Mine wastewater treatment system and method for producing alkali through coupling reduction of red mud organic matters

Abstract

The invention provides a mine wastewater treatment system and method for producing alkali through coupling reduction of red mud organic matters, and belongs to the technical field of ecological restoration. The treatment system comprises a pre-sedimentation tank, a reaction tank and a post-sedimentation tank which are connected in sequence; the reaction tank is filled with filler, and the filler comprises inorganic filler and composite filler which are filled from bottom to top in a layered manner; the composite filler is formed by mixing biomass and red mud according to a certain ratio, fermenting and decomposing, and specifically, the biomass and the red mud are uniformly mixed according to a preset weight ratio; performing natural fermentation for preset first time; turning is carried out once every preset second time in the composting period, the overall water content and temperature are controlled within preset intervals, and composting is completed after preset total turning times. The treatment method comprises the steps of preparation of the composite filler, construction of a treatment system, hydraulic retention of to-be-treated wastewater in the treatment system, and regeneration of the waste composite filler to prepare the repair soil. The treatment effect on acid mine wastewater and the remediation effect on mine soil are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of ecological restoration, and specifically relates to a mine wastewater treatment system and method for red mud organic matter coupled reduction to produce alkali. Background Art

[0002] After closure, coal mines are prone to produce acidic mine wastewater with strong acidity and high iron and manganese content, which causes serious harm to the ecological environment and urgently needs to be polluted.

[0003] Red mud (RM: Red Mud) Red mud is a high-salinity alkaline solid waste produced in the process of aluminum refining from bauxite. Because it contains a large amount of Fe2O3 and is red, it is usually called red mud. The main components of red mud are generally SiO2, Al2O3, CaO, Fe2O3 and Na2O. Red mud is alkaline and adsorbent. However, red mud has a poor physical structure, lacks nutrients, and is difficult to soil after dealkalization. It is usually not directly used for growing plants.

[0004] The reduction alkali production system is a passive treatment technology for acid mine wastewater. It has good stability in treating mine wastewater with low acidity load and low daily operation and maintenance management costs. The reduction alkali production system mainly consists of three layers: water layer, composite filler layer, and alkali production medium layer. The water layer mainly isolates oxygen and precipitates some metal ions; the composite filler layer mainly provides a living environment for microorganisms, reduces sulfate and trivalent iron, and can also remove some metal ions through adsorption and neutralization precipitation. The limestone layer mainly plays a role in raising the pH of the water body, and the unreduced trivalent iron ions and aluminum ions will be precipitated and removed in the limestone layer; ferrous ions and remaining metal ions will be precipitated and removed in the post-sedimentation tank.

[0005] However, the reduction alkali production system has a weak ability to treat high-acidity mine wastewater and urgently needs to be improved to improve the treatment effect of low pH, high iron, and high sulfate mine wastewater. Summary of the invention

[0006] In order to solve the above problems in the prior art, the present invention provides a mine wastewater treatment system and method for red mud-organic matter coupled reduction to produce alkali. Through the red mud-organic matter coupled reduction to produce alkali, on the one hand, the acidity load resistance is improved, and the treatment effect of acidic mine wastewater, especially low pH, high iron, and high sulfate mine wastewater, is improved; on the other hand, the number of water-stable large particle aggregates is increased, the conversion and fixation rate of nutrients such as C and N, and the ability of organic matter to resist rain erosion are increased, which can be used to repair the soil and realize the resource utilization of red mud.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A mine wastewater treatment system for red mud organic matter coupled reduction and alkali production, comprising:

[0009] Pre-sedimentation tank, reaction tank and post-sedimentation tank connected in sequence;

[0010] The reaction tank is filled with fillers, which include inorganic fillers and composite fillers. The inorganic fillers and composite fillers are filled in layers from bottom to top to form inorganic filler layers and composite filler layers.

[0011] The composite filler is formed by mixing biomass and red mud in a certain proportion and fermenting and composting, specifically: the biomass and red mud are uniformly mixed in a preset weight ratio; natural fermentation is performed for a preset first time; the compost is turned once every preset second time during composting, the overall moisture content is maintained at a preset moisture content value, the temperature is controlled within a preset temperature range during composting, and composting is completed after a preset total number of turnings.

[0012] Furthermore, the length of the pre-sedimentation tank is not less than 0.8 times the length of the reaction tank, the width of the pre-sedimentation tank is not less than 0.7 times the width of the reaction tank, and the depth of the pre-sedimentation tank is not less than 1 times the depth of the reaction tank;

[0013] The length of the rear sedimentation tank shall not be less than 1.5 times the length of the reaction tank, the width of the rear sedimentation tank shall not be less than 1.5 times the width of the reaction tank, and the depth shall not be less than 1.5 times the width of the reaction tank.

[0014] Furthermore, the mine wastewater to be treated enters the reaction pool to form a water layer, the water layer is above the composite filler layer, and the thickness of the water layer is not less than 60 cm; the thickness of the composite filler layer is 20-60 cm; the thickness of the inorganic filler layer is not less than 100 cm.

[0015] Furthermore, the inorganic filler is limestone, and the particle size of the limestone is 1 to 3 cm.

[0016] Furthermore, the reaction tank is provided with a flushing system, which includes an upper pipe and a lower pipe. The upper pipe is located in the middle of the inorganic filler layer. During operation, water is discharged from the upper pipe in an overflow manner. The lower pipe is located below the inorganic filler layer. When the inorganic filler layer is blocked and needs to be flushed, the sediment is flushed out from the lower pipe.

[0017] A method for treating mine wastewater by red mud organic matter coupled reduction to produce alkali, comprising the following steps:

[0018] Step S1: constructing the mine wastewater treatment system for red mud organic matter coupled reduction and alkali production;

[0019] Step S2: directing the mine wastewater to be treated to a pre-sedimentation tank, wherein the hydraulic retention time of the pre-sedimentation tank is 24-72 hours, and removing part of the trivalent iron ions in the form of iron hydrate;

[0020] Step S3: Lead the effluent from the pre-sedimentation tank to the reaction tank, where the hydraulic retention time is 48-120 hours to remove metal ions and sulfate ions;

[0021] Step S4: The effluent from the reaction tank is discharged into the post-sedimentation tank, and the sediment in the reaction tank is regularly flushed away. The hydraulic retention time in the post-sedimentation tank is 24-72 hours, and the trivalent iron ions are precipitated and removed.

[0022] Furthermore, the step S1 includes:

[0023] Step S101: excavating the pre-sedimentation tank, the reaction tank, and the post-sedimentation tank according to the designed dimensions, laying the lower layer pipeline at the bottom of the reaction tank, and setting a horizontal flushing port, the flushing port is provided with a ball valve, and the length of the lower layer pipeline is the same as the length of the reaction tank;

[0024] Step S102: fill the inorganic filler layer with half the designed thickness of limestone particles, then lay the upper pipe on the limestone particles, and then fill the other half of the thickness of limestone particles; the upper pipe is led out of the reaction tank and lifted to the same position as the designed water layer height by a three-way joint as an overflow port;

[0025] Step S103: laying a geotextile on the inorganic filler layer, and then filling the geotextile with a composite filler.

[0026] Furthermore, in step S103, the preparation process of the composite filler is:

[0027] The biomass and red mud are uniformly mixed in a weight ratio of 1:1-5:1, wherein the biomass includes animal excrement, wood chips, and straw;

[0028] The biomass and red mud mixture is taken out after a preset 3-month natural fermentation to mature;

[0029] The fermented biomass and red mud mixture is turned over every 6 days during the composting period. The overall moisture content is maintained at 45%-55%. The temperature is controlled in the range of 40℃ to 70℃ during the composting period. After a total of 5 turnings, the composting is completed.

[0030] A method for preparing a composting matrix by coupled reduction of red mud organic matter comprises the following steps:

[0031] The composite filler treated with mine wastewater is air-dried, and red mud is added to obtain a new organic red mud mixture, wherein the red mud mass accounts for 10% to 30% of the new organic mixture;

[0032] Mix well and spray water continuously, and carry out the decomposition reaction again for 5-10 days;

[0033] The organic red mud mixture after decomposition is turned over and drained, and 0.2%-0.4% compound bacterial agent is added to obtain a compost matrix.

[0034] A mine remediation method based on a compost matrix with coupled reduction of red mud organic matter:

[0035] The compost matrix is ​​treated by spraying water to make the moisture content of the pile reach 50%-60%. The aluminum and iron minerals precipitated in the post-sedimentation tank are added to the compost matrix at a ratio of 1:100 to 5:100 to form short-range ordered minerals to promote the formation of soil aggregates. After natural development for 1 to 3 months, it is used for the restoration of open-pit bauxite and other mining areas.

[0036] The main principles of the present invention are:

[0037] Biomass and red mud are mixed in a certain proportion, fermented and decomposed to form a composite filler, which is filled into a composite filler layer, and can create a reducing environment, reduce sulfate, and reduce trivalent iron to divalent iron;

[0038] When used, low pH, high iron, high sulfate mine water is led to the pre-sedimentation tank, where part of the trivalent iron ions will be removed in the form of ferric hydrate;

[0039] The effluent from the pre-sedimentation tank is then led to the top of the reaction tank through a pipe, and the inlet flow rate is determined according to the size of the reaction tank (the inlet water of the reaction tank is the effluent from the pre-sedimentation tank).

[0040] The influent water of the reaction pool first passes through the water layer, where part of the trivalent iron ions will be removed in the form of iron hydrates; then it passes through the composite filler layer, where the microorganisms will consume the dissolved oxygen to form a reducing environment, and the sulfate ions will be reduced and removed. The coupling of red mud and biomass can also improve the stability of the alkalinity improvement of the composite filler layer, so that part of the trivalent iron will be removed in the composite filler layer in the form of precipitation;

[0041] After that, it flows through the inorganic material layer composed of limestone. The dissolution of limestone increases the pH value of the water, causing metal ions such as iron and aluminum to precipitate and be removed;

[0042] Finally, the effluent from the reaction tank is discharged into the sedimentation tank, where the trivalent iron ions are further removed.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The present invention utilizes the principle of red mud and organic matter coupling reduction to produce alkali to treat acid mine wastewater, and prepares the red mud organic matter after treating the acid mine wastewater into a compost matrix to repair and improve the mine soil, with good treatment benefits, which are mainly reflected in:

[0045] 1. It can improve the alkali production rate of red mud, achieve the effect of slow-release alkali production, and combine the clay minerals and organic matter in the red mud to form an organic clay complex, effectively realizing the resource utilization of red mud.

[0046] 2. It can enhance the treatment effect of the reduction alkali production system and its ability to resist acid load and alkalinity. Red mud has high alkalinity and strong adsorption capacity, which can enhance the alkalinity enhancement capacity of the reduction alkali production system and the treatment effect of acid mine wastewater; red mud and compost can form a humic acid-humate buffer system, which increases the acid load resistance of the composite filler layer.

[0047] 3. The addition of red mud can increase the number of large particle aggregates in organic matter, improve the conversion and fixation rate of nutrients such as C and N, and the ability of organic matter to resist rain erosion. The composite filler that has treated mine wastewater can be prepared into a compost matrix, which can be directly used for planting plants. This overcomes the defect that red mud cannot be directly used for plant planting, achieves the effect of "treating waste with waste", fully reduces the cost of comprehensive management, and is very beneficial to mine restoration. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic diagram of the overall structure of a mine wastewater treatment system for red mud organic matter coupled reduction to produce alkali according to an embodiment of the present invention;

[0049] Figure 2 This is a flow chart of a method for treating mine wastewater by red mud organic matter coupled reduction to produce alkali according to an embodiment of the present invention;

[0050] Figure 3 A schematic diagram showing a comparison of changes in soil alkaline nitrogen content of different plants during a cultivation period in one embodiment of the present invention;

[0051] Figure 4 A schematic diagram showing a comparison of changes in soil available phosphorus content of different plants during a cultivation period in one embodiment of the present invention;

[0052] Figure 5 This is a schematic diagram comparing the changes in soil organic matter content of different plants during the cultivation period in one embodiment of the present invention.

[0053] In the figure:

[0054] 1-pre-sedimentation tank, 2-water layer, 3-water level line, 4-red mud, 5-composite filler layer, 6-inorganic filler layer, 7-upper pipeline, 8-lower pipeline, 9-ball valve, 10-reaction tank outlet, 11-post-sedimentation tank. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be fixedly connected, detachably connected, or integrated; it can be directly connected, or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0058] In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0059] In order to better understand the purpose, structure and function of the present invention, a detailed description is given below in conjunction with the accompanying drawings.

[0060] Example 1

[0061] like Figure 1 As shown, this embodiment provides a mine wastewater treatment system for red mud organic matter coupled reduction alkali production, comprising:

[0062] Pre-sedimentation tank, reaction tank and post-sedimentation tank connected in sequence;

[0063] The reaction tank is filled with fillers, which include inorganic fillers and composite fillers. The inorganic fillers and composite fillers are filled in layers from bottom to top to form inorganic filler layers and composite filler layers.

[0064] The composite filler is formed by mixing biomass and red mud in a certain proportion and fermenting and composting, specifically: the biomass and red mud are uniformly mixed in a preset weight ratio; natural fermentation is performed for a preset first time; the compost is turned once every preset second time during composting, the overall moisture content is maintained at a preset moisture content value, the temperature is controlled within a preset temperature range during composting, and composting is completed after a preset total number of turnings.

[0065] Furthermore, the length of the pre-sedimentation tank is not less than 0.8 times the length of the reaction tank, the width of the pre-sedimentation tank is not less than 0.7 times the width of the reaction tank, and the depth of the pre-sedimentation tank is not less than 1 times the depth of the reaction tank;

[0066] The length of the rear sedimentation tank shall not be less than 1.5 times the length of the reaction tank, the width of the rear sedimentation tank shall not be less than 1.5 times the width of the reaction tank, and the depth shall not be less than 1.5 times the width of the reaction tank.

[0067] Furthermore, the mine wastewater to be treated enters the reaction pool to form a water layer, the water layer is above the composite filler layer, and the thickness of the water layer is not less than 60 cm; the thickness of the composite filler layer is 20-60 cm; the thickness of the inorganic filler layer is not less than 100 cm.

[0068] Furthermore, the inorganic filler is limestone, and the particle size of the limestone is 1 to 3 cm.

[0069] Furthermore, the reaction tank is provided with a flushing system, which includes an upper pipe and a lower pipe. The upper pipe is located in the middle of the inorganic filler layer. During operation, water is discharged from the upper pipe in an overflow manner. The lower pipe is located below the inorganic filler layer. When the inorganic filler layer is blocked and needs to be flushed, the sediment is flushed out from the lower pipe.

[0070] Example 2

[0071] like Figure 2 As shown, this embodiment provides a method for treating mine wastewater by red mud organic matter coupled reduction to produce alkali, comprising the following steps:

[0072] Step S1: constructing the mine wastewater treatment system for red mud organic matter coupled reduction and alkali production;

[0073] Step S2: directing the mine wastewater to be treated to a pre-sedimentation tank, wherein the hydraulic retention time of the pre-sedimentation tank is 24-72 hours, and removing part of the trivalent iron ions in the form of iron hydrate;

[0074] Step S3: Lead the effluent from the pre-sedimentation tank to the reaction tank, where the hydraulic retention time is 48-120 hours to remove metal ions and sulfate ions;

[0075] Step S4: The effluent from the reaction tank is discharged into the post-sedimentation tank, and the sediment in the reaction tank is regularly flushed away. The hydraulic retention time in the post-sedimentation tank is 24-72 hours, and the trivalent iron ions are precipitated and removed.

[0076] Furthermore, the step S1 includes:

[0077] Step S101: excavating the pre-sedimentation tank, the reaction tank, and the post-sedimentation tank according to the designed dimensions, laying the lower layer pipeline at the bottom of the reaction tank, and setting a horizontal flushing port, the flushing port is provided with a ball valve, and the length of the lower layer pipeline is the same as the length of the reaction tank;

[0078] Step S102: fill the inorganic filler layer with half the designed thickness of limestone particles, then lay the upper pipe on the limestone particles, and then fill the other half of the thickness of limestone particles; the upper pipe is led out of the reaction tank and lifted to the same position as the designed water layer height by a three-way joint as an overflow port;

[0079] Step S103: laying a geotextile on the inorganic filler layer, and then filling the geotextile with a composite filler.

[0080] Furthermore, in step S103, the preparation process of the composite filler is:

[0081] The biomass and red mud are uniformly mixed in a weight ratio of 1:1-5:1, wherein the biomass includes animal excrement, wood chips, and straw;

[0082] The biomass and red mud mixture is taken out after a preset 3-month natural fermentation to mature;

[0083] The fermented biomass and red mud mixture is turned over every 6 days during the composting period. The overall moisture content is maintained at 45%-55%. The temperature is controlled in the range of 40℃ to 70℃ during the composting period. After a total of 5 turnings, the composting is completed.

[0084] Example 3

[0085] This embodiment provides a method for preparing a composting matrix by coupled reduction of red mud organic matter, comprising the following steps:

[0086] The composite filler treated with mine wastewater is air-dried, and red mud is added to obtain a new organic red mud mixture, wherein the red mud mass accounts for 10% to 30% of the new organic mixture;

[0087] Mix well and spray water continuously, and carry out the decomposition reaction again for 5-10 days;

[0088] The organic red mud mixture after decomposition is turned over and drained, and 0.2%-0.4% compound bacterial agent is added to obtain a compost matrix.

[0089] Example 4

[0090] This embodiment provides a mine remediation method based on a composting matrix of red mud organic matter coupled reduction:

[0091] The compost matrix is ​​treated by spraying water to make the moisture content of the pile reach 50%-60%. The aluminum and iron minerals precipitated in the post-sedimentation tank are added to the compost matrix at a ratio of 1:100 to 5:100 to form short-range ordered minerals to promote the formation of soil aggregates. After natural development for 1 to 3 months, it is used for the restoration of open-pit bauxite and other mining areas.

[0092] In this embodiment, the mine wastewater treatment system for red mud organic matter coupled reduction and alkali production also includes a mine remediation soil preparation area, and the treatment of the compost matrix is ​​completed in the preparation area.

[0093] Example 5

[0094] In this embodiment, the present invention is applied to a pilot site. After testing, it is confirmed that the present invention can improve the treatment effect of mine wastewater, and the compost matrix of red mud organic matter coupled reduction can be directly used for plant planting, as follows:

[0095] (1) Verification of mine wastewater treatment effect

[0096] A pilot site, covering an area of ​​about 400m 2 It consists of a pre-sedimentation tank, a reduction reaction tank, and an oxidation sedimentation tank. The water inlet is diverted by raising the water level of the acid mine drainage outlet river channel through a water barrier dam. The hydraulic retention time of the pre-sedimentation tank is 24 hours, the hydraulic retention time of the reaction tank is 72 hours, and the hydraulic retention time of the post-sedimentation tank is 72 hours. The operation time is 110 days.

[0097] The co-composting reduction alkali production reaction tank is designed to add organic matter with a mass ratio of 10% red mud as the organic matter layer during the composting stage, and the design size is: 3.37m×2.70m×1.83m. The designed water layer is 40cm thick, the organic layer is 25cm thick, and the alkali production medium layer is 100cm thick. The organic layer and the limestone layer are separated by geotextiles, and the outlet pipe divides the limestone layer into two layers. The hydraulic retention time is 72h.

[0098] The design size of the sedimentation tank after the co-composting reduction alkali production system is: 1.77m×3.58m×2.67m, and the hydraulic retention time is 72h.

[0099] The red mud-organic matter coupled reduction alkali production system has a strong ability to increase pH. The pH drop of the effluent during operation is small, and the alkalinity increase ability is stable. It has a strong ability to consume dissolved oxygen. The treatment effects on conventional indicators are shown in Table 1.

[0100] Table 1. Test results of conventional indicators of influent and effluent of red mud-organic matter coupled reduction alkali production system

[0101]

[0102] The red mud-organic matter coupled reduction alkali production system has a strong ability to remove iron and aluminum. The pre-sedimentation tank, wetland, and post-sedimentation tank can remove 21.36%, 61.23%, and 28.02% of total iron, 24.50%, 73.31%, and 24.36% of aluminum, and 2.95%, 14.38%, and 4.01% of sulfate, respectively, compared to their own influent. The specific treatment effects are shown in Table 2.

[0103] Table 2 Removal of metal ions and sulfate in the red mud-organic matter coupled reduction alkali production system

[0104]

[0105] The risk of heavy metal leaching during operation is low. The heavy metal indicators of the influent and the effluent of the reaction tank are tested. The heavy metal concentration limit in the total influent refers to the "Surface Water Environmental Quality Standard" (GB 3838-2002), and the heavy metal concentration limit in the effluent of the reaction tank refers to the "Comprehensive Sewage Discharge Standard" (GB 8978-1996). The specific corresponding limits are shown in Table 3, and the heavy metal concentrations in the effluent of the reaction tank are shown in Table 4. During the experiment, the concentration of heavy metals in the influent water changed greatly. The average concentration of Cu during the test was 0.51 mg / L, and the test index exceeded the concentration limit of Class V surface water on one day; the average detection concentration of Cd was 0.02 mg / L, and the detection index exceeded the concentration limit of Class V surface water on 5 days; the average detection concentration of Pb was 0.33 mg / L, all of which exceeded the concentration limit of Class V surface water; the average detection concentration of As was 0.03 mg / L, and one day exceeded the concentration limit of Class V surface water; all Zn was within the concentration limit of Class V surface water; the average leaching concentration of Cr was 0.570 mg / L, all of which exceeded the concentration limit of Class V surface water. After treatment in the reaction tank, all indicators were within the concentration limit of the "Comprehensive Wastewater Discharge Standard" (GB 8978-1996).

[0106] Table 3 Heavy metal leaching concentration limits

[0107]

[0108] Note: “-” indicates that this item is not included in the standard

[0109] Table 4 Heavy metal concentrations in influent and effluent from reaction tank

[0110]

[0111] (2) Verification of mine soil remediation effect

[0112] A pot experiment was conducted on the organic matter of the treated acid mine wastewater. The planting experiment uniformly used PVC pots (bottom inner diameter 10cm, upper diameter 15cm, height 10cm). The total mass of the mixed samples in the pots was 500g. Each treatment of the experiment was repeated 3 times, with a total of 63 pots. The soil cultivation time of the potted plants in the greenhouse was set to 8 weeks, and 30mL of water was sprayed every 2 days during the cultivation period. The physical and chemical properties of the improved matrix were measured every other week. Each time sampling was performed, mixed samples were taken from different locations as representative samples of the day.

[0113] The selected plants were Viola yedoensis, Dianthus and Lolium. The seeds with full grains and uniform size were selected and soaked in 10% H2O2 for 10 minutes for disinfection, and then washed with distilled water for use. The test matrix was the organic matter after the acid mine wastewater was treated. The organic matter was taken out, dried and crushed, and evenly mixed. The basic physical and chemical properties of the organic layer matrix are shown in Table 5.

[0114] Table 5 Basic physicochemical properties of the tested matrix

[0115]

[0116] Ryegrass is different from Crown Flower and Dianthus. Before 30 days, ryegrass has not yet matured and its root system is not well developed. After 30 days, ryegrass has basically grown and its root system is rapidly expanding. After the 7th week, it was observed that it formed a rich network of tissues in the soil matrix. In the soil of the ryegrass group, most of the N and P elements were absorbed and fixed by the plants, while only a small amount of N and P were lost through watering and leaching. And the roots filled the pot, and through interlacing and squeezing, it was easier to agglomerate the matrix particles.

[0117] Organic matter has different effects on different herbaceous plants ( Figure 3 , Table 6). During the entire cultivation period, except for the ryegrass treatment, the soil alkaline nitrogen of the other plant treatments generally showed a trend of first decreasing and then increasing. From 21 to 49 days of cultivation, the soil alkaline nitrogen content showed a significant upward trend with the increase of time, especially in the 3rd to 5th week, the increase rate was faster, and the increase rate was 283.6, 316.7, and 304.2 mg / kg, respectively, and the increase rate slowed down in the 5th to 7th week. In the ryegrass treatment, the alkaline nitrogen always maintained an upward trend, from 851.8 mg / kg in the first week to 987.7 mg / kg in the seventh week. The soil alkaline nitrogen content of the unco-composted group of crown flower and ryegrass group first increased and then decreased, and the alkaline nitrogen content in the seventh week was 797.3 and 833.9 mg / kg, respectively. The dianthus and Viola yedoensis groups always maintained an upward trend, and the alkaline nitrogen content in the seventh week increased to 886.8 and 852.1 mg / kg, as shown in Table 6.

[0118] Table 6 Changes in soil alkaline nitrogen content during the cultivation period

[0119]

[0120] Applying herbaceous plant material significantly reduced the available phosphorus level in the soil ( Figure 4 , Table 7). During the cultivation period, the soil available phosphorus content of the plant treatments showed a trend of first decreasing and then increasing. The decrease in rye was smaller and gradually remained stable in the later stage of the experiment, with the content of 38.2 mg / kg in the 7th week. The available phosphorus contents of the other crown flower, physalis, and dianthus treatments in the 7th week were 35.9, 32.1, and 36.5 mg / kg, as shown in Table 7.

[0121] Table 7 Changes in soil available phosphorus content during the cultivation period

[0122]

[0123] Planting herbaceous plants significantly increased soil organic matter levels (Table 8, Figure 5 ), the percentage of the crown flower group increased from 31.4% to 34.4%; the percentage of the Viola yedoensis group increased from 29.7% to 38.7%; the percentage of the Dianthus group increased from 29.2% to 33.7%; and the percentage of the Lolium group increased from 31.3% to 33.7%.

[0124] Table 8 Changes in soil organic matter content during the cultivation period

[0125]

[0126]

[0127] Ryegrass was the crop that grew best during the experiment. The cultivation medium mainly affects plant growth through the nutritional status of the plant and the harmful components in the medium. Available phosphorus exists in the soil and can be directly absorbed and utilized by plants, including all water-soluble phosphorus, part of the adsorbed phosphorus and organic phosphorus. Soil alkaline nitrogen includes water-soluble nitrogen, exchangeable nitrogen and easily hydrolyzed organic nitrogen in the soil. At the beginning of the experiment, the soil moisture content was high and the watering frequency was too frequent two weeks before germination. The soil environment had a strong denitrification effect, which reduced the soil nitrogen mineralization rate. As the potted experiment progressed, the mineralization effect gradually exceeded the biological fixation, and the alkaline nitrogen content began to increase gradually.

[0128] Ryegrass is different from Crown Flower and Dianthus. Before 30 days, ryegrass has not yet matured and its root system is not well developed. After 30 days, ryegrass has basically grown and its root system is rapidly expanding. After the 7th week, it was observed that it formed a rich network of tissues in the soil matrix. In the soil of the ryegrass group, most of the N and P elements were absorbed and fixed by the plants, while only a small amount of N and P were lost through watering and leaching. And the roots filled the pot, and through interlacing and squeezing, it was easier to agglomerate the matrix particles.

[0129] The composite filler used to treat acid mine wastewater is used to prepare a compost matrix through the method of the present invention, and plants can be directly planted therein, so the compost matrix can be widely used in mine soil restoration.

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A mine wastewater treatment system for red mud organic matter coupled reduction and alkali production, characterized in that: include: Pre-sedimentation tank, reaction tank and post-sedimentation tank connected in sequence; The reaction tank is filled with fillers, which include inorganic fillers and composite fillers. The inorganic fillers and composite fillers are filled in layers from bottom to top to form inorganic filler layers and composite filler layers. The composite filler is formed by mixing biomass and red mud in a certain proportion and fermenting and composting, specifically: the biomass and red mud are uniformly mixed in a preset weight ratio; natural fermentation is performed for a preset first time; the compost is turned once every preset second time during composting, the overall moisture content is maintained at a preset moisture content value, the temperature is controlled within a preset temperature range during composting, and composting is completed after a preset total number of turnings.

2. The mine wastewater treatment system for red mud organic matter coupled reduction and alkali production as claimed in claim 1 is characterized by: The length of the pre-sedimentation tank shall not be less than 0.8 times the length of the reaction tank, the width of the pre-sedimentation tank shall not be less than 0.7 times the width of the reaction tank, and the depth of the pre-sedimentation tank shall not be less than 1 times the depth of the reaction tank; The length of the rear sedimentation tank shall not be less than 1.5 times the length of the reaction tank, the width of the rear sedimentation tank shall not be less than 1.5 times the width of the reaction tank, and the depth shall not be less than 1.5 times the width of the reaction tank.

3. The mine wastewater treatment system for red mud organic matter coupled reduction and alkali production according to claim 1 is characterized in that: The mine wastewater to be treated enters the reaction pool to form a water layer, which is above the composite filler layer and has a thickness of not less than 60 cm; the composite filler layer has a thickness of 20-60 cm; and the inorganic filler layer has a thickness of not less than 100 cm.

4. The mine wastewater treatment system for red mud organic matter coupled reduction and alkali production according to claim 1 is characterized in that: The inorganic filler is limestone, and the particle size of the limestone is 1 to 3 cm.

5. The mine wastewater treatment system for red mud organic matter coupled reduction and alkali production according to claim 1 is characterized in that: The reaction tank is provided with a flushing system, which includes an upper pipe and a lower pipe. The upper pipe is located in the middle of the inorganic filler layer. During operation, water is discharged from the upper pipe in an overflow manner. The lower pipe is located below the inorganic filler layer. When the inorganic filler layer is blocked and needs to be flushed, the sediment is flushed out from the lower pipe.

6. A method for treating mine wastewater by coupling red mud organic matter reduction to produce alkali, characterized in that: The steps include: Step S1: constructing a mine wastewater treatment system for red mud organic matter coupled reduction and alkali production as described in any one of claims 1 to 5; Step S2: directing the mine wastewater to be treated to a pre-sedimentation tank, wherein the hydraulic retention time of the pre-sedimentation tank is 24-72 hours, and removing part of the trivalent iron ions in the form of iron hydrate; Step S3: Lead the effluent from the pre-sedimentation tank to the reaction tank, where the hydraulic retention time is 48-120 hours to remove metal ions and sulfate ions; Step S4: The effluent from the reaction tank is discharged into the post-sedimentation tank, and the sediment in the reaction tank is regularly flushed away. The hydraulic retention time in the post-sedimentation tank is 24-72 hours, and the trivalent iron ions are precipitated and removed.

7. The method for treating mining wastewater by red mud organic matter coupled reduction to produce alkali as claimed in claim 6, characterized in that: The step S1 includes: Step S101: excavating the pre-sedimentation tank, the reaction tank, and the post-sedimentation tank according to the designed dimensions, laying the lower layer pipeline at the bottom of the reaction tank, and setting a horizontal flushing port, the flushing port is provided with a ball valve, and the length of the lower layer pipeline is the same as the length of the reaction tank; Step S102: fill the inorganic filler layer with half the designed thickness of limestone particles, then lay the upper pipe on the limestone particles, and then fill the other half of the thickness of limestone particles; the upper pipe is led out of the reaction tank and lifted to the same position as the designed water layer height by a three-way joint as an overflow port; Step S103: laying a geotextile on the inorganic filler layer, and then filling the geotextile with a composite filler.

8. The method for treating mining wastewater by red mud organic matter coupled reduction to produce alkali as claimed in claim 7, characterized in that: In step S103, the preparation process of the composite filler is as follows: The biomass and red mud are uniformly mixed in a weight ratio of 1:1-5:1, wherein the biomass includes animal excrement, wood chips, and straw; The biomass and red mud mixture is taken out after a preset 3-month natural fermentation to mature; The fermented biomass and red mud mixture is turned over every 6 days during the composting period. The overall moisture content is maintained at 45%-55%. The temperature is controlled in the range of 40℃ to 70℃ during the composting period. After a total of 5 turnings, the composting is completed.

9. A method for preparing a compost matrix by coupled reduction of red mud organic matter, characterized in that: The steps include: Air-drying the composite filler as claimed in claim 8 that has been used to treat mining wastewater, and supplementing with red mud to obtain a new organic red mud mixture, wherein the mass of the red mud accounts for 10% to 30% of the new organic mixture; Mix well and spray water continuously, and carry out the decomposition reaction again for 5-10 days; The organic red mud mixture after decomposition is turned over and drained, and 0.2%-0.4% compound bacterial agent is added to obtain a compost matrix.

10. A mine remediation method based on a compost matrix with coupled reduction of red mud organic matter: The composting matrix as claimed in claim 9 is treated by spraying with water so that the moisture content of the compost reaches 50%-60%; the aluminum-iron minerals precipitated in the rear sedimentation tank are added to the composting matrix at a ratio of 1:100 to 5:100 to form short-range ordered minerals to promote the formation of soil aggregates, and after natural development for 1 to 3 months, the composting matrix is ​​used for the restoration of open-pit bauxite and other mining areas.

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