomass carbon interception belt before the runoff of the mountain, the surface flow and the shallow soil flow are neutralized, adsorbed and filtered, the pH value of the collected wastewater is improved, the iron ions in the wastewater are preliminarily precipitated, the pollutant concentration is reduced, which is beneficial to further treatment, reduces the difficulty of subsequent treatment, and overall reduces the operation and maintenance cost, and is beneficial to improve the water quality of the effluent. On the other hand, compared with the limestone and biomass carbon in the subsequent wetland, the limestone interception belt and the biomass carbon interception belt are more easily set, added and replaced.

[0041] 2. After the initial sedimentation and adsorption treatment, a secondary neutralization dam was installed to regulate the wastewater pH between 5 and 6. This precisely controls the concentration of copper ions, which are toxic to microorganisms in subsequent steps, causing them to precipitate in large quantities. This serves two purposes: firstly, it prevents microbial poisoning in the fermentation tank, allowing them to decompose plant residues and provide carbon and electron donors for sulfate-reducing bacteria in the subsequent subsurface flow tank; secondly, it avoids the need to select sulfate-reducing bacteria tolerant to metallic copper in the subsurface flow tank, reducing costs. Furthermore, it avoids the direct precipitation of iron and copper through a single neutralization and adsorption process, preventing the accumulation of heavy metal ions in the sediment at the bottom of the sedimentation tank, thus preventing secondary pollution and increased treatment costs. Simultaneously, a primary sedimentation tank and a primary adsorption filtration dam are installed upstream of the neutralization dam, reducing the particulate matter content and pollutant concentration in the water, minimizing clogging of the neutralization dam, and extending the service life of the packing material within the neutralization dam.

[0042] 3. Two adsorption filtration dams were set up. This allows heavy metals in the wastewater to be adsorbed by contact with a large amount of biochar. The heavy metals can be recovered by treating the biochar with adsorbed heavy metals, avoiding the need to recover heavy metals by treating neutralization precipitates.

[0043] 4. By setting up an anaerobic fermentation tank in advance, the wastewater is treated by anaerobic fermentation. The fermentation process produces a variety of small molecule carbons, which are beneficial to the survival of sulfate-reducing bacteria in the subsurface flow wetland and enhance the activity of sulfate-reducing bacteria in subsequent steps.

[0044] 5. The microorganisms and biomass carbon in the subsurface flow wetland adhere to each other, increasing the attachment area and allowing for full contact with wastewater, which is more conducive to the function of sulfate-reducing bacteria. At the same time, a large number of plants that adsorb COD are planted on the banks of the subsurface flow pool. When too much plant residue is added to the anaerobic fermentation tank, it can prevent the growth of sulfate-reducing bacteria in the subsurface flow pool from being inhibited, thus affecting the removal of sulfate ions from the wastewater.

[0045] 6. The end-of-pipe submerged plant pool further reduces nitrogen, phosphorus, COD, and heavy metals in the water, significantly improving the quality of the effluent.

[0046] 7. The adsorption filter dam and neutralization dam adopt wastewater treatment devices, which use multi-layer packing tanks for multiple reactions. Furthermore, the setting of gates and barrier walls makes it easier to replace the packing area without affecting wastewater treatment.

[0047] 8. Solved the problem of COD in the treated water discharged from the anaerobic fermentation tank and SO4 in the wastewater discharged from the neutralization dam. 2- The present invention addresses the challenge of synchronizing the ratio of SO4 in wastewater to a suitable aquatic environment for sulfate-reducing bacteria growth. 2- The concentration of SO42- is adjusted according to the COD of the treated water discharged from the anaerobic digester, so that a portion of SO42- is reduced. 2-In the neutralization dam, calcium hydroxide forms a precipitate, and another portion forms SO42-. 2- In wetland purification, sulfur ions are reduced to form precipitates with heavy metals. This allows the purification system to continuously maintain optimal wastewater treatment efficiency. Without the wastewater treatment device of this invention as a neutralization dam, the consumption of alkaline materials or the presence of SO4 in the wastewater... 2- Fluctuations in Cu in wastewater that is difficult to discharge stably from the neutralization dam 2+ SO4 2- The concentration and pH value of the pollutants cause the purification system to be ineffective in purifying wastewater.

[0048] Therefore, the purification system proposed in this invention has the advantages of low investment cost, simple operation, easy maintenance, low energy consumption, and good effluent quality, and is suitable for the ecological treatment of drainage from acidic abandoned mines. Attached Figure Description

[0049] Figure 1 This is a process flow diagram of the processing system of the present invention;

[0050] Figure 2 This is a schematic diagram of the wastewater treatment device of the present invention;

[0051] Figure 3 This is a schematic diagram of the wastewater treatment unit of the present invention. Detailed Implementation

[0052] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but the scope of protection is not limited to the description.

[0053] like Figure 1 As shown, an acidic mine drainage purification system includes a limestone interception zone, a biochar interception zone, a drainage ditch, a primary sedimentation tank, a primary adsorption filtration dam, a neutralization dam, a secondary sedimentation tank, a secondary adsorption filtration dam, an anaerobic fermentation tank, a primary subsurface flow tank, a secondary subsurface flow tank, and a submerged plant pond, all connected in sequence.

[0054] A limestone interception zone is deployed at the lower part of the hillside runoff area, extending 0.15-0.3 meters underground, with its upper part 0.05-0.1 meters below ground level and a width of 0.2-0.4 meters. Limestone is distributed at the bottom of the zone. This limestone interception zone collects and initially neutralizes surface runoff and shallow soil runoff from the mining area. A biochar interception zone is then installed after the limestone interception zone, extending 0.15-0.3 meters underground, with its upper part 0.05-0.1 meters below ground level and a width of 0.2-0.4 meters. The limestone and biochar interception zones neutralize, adsorb, and filter surface runoff and shallow soil runoff from the hillside, increasing the pH value of the collected wastewater and initially reducing pollutant concentration, which is beneficial for further treatment and reduces the difficulty of subsequent treatment.

[0055] The collecting ditch is one or more ditches, and water overflowed after being treated by the limestone interception zone and the biomass carbon interception zone flows into the collecting ditch, and then the water in the project area is collected to the primary sedimentation tank, and wet plants are planted on the banks of the ditch.

[0056] The volume of the primary sedimentation tank meets the water collection amount of the project area, so that the water outlet speed can be controlled, and the water pollutants can be preliminarily settled; and wet plants are planted on the banks of the primary sedimentation tank. The wet plants include one or more of Alternanthera philoxeroides, Alternanthera sessilis, Vetiveria zizanioides, Miscanthus sinensis, Phragmites australis and so on; the wet plants have strong water and soil conservation ability and strong heavy metal stress resistance, and can grow in the mining area and on the banks to maintain water and soil.

[0057] The primary adsorption filter dam, the secondary adsorption filter dam and the neutralization dam are all provided as wastewater treatment devices, such as the wastewater treatment device shown in Figure 2 The wastewater treatment device includes a wastewater treatment tank and a conveying device, and the wastewater treatment tank includes a peripheral wall 1, an inner wall 2 and a filler groove 3. The peripheral wall 1 has a front water retaining wall 4 and a rear water retaining wall 5 arranged transversely, and two wall bodies arranged longitudinally between the front water retaining wall 4 and the rear water retaining wall 5. Two inner walls 2 are arranged longitudinally in the peripheral wall 1, and the peripheral wall and the inner wall 2 are of the same height. A plurality of filler grooves 3 arranged transversely are connected between the two inner walls 2. Cavities 6 are formed between adjacent filler grooves 3 and between the filler grooves 3 and the front water retaining wall 4 and the rear water retaining wall 5 of the peripheral wall 1 for water flow. Each filler groove 3 includes a front intercepting wall body 7, a rear intercepting wall body 8 and one or more connecting wall bodies 9 arranged longitudinally between the wall bodies to divide the filler groove 3 into a plurality of filler areas 10. The filler areas 10 are filled with wastewater treatment substrates. The filler areas 10 are provided with a conveying device below.

[0058] The top of the filler groove 3 is obliquely cut to form a slope structure, so that the front intercepting wall body 7 of each filler groove 3 is higher than the rear intercepting wall body 8, and the front intercepting wall body 7 of the next filler groove 3 is lower than the rear intercepting wall body 8 of the previous filler groove 3. The bottom of the front intercepting wall body 7 is provided with an openable and closable inlet 11 connected with the filler area 10 and the cavity 6. Each filler area 10 is provided with one openable and closable inlet 11.

[0059] The top of the peripheral wall 1 and the inner wall 2 is provided with a stepped wall rim that is stepped downward along the direction of water flow. The stepped wall rim connected with the filler groove 3 of the inner wall 2 is not higher than the height of the front intercepting wall body 7 of the filler groove 3, and the height of the stepped wall rim in contact with the cavity 6 is not lower than the height of the rear intercepting wall body 8 of the previous filler groove 3.

[0060] The inner wall 2 on both sides of each cavity 6 is provided with a gate at the upper end, and the inner wall 2 and the outer wall 1 form a flow channel 12 on both sides of the cavity and the filler groove, and the flow channels 12 on both sides are provided with barrier walls 13 staggered therein, and each flow channel 12 is divided into a plurality of reflux channels by the adjacent barrier walls 13, and the inner wall 2 in each reflux channel has only two gates, and each reflux channel is controllably connected with the two cavities in front and back through the two gates.

[0061] The conveying device comprises a format valve 15 connected with the filler area 10 and a scraper 16, and the upper end of the format valve 15 is connected with the filler area 10, and the lower end is connected with the scraper 16.

[0062] The filler grooves of the primary adsorption filter dam and the secondary adsorption filter dam are filled with biomass carbon, and the filler grooves of the neutralization dam are filled with blocky alkaline fillers such as limestone and calcite.

[0063] The front and rear water retaining walls 4 and 5 between the two inner walls 2 can be designed to be lower than the height of the inner wall.

[0064] During wastewater treatment, wastewater enters the cavity 6 from the upper end of the front water retaining wall 4 of the wastewater treatment tank, and at this time all the gates 14 are closed, and after the wastewater enters the cavity 6, it enters the filler area 10 through the openable and closable inlet at the lower end of the front intercepting wall 7 of the filler groove 3, and after being treated by the wastewater treatment substrate, it overflows from the rear intercepting wall 8 to the next cavity 6, and then the process described above is repeated, and finally after being treated by the last filler groove 3, it overflows from the rear water retaining wall of the outer wall to the next stage of the wastewater treatment tank, and the process is closed with the gate closed.

[0065] If the substrate of the filler groove 3 needs to be replaced, the two gates 14 adjacent to the front and rear of the filler groove are controlled to be opened, and the openable and closable inlet 11 at the lower end of the front intercepting wall 7 of the filler groove is closed.

[0066] Specifically, during wastewater treatment, at least one filler groove in the wastewater treatment tank is kept open as a standby filler groove, and the gates of the two cavities on the front and rear sides of the filler groove with the closed openable and closable inlet are opened, so that the wastewater flows from the upper stage cavity to the lower stage cavity without passing through the filler groove with the closed openable and closable inlet.

[0067] When the filtering effect of the filler in any filler groove of the primary adsorption filter dam and the secondary adsorption filter dam on the wastewater decreases, or the pH of the wastewater treated by the filler in any filler groove of the neutralization dam increases by less than a threshold value one or the decrease of Cu 2+ ions is less than a threshold value one or the decrease of SO4 2-When the ion reduction value is less than threshold one, the openable inlet of the packing tank is closed, and the gates controlling the two cavities on the front and rear sides of the packing tank located in the same return channel are opened. Then, the packing tank conveying device operates, discharging the packing and filling it with new packing. At the same time, the openable inlet of the spare packing tank is opened, and the gates controlling the two cavities on the front and rear sides of the spare packing tank located in the same return channel are closed. Threshold one is the Cu content of the wastewater discharged from the packing tank in the neutralization dam. 2+ Ions, SO4 2- The concentration should be reduced from the design value, or the pH should be increased from the design value.

[0068] SO42 content of wastewater treated by the filler in any filler tank of the dam 2- The ion reduction value is greater than threshold two, and the pH of the wastewater discharged from the wastewater tank as a whole is greater than threshold three, and Cu 2+ When the ion concentration is less than the threshold value of 3, the packing tank is marked as an over-treated packing tank. This may be due to a reduction in wastewater volume or dilution of wastewater caused by heavy rain. At this time, the openable and closable inlets of at least one packing area in the over-treated packing tank are closed until the over-treated packing tank is no longer marked as an over-treated packing tank. If all openable and closable inlets of the over-treated packing tank are closed, the gates in the two cavities on the front and rear sides of the over-treated packing tank that are located in the same return channel are opened.

[0069] Threshold 2 is the SO4 content of the wastewater discharged from the filling tank in the neutralization dam. 2- The concentration is reduced from the design value.

[0070] SO4 2- The threshold values ​​for ions one and three are dynamically set along with the COD of the treated water discharged from the anaerobic digester. The technical solution provided by the second aspect of this invention solves the problem of COD in the treated water discharged from the anaerobic digester being lower than that in the SO42-containing wastewater discharged from the neutralization dam. 2- The present invention addresses the challenge of synchronizing the ratio of SO4 in wastewater to a suitable aquatic environment for sulfate-reducing bacteria growth. 2- The concentration of SO42- is adjusted according to the COD of the treated water discharged from the anaerobic digester, so that a portion of SO42- is reduced. 2- In the neutralization dam, calcium hydroxide forms a precipitate, and another portion forms SO42-. 2- In wetland purification, it is reduced to sulfur ions and forms precipitates with heavy metals.

[0071] For example: When replacing the packing in the first packing tank 3, open the front and rear cavities of the first packing tank 3 in the same return channel (with the water flow direction as the front). Figure 2Gate 141 and gate 2142 are located in the return channel on the right side of the second and third cavities. Wastewater enters the second cavity 6 of the first packing tank 3 from the first cavity 6 through gate 141 and gate 2142, and then enters from the openable inlet 11 at the lower end of the second packing tank 3, and reacts with the packing in sequence.

[0072] If the packing in the second packing trough 3 is replaced, then the second and third cavities are opened in the same return channel. Figure 2 Gates 142 and 143 (located in the return channels on the left side of the second and third cavities) are used to treat wastewater in the first packing tank 3. After treatment, the wastewater enters the second cavity 6 between the first and second packing tanks 3. Since the openable inlet 11 at the lower end of the second packing tank 3 is closed, the wastewater does not enter the second packing tank. Due to the presence of the barrier wall, the wastewater enters the third cavity 6 between the second and third packing tanks 3 through gates 142 and 143. Then, it enters the packing zone 10 from the openable inlet 11 at the lower end of the third packing tank 3 and reacts with the packing material in sequence.

[0073] If the packing in the third packing trough 3 is replaced, then the third and fourth cavities will be opened in the same return channel. Figure 2 Gates 143 and 144 (located in the return channel on the right side of the third and fourth cavities) are used to treat the wastewater. After passing through the first two packing tanks 3, the wastewater enters the third cavity 6 between the second and third packing tanks 3. Since the openable inlet 11 at the lower end of the third packing tank 3 is closed, the wastewater does not enter the third packing tank 3. Instead, it enters the fourth cavity 6 between the third and fourth packing tanks 3 through gates 143 and 144 in the return channel. Then, it enters the packing zone 10 from the openable inlet at the lower end of the fourth packing tank 3 and reacts with the packing material in sequence.

[0074] The inlet of the secondary sedimentation tank is equipped with inclined plates, and the tank depth is 3-5 meters. The structure of the secondary adsorption filter dam is the same as that of the primary adsorption filter dam. After purification in the preceding stages, the water quality is improved to a certain extent.

[0075] Anaerobic fermentation tanks use plant residues as fermentation material. Under the metabolic activities of anaerobic bacteria such as yeast and lactic acid bacteria, the plant residues are degraded and decomposed into low-carbon small molecules, providing carbon sources, trace elements and electron donors for the growth of sulfate-reducing bacteria in subsequent processes, thereby improving the activity of sulfate-reducing bacteria.

[0076] The substrate at the bottom of the primary subsurface flow tank is biomass carbon, and one or more of the following plants—such as calamus, cattail, and black sedge—are planted along the banks, along with sulfate-reducing bacteria. The secondary subsurface flow tank is set up in the same way as the primary subsurface flow tank.

[0077] The submerged plant pool is planted with one or more of Potamogeton crispus, Hydrilla verticillata, Vallisneria, Nitella, Fox tail rush, and the shore of the submerged plant pool is planted with one or more of Eupatorium adenophorum, Lotus, Miscanthus, Vetiver, South Di, and reed, and the plants on the shore of the submerged plant pool have strong stress resistance and strong water and soil conservation capacity, reducing water and soil loss on the slope and preventing pollution of the water body.

[0078] The plant residues in the anaerobic fermentation pool come from the plants planted on the shore of the confluence ditch, the first-stage sedimentation pool, the first-stage subsurface pool, and the second-stage subsurface pool.

[0079] The water quality monitoring of the acid mine drainage treated in the above purification process is shown in Tables 1 and 2.

[0080] Table 1

[0081]

[0082]

[0083] Table 2

[0084]

[0085] Based on the above purification system, an acid mine drainage treatment method comprises the following steps:

[0086] Step (1) source interception of the ground surface and shallow soil: the limestone interception belt preliminarily neutralizes the runoff on the slope surface and the shallow soil runoff, and the pH is neutralized to 4-5; the wastewater after pH neutralization enters the biomass charcoal interception belt, and the iron and part of the copper hydroxide in the slope runoff and the shallow soil runoff are intercepted through adsorption, and various metal ions are co-precipitated with the iron hydroxide through adsorption.

[0087] Step (2) collection and first-stage sedimentation: the water flow in the ground surface and shallow soil enters the confluence ditch, and then is collected and stored in the first-stage sedimentation pool, and the water flow stays in the first-stage sedimentation pool for 12-48 hours for preliminary sedimentation, and the water flow amount through the first-stage sedimentation pool can be adjusted to adjust the water flow amount in the subsequent steps; the primary sediment is mainly the silt brought by the runoff and the chemical sediment caused by the preliminary neutralization (pH 4-5).

[0088] Step (3) first-stage adsorption filtration: after the mine acid drainage is preliminarily sedimented in step (2), it flows into the first-stage adsorption filtration dam through the water retaining wall, and is subjected to first-stage adsorption filtration with the biomass carbon filled in the dam; the first-stage filtration is used to remove the suspended matter generated by the preliminary neutralization.

[0089] Step (4) neutralization and precipitation: after the mine acid drainage is filtered by adsorption in step (3), it flows into a neutralization dam, where it is in contact with alkaline materials such as limestone and calcite to react, and then reaches a secondary sedimentation tank, where it stays for 12-48 hours. In the neutralization dam, the pH value of the mine wastewater is adjusted to 5-6, and the ratio of the COD of the treated water discharged from the anaerobic fermentation tank to the SO4 2- in the wastewater discharged from the neutralization dam is between 1.9 and 2.1. At the same time, the dissolution and hydrolysis of the carbonate in the limestone provide a large amount of hydroxyl ions, which further precipitate the copper ions in the wastewater. In the secondary sedimentation tank, the secondary precipitate is the copper hydroxide precipitate formed in the neutralization dam, and at this time a part of the sulfate ions will form calcium sulfate with very small solubility, which will all be collected at the bottom of the secondary sedimentation tank to form sludge to be discharged, which will be dewatered and dried in a drying plant, and the dried mud cake will be naturally stored.

[0090] Step (5) secondary adsorption filtration: after the mine acid drainage is neutralized and precipitated in step (4), it flows over a water retaining wall into a secondary adsorption filtration dam, where it is subjected to secondary adsorption filtration with the biomass carbon filled in the dam; the secondary filtration is used to remove the suspended solids generated by the secondary neutralization.

[0091] Step (6) anaerobic fermentation: after the mine acid wastewater is neutralized and precipitated for multiple times, the water quality is improved, and then it further flows into an anaerobic fermentation tank, while plant residues are also fed into the tank for fermentation, which provides carbon source for anaerobic microorganisms and reduces the oxidation-reduction potential of the water body; at the same time, the plant residues are decomposed into low-carbon small molecules to provide substrates for subsequent sulfate-reducing bacteria.

[0092] Step (7) wetland purification: after the neutralization, precipitation, adsorption filtration in the previous 6 steps, the wastewater further flows into a primary subsurface flow tank, a secondary subsurface flow tank and a submerged plant tank, and after being subjected to substrate adsorption with the biomass carbon in the two subsurface flow tanks, the ratio of the COD of the treated water discharged from the anaerobic fermentation tank to the SO4 2- in the wastewater discharged from the neutralization dam is reduced to 1.4-1.8, and the sulfate ions are reduced to sulfur ions by biological reaction with the sulfate-reducing bacteria, and then the wastewater is in contact with the submerged plants again, the submerged plants adsorb the sulfur-containing pollutants, increase the dissolved oxygen in the water body, slow down the water flow, which is conducive to controlling the resuspension of the bottom mud containing sulfur precipitate and fixing the bottom mud, and the submerged plants can also absorb the nitrogen, phosphorus and other nutrients in the water body.

[0093] Step (8) heavy metal recovery: the plants on the banks of the collection ditch in the harvesting system and the banks of the primary sedimentation tank are subjected to high-temperature pyrolysis to recover biochar, and then the precipitate is collected to recover the heavy metals therein.

[0094] Since the concentration of metal ions and the pH of the solution, the solubility product of hydroxide exist the following relationship:

[0095] lg[M n+ ] = lgKsp + 14n-npH

[0096] where [M n+ ] is the concentration of metal ions, Ksp is the solubility product constant of the metal hydroxide; n is the valence of the metal ion.

[0097] According to the above formula, the pH at which each metal ion completely forms a precipitate of hydroxide can be calculated according to Table 1. According to Formula 1, in the acid mine drainage treatment method of the present application, most of the heavy metal ions do not directly form a precipitate and transfer to the sludge during the two neutralization treatments of Step (1) and Step (4), thus avoiding secondary pollution of the environment, and instead, most of the heavy metal ions are enriched in Steps (6) to (8) of the subsequent process.

[0098] Meanwhile, the pH of the acid mine wastewater after neutralization in Step (4) is 5 to 6, which is suitable for anaerobic microbial fermentation of plant residues and reduces the oxidation-reduction potential of the water. As shown in Table 2, Step (4) removes most of the copper ions, avoiding the inhibition of the activity of lactate dehydrogenase by copper ions, reducing the generation of lactic acid, and also avoiding the possible inhibition of the growth of lactic acid bacteria and yeast by copper ions, leading to a decrease in the fermentation rate. Step (4) also removes part of the SO4 2- ions, and by controlling the amount of filler tank in the neutralization dam participating in wastewater treatment, the concentration of SO4 2- in the wastewater discharged from the neutralization dam can be adjusted according to the COD of the treated water discharged from the anaerobic fermentation tank, so that the ratio of the COD of the treated water discharged from the anaerobic fermentation tank to the SO4 2- in the wastewater discharged from the neutralization dam is between 1.9 and 2.1. The COD in the treated water discharged from the anaerobic fermentation tank is adsorbed by plants in the first subsurface flow tank, and the ratio of the COD in the water to the SO4 2- in the wastewater discharged from the neutralization dam is reduced to 1.4 to 1.8, which is conducive to the propagation of sulfate-reducing bacteria in the wetland and increases the amount of SO4 2- reduced to sulfur ions in the wetland purification and precipitated with heavy metals.

[0099] In Step (6), the plant residues are anaerobically fermented by lactic acid bacteria and yeast, providing a large amount of low-carbon small molecules (such as lactic acid and acetic acid) for sulfate-reducing bacteria to decompose and utilize as substrates. Since most of the copper ions are removed in Step (4), the toxicity of copper ions to sulfate-reducing bacteria is also avoided, so there is no need to specially screen sulfate-reducing bacteria that are resistant to copper ions. In Step (6), since the subsurface flow tank is planted with Acorus calamus, Typha angustifolia, and Sparganium stoloniferum, which have strong adsorption capacity for COD, when too much plant residue is added, the plants in the subsurface flow tank can further adsorb the excess small molecule COD, stabilizing the COD / SO4 2-The concentration ratio gives sulfate-reducing bacteria a competitive advantage over other bacteria, which is beneficial for improving the reduction of SO4 by sulfate-reducing bacteria. 2- The ability to control the amount of plant residue added in this step is such that the mass ratio of COD small molecules after decomposition of plant residue in the anaerobic fermentation tank to sulfate ions in the wastewater exceeds 1.8. In this way, when the wastewater enters the subsurface flow tank, after some of the COD small molecules are adsorbed, this ratio can be reduced to 1.4-1.8.

[0100] The water quality monitoring results of the acidic mine wastewater treated according to the above purification process are shown in Table 3 below. After seven treatment steps, the water quality was significantly improved.

[0101] Table 3

[0102]

[0103] Example 2

[0104] This embodiment provides a wetland purification system for acidic mine drainage, comprising a limestone interception zone, a biochar interception zone, a drainage ditch, a primary sedimentation tank, a primary adsorption filtration dam, a secondary sedimentation tank, a secondary adsorption filtration dam, an anaerobic fermentation tank, a primary subsurface flow tank, a secondary subsurface flow tank, and a submerged plant pond, all connected in sequence. Compared to Embodiment 1, this embodiment lacks a neutralization dam treatment step (i.e., the limestone in the neutralization dam is not refilled after complete consumption). Specific treatment steps are as described in Embodiment 1.

[0105] The water quality monitoring results for the acidic mine wastewater treated according to the above purification process are shown in Table 4 below.

[0106] Table 4

[0107]

[0108] As shown in the table above, when the wastewater is not neutralized again using alkaline materials such as limestone and calcite before entering the secondary sedimentation tank, the pH value at the outlet of the secondary sedimentation tank is in the range of 4-5. At this time, in addition to iron ions, the content of other metal ions such as copper ions in the wastewater remains at a high concentration and has not completely settled into the sludge as in Example 1. When the wastewater directly enters the anaerobic fermentation tank, most of the heavy metal ions in the wastewater are toxic to the anaerobic microorganisms (such as yeast and lactic acid bacteria) in the anaerobic fermentation tank, especially copper ions, cadmium ions and lead ions in the wastewater. Therefore, the activity of anaerobic microorganisms in the anaerobic fermentation tank is severely affected, and the COD content in the wastewater after fermentation is low, which leads to the slow reproduction of sulfate-reducing bacteria in the subsurface flow tank and the inability to effectively reduce sulfate.

[0109] On the one hand, due to the inactivation of anaerobic microorganisms in the anaerobic fermentation tank, the plant residues are not decomposed into small molecule COD to serve as the carbon source substrate for the sulfate-reducing bacteria in the subsurface flow tank, and in the absence of the carbon source substrate, the sulfate-reducing bacteria cannot reduce a large amount of sulfate ions in the wastewater to hydrogen sulfide. On the other hand, the mine wastewater entering the subsurface flow tank also contains a large amount of metal ions, which also affects the activity of ordinary sulfate-reducing bacteria. Although the activity of the sulfate-reducing bacteria is not high, the plants in the subsurface flow tank and the resting tank can further adsorb the COD and metal ions in the wastewater, so that the concentrations thereof are slightly reduced, but the concentrations of the heavy metal ions and the sulfate ions in the final effluent are still high, which still causes great pollution to the environment.

[0110] In the above examples, the plants such as Acorus calamus, Typha angustifolia and Sparganium stoloniferum are planted on the bank of the subsurface flow tank, so as to absorb the COD of the wastewater at the outlet of the anaerobic fermentation tank, and control the ratio of the COD to SO42- in the wastewater to be within 1.4-1.8. After the wastewater enters the primary subsurface flow tank, the ratio of the COD to SO42- in the wastewater is reduced to 1.4-1.8, which is beneficial to the sulfate-reducing bacteria to be in a competitive advantage position relative to other bacteria, and is beneficial to the large-scale reproduction of the sulfate-reducing bacteria. If the plants such as Acorus calamus, Typha angustifolia and Sparganium stoloniferum are not planted on the bank of the subsurface flow tank, the plant residues are decomposed into a large amount of small molecule COD under the action of the microorganisms in the anaerobic fermentation tank, and the ratio of the COD to the sulfate ions in the wastewater exceeds 2.2. When such wastewater enters the subsurface flow tank, the excess COD in the wastewater cannot be adsorbed and removed due to the absence of the plants such as Acorus calamus, Typha angustifolia and Sparganium stoloniferum in the subsurface flow tank, which leads to the inhibition of the growth of the inoculated sulfate-reducing bacteria in the subsurface flow tank, and the sulfate-reducing bacteria cannot reduce the sulfate ions in the water to sulfur ions in time, so the sulfate-reducing bacteria cannot form sulfide precipitates with other heavy metal ions, which is not conducive to the removal of the heavy metals. 2- 2- In the above examples, the plants such as Acorus calamus, Typha angustifolia and Sparganium stoloniferum are planted on the bank of the subsurface flow tank, so as to absorb the COD of the wastewater at the outlet of the anaerobic fermentation tank, and control the ratio of the COD to SO42- in the wastewater to be within 1.4-1.8. After the wastewater enters the primary subsurface flow tank, the ratio of the COD to SO42- in the wastewater is reduced to 1.4-1.8, which is beneficial to the sulfate-reducing bacteria to be in a competitive advantage position relative to other bacteria, and is beneficial to the large-scale reproduction of the sulfate-reducing bacteria. If the plants such as Acorus calamus, Typha angustifolia and Sparganium stoloniferum are not planted on the bank of the subsurface flow tank, the plant residues are decomposed into a large amount of small molecule COD under the action of the microorganisms in the anaerobic fermentation tank, and the ratio of the COD to the sulfate ions in the wastewater exceeds 2.2. When such wastewater enters the subsurface flow tank, the excess COD in the wastewater cannot be adsorbed and removed due to the absence of the plants such as Acorus calamus, Typha angustifolia and Sparganium stoloniferum in the subsurface flow tank, which leads to the inhibition of the growth of the inoculated sulfate-reducing bacteria in the subsurface flow tank, and the sulfate-reducing bacteria cannot reduce the sulfate ions in the water to sulfur ions in time, so the sulfate-reducing bacteria cannot form sulfide precipitates with other heavy metal ions, which is not conducive to the removal of the heavy metals.​

Claims

1. A wastewater treatment device, comprising a wastewater treatment tank and a conveying device, characterized in that, The wastewater treatment tank includes an outer wall, an inner wall, and a packing trough. The outer wall has a horizontally arranged front and rear water-retaining wall, and two longitudinally arranged walls located between the front and rear water-retaining walls. Inside the outer wall, there are two longitudinally arranged inner walls. The outer wall and the inner walls are at the same height. Several horizontally arranged packing troughs are connected between the two inner walls. Cavities are formed between adjacent packing troughs and between the packing troughs and the front and rear water-retaining walls of the outer wall to allow wastewater to flow. Each packing trough includes a horizontally arranged front and rear intercepting wall, and a packing area divided by one or more longitudinally arranged connecting walls. The packing area is filled with wastewater treatment matrix. A conveying device is provided below the packing area. The top of the packing trough is cut at an angle to form a sloping structure, so that the front intercepting wall of each packing trough is higher than the rear intercepting wall, and the front intercepting wall of the next packing trough is lower than the rear intercepting wall of the previous packing trough; the bottom of the front intercepting wall is provided with an openable and closable inlet connecting the packing area and the cavity, and each packing area is provided with one openable and closable inlet. The top of both the outer and inner walls is set as a stepped wall edge that descends in the direction of wastewater flow. The stepped wall edge connecting the inner wall to the packing trough is not higher than the height of the front intercepting wall of the packing trough, and the height of the stepped wall edge at the contact point with the cavity is not lower than the height of the rear intercepting wall of the previous packing trough. Each cavity is provided with gates on the inner walls on both sides. A flow channel is formed between the inner wall and the outer wall on both sides of the cavity and the filling tank. The flow channels on both sides are staggered with barrier walls. Each flow channel is divided into multiple return channels by adjacent barrier walls. The inner wall of each return channel has only two gates. Each return channel is controllably connected to the front and rear cavities through the two gates. The conveying device includes a grid valve and a scraper conveyor connected to the packing area. The upper end of the grid valve is connected to the packing area, and the lower end is connected to the scraper conveyor. The opening and closing of the grid valve controls the replacement of the packing.

2. An acidic mine drainage purification system, characterized in that, The system comprises, in sequence, a limestone interception zone, a biochar interception zone, a confluence channel, a primary sedimentation tank, a primary adsorption filtration dam, a neutralization dam, a secondary sedimentation tank, a secondary adsorption filtration dam, an anaerobic fermentation tank, a primary subsurface flow tank, a secondary subsurface flow tank, and a submerged plant tank. The limestone and biochar interception zones are set along the foot of the slope at the lower part of the runoff generation area. The confluence channel collects wastewater overflowing from the biochar interception zone. The primary, secondary, and neutralization dams are all configured as the wastewater treatment device described in claim 1. The packing troughs of the primary and secondary adsorption filtration dams are filled with biochar. The packing troughs of the neutralization dam are filled with limestone and calcite. The anaerobic fermentation tank is inoculated with anaerobic microorganisms and uses plant residues as fermentation material. The banks of the primary and secondary subsurface flow tanks are planted with plants, and the bottom of the tanks is inoculated with sulfate-reducing bacteria using biochar as a substrate. The bottom of the submerged plant tank is planted with aquatic plants.

3. The acidic mine drainage purification system according to claim 2, characterized in that, The limestone interception zone extends 0.15-0.3 meters underground, with its upper part 0.05-0.1 meters below the ground surface and a width of 0.2-0.4 meters. Limestone is distributed at the bottom of the pool. The limestone interception zone collects and preliminarily neutralizes the surface runoff and shallow soil runoff from the mining area. The biochar interception zone is set after the limestone interception zone, extending 0.15-0.3 meters underground, with its upper part 0.05-0.1 meters below the ground surface and a width of 0.2-0.4 meters.

4. The acidic mine drainage purification system according to claim 2, characterized in that, During wastewater treatment, the wastewater overflows from the top of the front retaining wall of the wastewater treatment tank and enters the cavity. Then, it enters the packing area from the lower end of the front intercepting wall of the packing tank for treatment. It then overflows from the rear intercepting wall and enters the next packing tank from the next cavity for treatment. The wastewater treated by the wastewater treatment device overflows from the rear retaining wall of the outer perimeter wall and flows out. During wastewater treatment, at least one of the openable and closable inlets of the wastewater treatment tank is kept closed as a backup packing tank, and the gates of the two cavities on the front and rear sides of the packing tank with the closed openable and closable inlet located in the same return channel are opened, so that the wastewater flows from the upper cavity to the lower cavity without passing through the packing tank with the closed openable and closable inlet. When the filtration efficiency of the packing material in either the primary or secondary adsorption filtration dam decreases, or when the pH increase of the treated wastewater in either packing tank of the neutralization dam falls below the pH threshold or Cu 2+ The decrease value is less than Cu 2+ Threshold one or SO4 2- The reduction value is less than that of SO4 2- When the threshold is reached, the openable inlet of the packing trough is closed and the gates that control the two cavities on the front and rear sides of the packing trough located in the same return channel are opened. Then the packing trough conveying device works to discharge the packing and fill it with new packing. At the same time, the openable inlet of the spare packing trough is opened and the gates that control the two cavities on the front and rear sides of the spare packing trough located in the same return channel are closed. SO42 content of wastewater treated by the filler in any filler tank of the dam 2- The decrease value is greater than threshold two, the pH of the wastewater discharged from the wastewater tank as a whole is greater than threshold three, and Cu 2+ When the value is less than the threshold of four, the packing trough is marked as an over-processed packing trough. At this time, the openable and closable inlets of at least one packing area in the over-processed packing trough are closed until the over-processed packing trough is no longer marked as an over-processed packing trough. If all the openable and closable inlets of the over-processed packing trough are closed, the gates in the same return channel of the two cavities on the front and rear sides of the over-processed packing trough are opened. SO4 2- Threshold 1 and threshold 2 are dynamically set according to the COD of the treated water discharged from the anaerobic digester.

5. The acidic mine drainage purification system according to claim 2, characterized in that, The banks of the confluence channels and primary sedimentation ponds are planted with wetland plants, including one or more of the following: Alternanthera philoxeroides, Alternanthera philoxeroides, Vetiver, Miscanthus sinensis, Dioscorea opposita, and Reed. The bottom of the submerged plant ponds is planted with one or more of the following: Potamogeton crispus, Hydrilla verticillata, Vallisneria natans, Elodea nuttallii, and Myriophyllum spicatum. The banks of the primary and secondary subsurface flow ponds are planted with one or more of the following: Acorus calamus, Typha orientalis, and Sparganium stoloniferum.

6. A method for treating acidic mine wastewater, comprising purifying acidic mine wastewater based on the acidic mine wastewater purification system of any one of claims 2-5, characterized in that, Includes the following steps, Step (1) Source interception of surface and shallow soil: Limestone interception zone initially neutralizes slope runoff and shallow soil runoff, neutralizing pH to 4-5; The wastewater then enters the biochar interception zone, where iron hydroxide in the wastewater adsorbs other metal ions and some copper hydroxide co-precipitates. Step (2) Collection and primary sedimentation: Water from the surface and shallow soil flows into the confluence ditch, and is then collected and stored in the primary sedimentation tank for preliminary sedimentation; Step (3) Primary adsorption filtration: After the initial sedimentation in step (2), the acidic mine wastewater flows into the primary adsorption filtration dam and undergoes primary adsorption filtration with the biomass carbon filled in the dam to remove the suspended solids generated during the initial neutralization. Step (4) Neutralization and sedimentation: After adsorption and filtration in step (3), the acidic mine wastewater flows into the neutralization dam. Inside the neutralization dam, the wastewater reacts with limestone and calcite. The pH value of the mine wastewater inside the neutralization dam is controlled to be adjusted to 5-6, and the COD of the treated water discharged from the anaerobic fermentation tank is equal to the SO4 in the wastewater discharged from the neutralization dam. 2- The ratio is between 1.9 and 2.1, and then the wastewater goes to the secondary sedimentation tank for sedimentation reaction treatment; Step (5) Secondary adsorption filtration: After neutralization and sedimentation in step (4), the acidic mine wastewater flows into the secondary adsorption filtration dam and undergoes secondary adsorption filtration with the biomass carbon filled in the dam to remove suspended solids generated during the secondary neutralization. Step (6) Anaerobic fermentation: After multiple neutralizations and sedimentations, the acidic wastewater from the mine flows into the anaerobic fermentation tank. The anaerobic microorganisms in the anaerobic fermentation tank use plant residues as a carbon source to ferment the plant residues into low-carbon small molecules COD. Step (7) Wetland purification: After the neutralization, sedimentation, adsorption and filtration of the previous 6 steps, the wastewater enters the first-level submersible flow tank, the second-level submersible flow tank and the submerged plant tank in turn. It undergoes matrix adsorption with the biomass carbon in the two submersible flow tanks and biological reaction with sulfate-reducing bacteria to reduce sulfate ions in the wastewater to sulfur ions. Subsequently, the submerged plants adsorb sulfur-containing pollutants in the wastewater and increase the dissolved oxygen in the water. At the same time, the submerged plants can absorb nitrogen and phosphorus in the water. Step (8) Heavy metal recovery: Harvest the plants on the banks of the confluence ditches and the primary sedimentation tank within the system, perform high-temperature pyrolysis to recover biochar, and then collect the sediment to recover the heavy metals.

7. The processing method according to claim 6, characterized in that, In step (2), the wastewater stays in the primary sedimentation tank for 12-48 hours. The outflow from the primary sedimentation tank is adjusted to control the amount of water treated in subsequent steps. The pH of the primary sedimentation tank is 4-5.

8. The processing method according to claim 6, characterized in that, In step (4), the wastewater stays in the secondary sedimentation tank for 12-48 hours.

9. The processing method according to claim 6, characterized in that, In step (4), the sediment from the sedimentation reaction that accumulates at the bottom of the secondary sedimentation tank forms sludge and is then discharged. The discharged sludge is dewatered and dried to form mud cakes that are naturally stored.

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