Mushroom carbon composite filler, constructed wetland-microbial electrochemical coupling system and method for treating acid mine wastewater by using constructed wetland-microbial electrochemical coupling system

Abstract

The invention discloses a fungus carbon composite filler, an artificial wetland-microbial electrochemical coupling system and a method for treating acid mine wastewater by using the artificial wetland-microbial electrochemical coupling system. The system comprises an artificial wetland device and a microbial electrochemical device. The constructed wetland consists of wetland plants, gravels, pyrite and a bacterial carbon composite filler containing zero-valent iron; the microbial electrochemical device comprises an air cathode, a cathode, an anode, an external resistor and a solar power supply device. The bacterial carbon composite filler containing zero-valent iron is formed by compounding zero-valent iron biochar prepared by co-pyrolysis of AMD sludge and an invasive species solidago canadensis and SRB. According to the system, heavy metal fixation, sulfate reduction and pH regulation are realized through the synergistic effect of the wetland plants, the charcoal composite filler and the electrochemical device. The device has the advantages of high treatment efficiency, high stability, low operation cost, environmental friendliness and the like, and is suitable for engineering application of AMD treatment in mining areas.

Description

Technical Field

[0001] This invention belongs to the technical field of mining area environmental protection and relates to a biochar composite filler, a constructed wetland-microbial electrochemical coupling system, and a method for treating acidic mine drainage. Specifically, a biochar composite filler matrix, prepared by combining biochar containing zero-valent iron with sulfate-reducing bacteria, is used to enhance the synergistic removal of metal ions and sulfate by the constructed wetland-microbial electrochemical system, thereby achieving efficient treatment of acidic mine drainage. Background Art

[0002] Acid mine drainage (AMD) is wastewater generated by mining, smelting and other activities. It usually has a low pH value, high concentrations of heavy metal ions and other harmful substances. Its discharge causes serious pollution to the environment and aquatic ecosystems, affecting water quality and ecological balance, and posing a threat to surrounding organisms. Traditional acid mine drainage treatment methods, such as chemical precipitation and neutralization, can effectively remove some pollutants, but they have problems such as high cost, secondary pollution and low treatment efficiency. Seeking a low-cost, efficient and stable technical method to treat AMD has become an urgent problem to be solved.

[0003] Constructed wetland technology, as a relatively green and sustainable wastewater treatment technology, has garnered widespread attention in recent years. Constructed wetlands can remove pollutants from water through microbial degradation and adsorption, and are particularly effective in removing organic pollutants and nitrogen and phosphorus. However, traditional constructed wetland systems are limited in their treatment efficiency and long-term stability for acid mine drainage (AMD) due to factors such as weak substrate adsorption and insufficient plant immobilization capacity. This poses challenges, leaving room for further improvement.

[0004] In recent years, microbial electrochemical technology, as an emerging water treatment method, has demonstrated significant potential for improving pollutant removal efficiency and enhancing system stability. Microbial electrochemical systems utilize electron transfer between electrodes and microorganisms to promote pollutant removal through electrochemical processes. Combining microbial electrochemical technology with constructed wetland systems can effectively enhance the removal of harmful substances from wastewater, demonstrating particularly good adaptability and removal effectiveness in acidic environments.

[0005] As an adsorption material with high specific surface area and rich pore structure, biochar has been widely used in the field of environmental governance in recent years. Using biochar as a matrix for artificial wetlands can provide a more suitable growth environment for wetland plants by improving the matrix porosity, water retention and nutrient retention capacity. At the same time, it can improve the system's removal efficiency of pollutants through adsorption, complexation and microbial growth promotion effects. However, traditional biochar still has certain limitations in the treatment of acid mine drainage (AMD), mainly manifested in its low affinity for Fe in a strong acidic environment.3+ 、Mn 2+ The adsorption performance of heavy metals such as iodine is reduced, and there is a lack of active sites to promote the transformation and precipitation of metal ions. The pH regulation ability is weak, which affects its application effect in complex polluted environments. Summary of the Invention

[0006] In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a bacterial carbon composite filler and a preparation method thereof and its application as a filler matrix in the treatment of acidic mine wastewater.

[0007] Another object of the present invention is to provide an artificial wetland-microorganism electrochemical coupling system containing the above-mentioned bacterial carbon composite filler.

[0008] Another object of the present invention is to provide the above-mentioned method for treating acid mine drainage based on the artificial wetland-microorganism electrochemical coupling system.

[0009] The present invention realizes good control of AMD pollution generated in mining areas and resource utilization of hazardous wastes.

[0010] The purpose of the present invention is achieved through the following technical solutions:

[0011] A method for preparing a bacterial carbon composite filler comprises the following steps:

[0012] (1) Acid mine drainage (AMD) sludge and Solidago canadensis stem powder were fully mixed and then co-pyrolyzed to obtain biochar containing zero-valent iron;

[0013] (2) After sterilizing the culture medium, add the diluted acid mine drainage (AMD) sludge solution and culture it at a constant temperature under anaerobic conditions until the liquid turns black and has a rotten egg smell, thereby enriching the sulfate-reducing bacteria (SRB) culture liquid;

[0014] (3) adding the biochar material containing zero-valent iron in step (1) to the biological fermentation liquid, mixing, sterilizing and cooling to room temperature, adding the sulfate-reducing bacteria (SRB) bacterial liquid in step (2) and performing constant temperature adsorption and fixation, sieving, rinsing, and obtaining a biochar composite filler containing zero-valent iron.

[0015] Preferably, the weight ratio of the acid mine drainage (AMD) sludge to the Solidago canadensis stem powder in step (1) is 2 to 3:1.

[0016] Preferably, the co-pyrolysis temperature in step (1) is 800-900° C. and the time is 2-4 hours.

[0017] Preferably, the co-pyrolysis in step (1) is carried out in an inert gas atmosphere, and the inert gas is at least one of nitrogen, argon and helium.

[0018] The preparation of the biochar material containing zero-valent iron in step (1) is prepared by co-pyrolysis of iron-rich AMD sludge and the invasive species Solidago canadensis stems. 2+ / Fe 3+ , which can be reduced to zero-valent iron during high-temperature pyrolysis. The incorporation of Canada goldenrod stems can increase the specific surface area and pore volume of biochar, thereby enhancing the adsorption performance of pollutants.

[0019] Preferably, the culture medium in step (2) is composed of K2HPO4, MgSO4·7H2O, Na2SO4, CaCl2·2H2O, yeast extract, DL-Na-lactate, (NH4)2SO4, vitamin B complex and trace element solution in a concentration ratio of 0.5-1g / L: 1.5-2.5g / L: 1-1.5g / L: 2-2.5g / L: 1-2g / L: 2-3g / L: 0.4-0.6g / L: 0.03-0.07g / L: 0.5-1.5mL / L. The yeast extract is LP0021B produced by Oxoid; the DL-Na-lactate is S817880 produced by Maclean; the vitamin B complex is prepared by mixing vitamins B1, B2, B3, B5, B6, B9 and B12 in a ratio of 80-120 mg / g, 80-120 mg / g, 80-120 mg / g, 80-120 mg / g, 15-30 mg / g and 0.5-2 mg / g; the trace element solution contains Fe 2+ 、Mn 2+ 、Zn 2+ 、Co 2+ The concentrations were 1.5-3 mg / L, 0.3-0.7 mg / L, 0.05-2 mg / L and 0.05-0.2 mg / L respectively.

[0020] Preferably, the sterilization method in step (2) is high temperature and high pressure sterilization, specifically, placing the culture medium in a sterilizer and setting the sterilization conditions to 121°C, 1.05-1.1 kg / cm 2 , the sterilization time is set to 20 to 30 minutes.

[0021] Preferably, the acid mine drainage (AMD) sludge dilution solution in step (2) is obtained by mixing acid mine drainage (AMD) sludge and water in a mass ratio of 1-2:4-10; a more preferred mass ratio is 1:4.

[0022] Preferably, the volume ratio of the culture medium to the acid mine drainage (AMD) sludge dilution solution in step (2) is 20-40:2-5.

[0023] Preferably, the constant temperature culture in step (2) is 30-35° C. and the time is 6-7 days.

[0024] Preferably, the biological fermentation liquid in step (3) is prepared by mixing biogas slurry produced by fermentation of rice straw and pig manure, which are agricultural waste, with water, and has a pH of 7.11-7.52 and a COD content of 8324-10268 mg / L.

[0025] Preferably, in step (3), the ratio of the mass of the biochar material containing zero-valent iron, the volume of the biological fermentation liquid, and the volume of the sulfate-reducing bacteria (SRB) liquid is 10-20 g: 100-250 mL: 5-10 mL.

[0026] Preferably, the sterilization in step (3) refers to high-temperature sterilization, the temperature is 121° C., and the sterilization time is set to 20 to 30 minutes.

[0027] Preferably, the constant temperature in step (3) is 30-35°C.

[0028] Preferably, the constant temperature adsorption fixation time in step (3) is 8 to 12 hours.

[0029] Preferably, the constant temperature adsorption in step (3) is carried out in a shaking table with a rotation speed of 150 to 200 r / min.

[0030] Preferably, the sieving in step (3) refers to sieving through a 100-200 mesh sieve.

[0031] Preferably, the flushing in step (3) refers to flushing with sterile water.

[0032] The present invention provides a bacterial carbon composite filler prepared by the above preparation method.

[0033] The present invention provides application of the above-mentioned bacterial carbon composite filler in treating acidic mine wastewater.

[0034] The present invention provides an artificial wetland-microorganism electrochemical coupling system for efficiently treating AMD, comprising an artificial wetland device and a microbial electrochemical device;

[0035] The artificial wetland device includes a matrix and wetland plants located on the surface of the matrix, wherein the matrix is ​​composed of an upper gravel layer, a middle pyrite layer, a lower layer of the above-mentioned bacterial carbon composite filler layer containing zero-valent iron, and a bottom gravel support layer from top to bottom;

[0036] The microbial electrochemical device comprises an air cathode, a cathode, an anode and a solar power supply device;

[0037] The air cathode is located on the surface of the artificial wetland matrix and is in contact with the air;

[0038] The cathode is located in the middle layer of pyrite in the artificial wetland matrix;

[0039] The anode is located in the lower layer of the artificial wetland matrix in the bacterial carbon composite filler containing zero-valent iron;

[0040] The solar power supply device is located outside the artificial wetland device;

[0041] One end of the anode is connected to the air cathode, and the other end is connected to the solar power supply device and the cathode in sequence.

[0042] Preferably, the wetland plant located on the surface of the substrate is at least one of sedge, water plantain, calamus, canna and reed.

[0043] Preferably, the particle size of the gravel is 5 to 10 mm.

[0044] Preferably, the layer height proportions of the upper gravel layer, the middle pyrite layer, the lower carbon composite filler layer containing zero-valent iron and the bottom supporting gravel layer are 15-25%, 20-30%, 30-50% and 10-15% respectively.

[0045] Gravel with a particle size of 5-10 mm was selected as the upper and lower support fillers of the microbial electrochemical device to provide a favorable microbial habitat and reduce hydraulic load. A pyrite filler layer was placed in the middle layer of the constructed wetland device to enhance electron transfer. A bacterial carbon composite filler containing zero-valent iron was used as the lower filler, releasing electrons in an anaerobic environment and promoting the redox reaction in the system.

[0046] Preferably, the microbial electrochemical device further comprises a first external resistor and a second external resistor; the first external resistor is arranged between the anode and the air cathode, and the second external resistor is arranged between the solar power supply device and the cathode.

[0047] Preferably, the connections are all made via insulated copper wires.

[0048] Preferably, the air cathode, cathode and anode are all composed of graphite particles wrapped in a stainless steel mesh; the stainless steel mesh has a mesh size of 5 to 10; and the particle size of the graphite particles is 1 to 2.5 mm.

[0049] Preferably, the solar power supply device includes a solar photovoltaic panel, a battery and a voltage conversion module.

[0050] The air cathode of the microbial electrochemical device is located on the surface of the constructed wetland matrix, above the gravel packing layer, in contact with air to improve oxygen transfer efficiency and promote the oxygen reduction reaction. The cathode is located in the pyrite packing layer to enhance electron transfer and promote the cathodic reduction reaction. The anode is located in the bacterial carbon composite packing layer containing zero-valent iron to provide an electron donor and promote the microbial-mediated oxidation reaction.

[0051] Preferably, the artificial wetland device further comprises an inlet pipe and an outlet pipe; the inlet pipe is arranged in the bottom supporting gravel layer, and the outlet pipe is arranged in the upper gravel layer.

[0052] More preferably, the water inlet pipe is also connected to a water inlet pump and a water inlet solenoid valve.

[0053] The present invention provides a method for treating acid mine wastewater based on the above-mentioned artificial wetland-microorganism electrochemical coupling system, comprising the following steps:

[0054] After removing floating and suspended solids from acid mine drainage (AMD), it enters the constructed wetland-microbial electrochemical coupling system through the inlet pipe and undergoes retention treatment before being discharged through the outlet pipe.

[0055] Preferably, the residence time of the acid mine wastewater in the artificial wetland-microorganism electrochemical coupling system is 18 to 48 hours.

[0056] Preferably, the acid mine wastewater is treated by the artificial wetland-microorganism electrochemical coupling system and discharged into the sedimentation tank through the outlet pipe. The effluent that meets the standards is directly discharged, and the effluent that does not meet the standards enters the artificial wetland-microorganism electrochemical coupling system again for secondary treatment until the effluent water quality meets the standards.

[0057] After acid mine drainage (AMD) enters the artificial wetland-microbial electrochemical coupling system, the wetland plant roots and the microbial symbiotic system can effectively adsorb and fix heavy metals. The gravel, pyrite and the bacterial carbon composite filler containing zero-valent iron in the matrix synergistically remove pollutants. The bottom gravel support layer provides a habitat for microorganisms, adsorbs and intercepts pollutants, and reduces hydraulic shock loads. The middle pyrite layer can enhance electron transfer and promote the redox conversion of heavy metal ions and sulfates to achieve a fixation effect. The bacterial carbon composite filler containing zero-valent iron serves as the anode layer matrix, which not only provides a carbon source for microbial growth and reproduction, but also acts as an electron donor to accelerate the microbial-driven oxidation reaction. The microbial electrochemical device drives the electrochemical reaction. In the anode area, the bacterial carbon composite filler promotes electron release, oxidizes organic matter and Fe 2+The cathode region promotes electron acceptance through the air cathode or cathode. Sulfate, through the combined action of zero-valent iron and electrons provided by the electrochemical system, undergoes biological reduction by sulfate-reducing bacteria and a cathode electrochemical reaction to generate sulfide, which then forms an insoluble precipitate with metal ions. Furthermore, the microbial communities at the anode and cathode accelerate electron flow through extracellular electron transfer mechanisms, strengthening the redox cycle of pollutants, achieving heavy metal precipitation and fixation, sulfate reduction, and pH regulation, thereby enhancing the system's ability to treat AMD.

[0058] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0059] 1) The AMD treatment effect is good, the performance is efficient and stable, and the implementation and application cost is low. It is suitable for engineering application of AMD treatment in mining areas or improvement of existing projects.

[0060] 2) The present invention utilizes AMD sludge and the stems of the invasive species Solidago canadensis to prepare a biochar material containing zero-valent iron, which is then compounded with sulfate-reducing bacteria to form a biochar composite filler matrix. This is used to enhance the removal of pollutants from AMD by the constructed wetland-microbial electrochemical system, effectively achieving high-value utilization of toxic and hazardous waste. The constructed wetland-microbial electrochemical system utilizes only clean solar energy during operation, resulting in low economic costs and good environmental benefits. The implementation of the present invention enables efficient treatment of AMD and can effectively alleviate environmental pollution caused by the mining process. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 Schematic diagram of a zero-valent iron biochar-enhanced constructed wetland electrochemical system for efficient treatment of AMD wastewater:

[0062] In the figure: 1-wetland plants, 2-gravel filler layer, 3-pyrite filler layer, 4-composite bacterial carbon filler layer containing zero-valent iron, 5-gravel support layer, 6-solenoid valve, 7-water inlet pipe, 8-water inlet pump, 9-water outlet pipe, 10-air cathode, 11-cathode, 12-first external resistor, 13-insulated copper wire 1, 14-anode, 15-insulated copper wire 2, 16-second external resistor, 17-solar power supply device.

[0063] Figure 2 This is the SEM-EDS image of biochar containing zero-valent iron.

[0064] Figure 3 This is the XRD pattern of biochar containing zero-valent iron.

[0065] Figure 4 The pH changes of the acid mine drainage water after treatment in Example 3 and Comparative Examples 1 to 3 are shown.

[0066] Figure 5The metal removal rates in acid mine wastewater are shown in Example 3 and Comparative Examples 1 to 3.

[0067] Figure 6 The COD removal rates in acid mine wastewater are shown in Example 3 and Comparative Examples 1 to 3.

[0068] Figure 7 The removal rates of sulfate in acid mine wastewater in Example 3 and Comparative Examples 1 to 3 are shown. DETAILED DESCRIPTION

[0069] The present invention will be described in further detail below with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

[0070] In the examples of the present invention, if the specific conditions are not specified, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. All raw materials and reagents used without specifying the manufacturer are conventional products that can be purchased from the market.

[0071] Example 1

[0072] In view of the problems of limited adsorption capacity, insufficient chemical conversion performance and weak pH buffering capacity in the process of treating AMD caused by existing traditional biochar, the present invention provides a method for preparing a biochar composite filler containing zero-valent iron.

[0073] The preparation method of the bacterial carbon composite filler containing zero-valent iron comprises: preparation of biochar containing zero-valent iron, enrichment and purification of SRB, and synthesis of the bacterial carbon composite filler containing zero-valent iron.

[0074] 1) Preparation of zero-valent iron-containing biochar: The stems of the invasive species Solidago canadensis were collected, dried in an oven to constant weight, and then crushed. AMD sludge from a copper mining area in central China and Solidago canadensis stem powder were mixed in a weight ratio of 2:1 and co-pyrolyzed at 900°C in a nitrogen atmosphere for 2 hours to obtain a biochar containing zero-valent iron.

[0075] 2) SRB enrichment and purification: 5 g of AMD sediment sample from a copper mining area in the central region was placed in a 150 mL conical flask, and 20 mL of ultrapure water was added to obtain a dilution solution. The culture medium was heated at 121 ° C and 1.05 kg / cm 2 Sterilize under high temperature and high pressure conditions for 30 minutes, cool to room temperature, add 5 mL of sediment dilution to 40 mL of culture medium, and then culture in a 30°C constant temperature incubator under anaerobic conditions for 7 days. The liquid in the conical flask turns black and has a strong rotten egg smell, indicating that SRB is successfully enriched.

[0076] SRB culture medium contains 0.6g / L K2HPO4, 1.8g / L MgSO4·7H2O, 1.2g / L Na2SO4, 2.2g / L CaCl2·2H2O, 1.5g / L yeast extract, 2.5g / L DL-Na-lactate, 0.5g / L (NH4)2SO4, 0.05g / L vitamin B complex and 1mL / L trace element solution. The yeast extract is LP0021B produced by Oxoid; DL-Na-lactate is S817880 produced by Maclean; vitamin B complex is prepared by vitamin B1, B2, B3, B5, B6, B9 and B12 produced by Maclean, with the preparation ratios of 100mg / g, 100mg / g, 100mg / g, 100mg / g, 20mg / g and 1mg / g respectively. The trace element solution contains Fe 2+ 、Mn 2+ 、Zn 2+ 、Co 2+ The concentrations were 2 mg / L, 0.5 mg / L, 0.1 mg / L and 0.1 mg / L respectively.

[0077] 3) Synthesis of a Zero-Valent Iron-Containing Biochar Composite Filler: 20 g of zero-valent iron-containing biochar was added to 250 mL of fermentation broth (a mixture of fermented biogas slurry (rice straw and pig manure) with tap water, pH 7.46, and COD content 9430 mg / L). The mixture was sterilized at 121°C for 30 minutes and then cooled to room temperature. After addition of 10 mL of SRB bacterial solution, the mixture was placed in a constant-temperature shaker at 30°C and 180 rpm for 10 hours. The mixture was then passed through a 200-mesh sieve and the material on the sieve was repeatedly rinsed with sterile water to obtain the zero-valent iron-containing biochar composite filler.

[0078] Figure 2 This is a SEM-EDS image of biochar containing zero-valent iron. The SEM image shows a coordinated distribution of plant fiber skeletons and mineral particles within the sample, with the particles adhering to the surface and pores of the biochar skeleton. This indicates that the Solidago canadensis stems and AMD sludge were uniformly mixed before pyrolysis and achieved a good composite during the pyrolysis process. EDS results indicate that the sample surface contains significant amounts of Si, Fe, and S, further confirming the good mixing of the two components.

[0079] Figure 3 The XRD pattern of biochar containing zero-valent iron shows that the main crystalline phase in biochar is Fe 0 , FeS and SiO2, indicating that the raw material components successfully formed a multiphase inorganic structure containing zero-valent iron during the pyrolysis process.

[0080] Example 2

[0081] In view of the problems of high cost, secondary pollution and low treatment efficiency in the existing technology for treating acid mine drainage, the present invention provides an artificial wetland-microorganism electrochemical coupling system based on bacterial carbon composite filler. Figure 1 As shown, it consists of an artificial wetland device and a microbial electrochemical device. The bacterial carbon composite filler containing zero-valent iron is used as the anode filler in the microbial electrochemical device to enhance the removal effect of this system on heavy metals and sulfates in acidic mine drainage.

[0082] The constructed wetland device includes a substrate and wetland plants 1 located on the substrate's surface. These plants include sedges, calamus, and reeds, which are capable of adsorbing and fixing heavy metals. From top to bottom, the substrate consists of an upper gravel layer 2, a middle pyrite layer 3, a lower layer of a microbial carbon composite filler containing zero-valent iron 4, and a bottom supporting gravel layer 5. The pyrite serves as the cathode filler in the middle layer, while the microbial carbon composite filler containing zero-valent iron serves as the anode filler in the microbial electrolysis cell. The gravel has a particle size of 5 to 10 mm.

[0083] The layer heights of the upper gravel layer, the middle pyrite layer, the lower carbon composite filler layer containing zero-valent iron, and the bottom supporting gravel layer account for 20%, 25%, 40% and 15% respectively.

[0084] The artificial wetland device also includes a water inlet pump 8, a water inlet pipe 7, a water inlet solenoid valve 6 and an upper water outlet pipe 9, wherein the water inlet pipe 7 is arranged in the bottom supporting layer gravel layer, and the water outlet pipe 9 is arranged in the upper gravel layer.

[0085] The microbial electrochemical device includes an anode 14, an air cathode 10, a cathode 11, a first external resistor 12, a second external resistor 16, insulated copper electrodes 13 and 15, and a solar power supply 17. Anode 14 is located in a composite filler containing zero-valent iron (ZVI) in the lower layer of the constructed wetland matrix. Air cathode 10 is located on its surface, exposed to air. Cathode 11 is located in the pyrite layer of the constructed wetland matrix. The first external resistor 12, the second external resistor 16, and the solar power supply 17 are located outside the constructed wetland device. The anode, cathode, and air cathode are all composed of graphite particles (1-2.5 mm) encased in a 5-mesh stainless steel mesh. The solar power supply includes a solar photovoltaic panel, a battery, and a voltage conversion module (the solar photovoltaic panel provides power, the battery stores power, and the voltage conversion module stabilizes the current). An external circuit of insulated copper wire 15 provides a voltage of 1-2.5 V to the device. An insulated copper wire 15 is used as an external circuit to connect the cathode 11, the anode 14, the second external resistor 16 (1000Ω) and the solar power supply device 17, and an insulated copper wire 12 is used as an external circuit to connect the air cathode 10, the anode 14 and the first external resistor 12 (1000Ω).

[0086] Example 3

[0087] An application method of an artificial wetland-microorganism electrochemical coupling system based on a bacterial carbon composite filler for efficiently treating acid mine drainage, and the method is implemented using the artificial wetland-microorganism electrochemical coupling system based on a bacterial carbon composite filler described in Example 2. Before entering the device, the acid mine drainage water from a copper mining area in the central region is first concentrated in a sedimentation tank in front of the water inlet to remove floating objects and suspended matter. In this system, wastewater (AMD) is continuously pumped in from the bottom of the device by an inlet pump, the water inlet solenoid valve is opened, and the water inlet volume is controlled by a flow meter to ensure that the water inlet flow is stable. During operation, the system maintains a continuous flow state, and water continuously enters and is treated by the artificial wetland device and the microbial electrochemical device. The hydraulic retention time (HRT) of the system is set to 48 hours to ensure that the wastewater has sufficient residence time in the system to achieve a sufficient treatment effect. The treated wastewater is continuously discharged through the upper outlet pipe. After the device has been running stably for 20 days, it will be monitored continuously for 10 days. The treated wastewater that meets the standards will be directly discharged into the discharge system; the treated wastewater that does not meet the standards will be pumped back to the sedimentation tank and treated again by the artificial wetland-microbial electrochemical coupling system based on bacterial carbon composite filler to ensure that the final effluent water quality is stable and meets the discharge standards.

[0088] Comparative Example 1

[0089] In order to verify the performance advantages of the zero-valent iron-containing bacterial carbon composite filler described in the present invention in the treatment of acidic mine wastewater, the sludge carbon prepared by pyrolysis of AMD sludge and the composite material obtained by SRB were used as filler to construct an artificial wetland-microbial electrochemical system for comparative analysis with the system described in the present invention.

[0090] The sludge charcoal was prepared by pyrolyzing AMD sludge at 900°C for 2 hours in a nitrogen atmosphere. SRB was enriched and purified using the method of step 2) of Example 1, and then the sludge charcoal and SRB were compounded using the method of step 3) of Example 2 to prepare a sludge charcoal-bacteria composite filler.

[0091] The bacterial carbon composite filler containing zero-valent iron in Example 2 was replaced with a sludge carbon bacteria composite filler and an artificial wetland-microorganism electrochemical coupling system was constructed using the construction method in Example 2. The system was then tested in an application according to Example 3.

[0092] Table 1

[0093]

[0094] As can be seen from Table 1, the biochar containing zero-valent iron prepared by co-pyrolysis of Canada thistle stems and AMD sludge in Example 1 was used to construct a constructed wetland-microbial electrochemical coupling system for treating acidic mine wastewater, and the pH was increased by 2.8 units compared with the sludge biochar in Comparative Example 1. The specific surface area and pore volume of the biochar in Example 1 were also increased by 111.33% and 189.29%, respectively, compared with the sludge biochar in Comparative Example 1.

[0095] Comparative Example 2

[0096] In order to further verify the performance advantage of the bacterial carbon composite filler containing zero-valent iron in the present invention in treating acid mine wastewater, an artificial wetland-microbial electrochemical system with pyrite as the functional filler was set up as a comparative example.

[0097] The bacterial carbon composite filler containing zero-valent iron was replaced with pyrite and a constructed wetland-microorganism electrochemical coupling system was constructed using the construction method of Example 2. The constructed wetland matrix consisted of an upper gravel layer, a middle and lower pyrite layer, and a bottom supporting gravel layer from top to bottom.

[0098] The upper gravel layer, the middle and lower pyrite layer, and the bottom supporting gravel layer account for 20%, 65%, and 15% of the layer height respectively.

[0099] Then, the system is tested for application according to Example 3.

[0100] Comparative Example 3

[0101] In order to further illustrate the treatment efficiency of the artificial wetland-microbial electrochemical coupling system of the present invention, an ordinary artificial wetland system without a microbial electrochemical device was set as a comparative example.

[0102] The constructed wetland system was constructed according to the method described in Example 2, including a substrate and wetland plants located on the substrate surface. The wetland plants used were sedge, calamus, and reed. The substrate consisted, from top to bottom, of an upper gravel layer, a middle pyrite layer, a lower layer of a bacterial carbon composite filler containing zero-valent iron, and a bottom support layer of gravel. Gravel with a particle size of 5 to 10 mm was selected as the upper filler and bottom support layer.

[0103] The layer heights of the upper gravel layer, the middle pyrite layer, the lower carbon composite filler layer containing zero-valent iron, and the bottom supporting gravel layer account for 20%, 25%, 40% and 15% respectively.

[0104] The artificial wetland device also includes a water inlet pump, a water inlet pipe, a water inlet solenoid valve and an upper water outlet pipe, wherein the water inlet pipe is arranged in the bottom supporting layer gravel layer, and the water outlet pipe is arranged in the upper gravel layer.

[0105] The microbial electrochemical device is no longer required.

[0106] The artificial wetland device in this comparative example was subjected to application testing according to the implementation of Example 3.

[0107] Specific application examples

[0108] Example 3, Comparative Examples 1, 2 and 3 were specifically applied to the treatment of acid mine wastewater in a copper mining area in the central region, with an annual water treatment capacity of 500 to 800 tons. Before entering the device, the acid mine wastewater was first concentrated in the sedimentation tank in front of the water inlet. The hydraulic retention time of the device was set to 48 hours. After the device had been running stably for 20 days, it was monitored for 10 consecutive days to measure the concentration of pollutants in the wastewater and the effect of each system on pollutant reduction. The average value of the measurement results was taken. Among them, the pH of the untreated acid mine wastewater in the copper mining area was 2.34 to -2.75, and the main metal elements were Fe, Cu, Mn and Pb, with contents of 305.67 to 321.74 mg / L, 27.74 to 32.09 mg / L, 7.41 to 8.55 mg / L and 1.73 to 2.51 mg / L, respectively. The COD content was 36.75 to 51.52 mg / L, SO4 2- The content is 3596.44~3842.52 mg / L, posing a risk of environmental pollution.

[0109] Depend on Figure 4 It can be seen that the pH of the effluent treated in Example 3 increased by an average of 4.06 units compared to the untreated wastewater, while that of Comparative Examples 1, 2, and 3 increased by 3.11, 1.98, and 1.38 units, respectively. This indicates that Example 3 has a better effect than the comparative examples in alleviating the pH of AMD.

[0110] Wastewater enters each system from the water inlet for treatment. The removal effect of Fe, Cu, Mn and Pb in wastewater in Example 3 is significantly better than that of each comparative example ( Figure 4 ). In Example 3, the average removal rates for Fe, Cu, Mn, and Pb reached 94.88%, 94.53%, 93.34%, and 94.46%, respectively, with average concentrations in the effluent being 16.08 mg / L, 1.60 mg / L, 0.53 mg / L, and 0.12 mg / L, respectively. The total Pb concentration in the treated effluent was lower than the limit for the first category of pollutants in the Integrated Sewage Discharge Standard (GB 8978-1996), the Mn concentration met the first-level emission standard for the second category of pollutants in the standard, and the total Cu concentration met the third-level emission standard.

[0111] like Figure 5As shown, Example 3 performed better than the comparative examples in removing COD from the wastewater after it entered each system. After the system stabilized, the average COD removal rate in the effluent from Example 3 reached 96.15%, with an average concentration of 1.78 mg / L in the effluent, far below the emission limit specified in the Integrated Wastewater Discharge Standard (GB 8978-1996).

[0112] like Figure 6 As shown, wastewater enters each system for treatment. Compared with the comparative examples, Example 3 has a more significant reduction effect on sulfate in the wastewater. The average sulfate removal rate in the effluent of Example 3 reaches 94.88%, and the average concentration in the effluent is 189.98 mg / L.

[0113] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a bacterial carbon composite filler, characterized in that: The following steps are involved: (1) Acidic mine drainage sludge and Solidago canadensis stem powder were mixed and co-pyrolyzed to obtain biochar containing zero-valent iron; (2) After sterilizing the culture medium, add the diluted acid mine wastewater sludge solution and culture at a constant temperature under anaerobic conditions until the liquid turns black and has a rotten egg smell, thereby enriching the sulfate-reducing bacteria liquid; (3) adding the biochar material containing zero-valent iron in step (1) to the biological fermentation liquid, mixing, sterilizing and cooling to room temperature, adding the sulfate-reducing bacteria liquid in step (2) and performing constant temperature adsorption and fixation, sieving, rinsing, and obtaining a biochar composite filler containing zero-valent iron.

2. The method for preparing a bacterial carbon composite filler according to claim 1, characterized in that: The weight ratio of the acid mine wastewater sludge and the Solidago canadensis stem powder in step (1) is 2 to 3:1; And / or, the co-pyrolysis temperature in step (1) is 800-900° C. and the time is 2-4 h; and / or, the co-pyrolysis in step (1) is carried out in an inert gas atmosphere, wherein the inert gas is at least one of nitrogen, argon and helium; And / or, the biological fermentation liquid in step (3) is prepared by mixing biogas slurry produced by fermentation of rice straw and pig manure as farming waste with water, and has a pH of 7.11-7.52 and a COD content of 8324-10268 mg / L; And / or, in step (3), the ratio of the mass of the biochar material containing zero-valent iron, the volume of the biological fermentation liquid, and the volume of the sulfate-reducing bacteria liquid is 10-20 g: 100-250 mL: 5-10 mL; And / or, the constant temperature in step (3) is 30-35°C; And / or, the constant temperature adsorption fixation time in step (3) is 8 to 12 hours.

3. The method for preparing a bacterial carbon composite filler according to claim 1 or 2, characterized in that: The culture medium in step (2) is prepared by mixing K2HPO4, MgSO4·7H2O, Na2SO4, CaCl2·2H2O, yeast extract, DL-Na-lactate, (NH4)2SO4, vitamin B complex and trace element solution in a concentration ratio of 0.60.5-1g / L: 1.81.5-2.5g / L: 1.21-1.5g / L: 2.22-2.5g / L: 1.51-2g / L: 2.52-3g / L: 0.50.4-0.6g / L: 0.050.03-0.07g / L: 10.5-1.5mL / L; The yeast extract was LP0021B produced by Oxoid; the DL-Na-lactate was S817880 produced by Maclean; the vitamin B complex was prepared by mixing vitamins B1, B2, B3, B5, B6, B9 and B12 in proportions of 80-120 mg / g, 80-120 mg / g, 80-120 mg / g, 80-120 mg / g, 15-30 mg / g and 0.5-2 mg / g; the trace element solution contained Fe 2+ 、Mn 2+ 、Zn 2+ 、Co 2+ The concentrations were 1.5-3 mg / L, 0.3-0.7 mg / L, 0.05-2 mg / L and 0.05-0.2 mg / L respectively; And / or, the acid mine wastewater sludge dilution solution in step (2) is obtained by mixing acid mine wastewater sludge and water in a mass ratio of 1-2:4-10; and / or, the volume ratio of the culture medium to the acid mine wastewater sludge dilution in step (2) is 20-40:5-10; And / or, the constant temperature culture in step (2) is 30-35° C. and the time is 6-7 days.

4. A bacterial carbon composite filler prepared by the preparation method according to any one of claims 1 to 3.

5. Use of the bacterial carbon composite filler according to claim 4 in treating acidic mine wastewater.

6. A constructed wetland-microorganism electrochemical coupling system for treating AMD, characterized in that: It consists of two parts: artificial wetland device and microbial electrochemical device; The artificial wetland device includes a matrix and wetland plants located on the surface of the matrix, wherein the matrix is ​​composed of an upper gravel layer, a middle pyrite layer, a lower layer of the bacterial carbon composite filler containing zero-valent iron as claimed in claim 4, and a bottom supporting gravel layer from top to bottom; The microbial electrochemical device comprises an air cathode, a cathode, an anode and a solar power supply device; The air cathode is located on the surface of the artificial wetland matrix and is in contact with the air; The cathode is located in the middle layer of pyrite in the artificial wetland matrix; The anode is located in the lower layer of the artificial wetland matrix in the bacterial carbon composite filler containing zero-valent iron; One end of the anode is connected to the air cathode, and the other end is connected to the solar power supply device and the cathode in sequence.

7. The artificial wetland-microorganism electrochemical coupling system for treating AMD according to claim 6, characterized in that: The upper gravel layer, the middle pyrite layer, the lower layer of the bacterial carbon composite filler layer containing zero-valent iron according to claim 4, and the bottom supporting gravel layer have a layer height ratio of 15-25%, 20-30%, 30-50% and 10-15% respectively; And / or, the solar power supply device is located outside the artificial wetland device; And / or, the microbial electrochemical device further comprises a first external resistor and a second external resistor; the first external resistor is arranged between the anode and the air cathode, and the second external resistor is arranged between the solar power supply device and the cathode; And / or, the artificial wetland device further includes an inlet pipe and an outlet pipe; the inlet pipe is arranged in the bottom supporting gravel layer, and the outlet pipe is arranged in the upper gravel layer.

8. The artificial wetland-microorganism electrochemical coupling system for treating AMD according to claim 6 or 7, characterized in that: The particle size of the gravel is 5 to 10 mm; And / or, the wetland plant located on the surface of the substrate is at least one of sedge, water plantain, calamus, canna and reed; and / or, the connections are all made via insulated copper wires; And / or, the air cathode, cathode, and anode are all composed of graphite particles wrapped in a stainless steel mesh; the stainless steel mesh is 5-10 mesh; the particle size of the graphite particles is 1-2.5 mm; And / or, the solar power supply device includes a solar photovoltaic panel, a battery and a voltage conversion module.

9. A method for treating acid mine drainage based on the artificial wetland-microorganism electrochemical coupling system according to any one of claims 6 to 8, characterized in that: The following steps are involved: After removing floating and suspended solids from the acid mine drainage, it enters the artificial wetland-microbial electrochemical coupling system through the inlet pipe and undergoes retention treatment before being discharged through the outlet pipe.

10. The processing method according to claim 9, characterized in that: The residence time of the acid mine wastewater in the artificial wetland-microorganism electrochemical coupling system is 18 to 48 hours.

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