Magnetic coagulation-membrane separation combined treatment system and method suitable for mine wastewater

Abstract

This invention relates to the field of wastewater treatment technology, specifically to a magnetic coagulation-membrane separation combined treatment system and method suitable for mine wastewater. The system includes: magnetic coagulation reaction, where pollutants combine with magnetic seeds to form magnetic flocs; magnetically enhanced sedimentation, where pollutants settle rapidly under the influence of a permanent magnet-assisted magnetic field; recovery and recycling of magnetic seeds in the sludge hopper of the sedimentation tank; formation of a loose, porous filter cake layer on the membrane surface from residual magnetic seeds in an alternating magnetic field; enhanced magnetic field and supplemented with backwashing for magnetically enhanced online cleaning when the transmembrane pressure difference or membrane flux reaches a threshold; and intelligent linkage control of the entire process via online sensors and a PLC controller (S6). This invention integrates magnetic seed recovery within the sedimentation unit, achieving a magnetic seed recovery rate of over 95%; utilizes an alternating magnetic field to form a loose filter cake layer on the membrane surface from residual magnetic seeds and assists in cleaning, resulting in a high membrane flux recovery rate and extending the chemical cleaning cycle, thus achieving synergistic promotion of magnetic seed recovery and membrane fouling control.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a magnetic coagulation-membrane separation combined treatment system and method suitable for mine wastewater. Background Technology

[0002] Mine wastewater is the main industrial wastewater generated during mining and mineral processing. It is characterized by high suspended solids concentration, high turbidity, and the presence of heavy metal ions and small amounts of organic matter. Direct discharge without treatment will cause serious pollution to surrounding water bodies and the ecological environment. With increasingly stringent environmental standards and the worsening water shortage problem, the advanced treatment and reuse of mine wastewater has become an urgent need in the mining industry.

[0003] The magnetic coagulation-membrane separation combined process is a rapidly developing advanced wastewater treatment technology in recent years. Its basic principle is as follows: first, magnetic coagulation converts suspended solids, colloids, and some dissolved pollutants in the wastewater into magnetic flocs that settle rapidly; then, a membrane separation unit performs fine filtration to obtain high-quality reclaimed water. This combined process combines the advantages of high efficiency and small footprint of magnetic coagulation with the high quality of membrane-separated effluent, and has broad application prospects in fields such as mining wastewater, dyeing and printing wastewater, and electroplating wastewater.

[0004] However, existing magnetic coagulation-membrane separation combined systems have the following prominent problems in practical engineering applications:

[0005] 1. In existing magnetic coagulation processes, the magnetic seed, typically Fe3O4, settles with the magnetic flocs. The magnetic sludge at the bottom of the sedimentation tank needs to be transported to a separate magnetic seed recovery unit for processing. The conventional magnetic seed recovery process involves: the magnetic sludge is first strongly dispersed by a high-speed disperser, then the magnetic seed is separated from the sludge by a magnetic drum separator. The recovered magnetic seed is returned to the magnetic coagulation reactor for recycling. This process involves numerous devices and a long timeframe, resulting in significant seed loss during transport and dispersion. The conventional process achieves a seed recovery rate of only about 85%. This seed loss not only increases operating costs but also leads to seed accumulation in subsequent membrane separation units, exacerbating membrane fouling.

[0006] 2. Membrane fouling is a key bottleneck restricting the large-scale engineering application of membrane separation technology. In magnetic coagulation-membrane separation combined systems, although magnetic coagulation pretreatment can remove most suspended solids, a small amount of contaminants still enters the membrane system. Residual magnetic seeds in traditional systems are often considered a detrimental factor because they can enter the membrane system and cause membrane pore blockage or membrane surface abrasion. Membrane flux typically drops significantly after 1-2 hours of operation, requiring frequent backwashing. Chemical cleaning is generally needed every 1-2 weeks, and in severe cases, membrane modules may need to be replaced, resulting in high operating and maintenance costs.

[0007] 3. In existing technologies, magnetic seed recovery and membrane fouling control are two independent technical steps, completed by different equipment and processes. This not only increases system complexity and floor space but also fails to utilize the potential synergistic effects between the two. Traditional magnetic coagulation-membrane separation systems have dispersed units, requiring multiple maintenance and operation personnel, and the system lacks sufficient adaptive adjustment capability to water quality fluctuations.

[0008] To address the aforementioned issues, some improvements have been attempted. For example, Chinese patent CN103819045A discloses a wastewater reuse method combining magnetic loading coagulation and clarification with membrane separation, but its magnetic seed recovery still employs the traditional two-stage process of "high-speed disperser + magnetic drum separator." Chinese patent CN207845422U discloses a magnetic-membrane coupled reaction device that utilizes magnetic materials to delay membrane fouling, but its magnetic materials are fixed inside the membrane bioreactor, making online recovery and recycling of magnetic seeds impossible. Chinese patent CN218796508U discloses a magnetic seed deflocculation and recovery device that integrates deflocculation and magnetic seed recovery functions, but this device remains an independent recovery unit and does not synergize with the membrane separation unit.

[0009] Therefore, there is an urgent need in this field for a magnetic coagulation-membrane separation combined system and method that can simultaneously solve the two major problems of low magnetic seed recovery rate and severe membrane fouling, and achieve synergistic control of the two. Summary of the Invention

[0010] This invention aims to provide a magnetic coagulation-membrane separation combined treatment system and method suitable for mine wastewater, in order to solve the technical defects of existing magnetic coagulation-membrane separation combined systems, such as low magnetic seed recovery rate, serious membrane fouling, and lack of synergy between the two technical links; and to achieve the goals of improving magnetic seed recovery rate, reducing operating costs, effectively controlling membrane fouling, and extending the service life of membrane modules and chemical cleaning cycle.

[0011] To address the aforementioned technical problems, a first aspect of the present invention provides a magnetic coagulation-membrane separation combined treatment method suitable for mine wastewater, comprising the following specific steps:

[0012] S1. The wastewater is introduced into the magnetic coagulation reaction tank for magnetic coagulation reaction. Coagulant, coagulant aid and magnetic seed are added to the tank. Under the action of stirring, the suspended solids, colloids and dissolved pollutants in the wastewater combine with the magnetic seed to form magnetic flocs.

[0013] S2. The wastewater containing magnetic flocs is introduced into the inclined tube sedimentation tank for magnetically enhanced sedimentation. Under the action of the auxiliary magnetic field generated by the permanent magnet at the bottom of the tank, the magnetic flocs quickly settle into the sludge hopper at the bottom of the tank, and the supernatant enters the intermediate water tank.

[0014] S3. In-situ recovery of magnetic seeds is carried out in the sludge hopper of the inclined tube sedimentation tank.

[0015] Step S3 also includes the following steps:

[0016] S31. Compressed air is introduced into the sludge hopper to loosen and break up the magnetic flocs using the shearing force of the air bubbles.

[0017] S32. Apply ultrasonic waves to separate the magnetic seeds from the flocs;

[0018] S33. The crushed mud-water mixture passes through a magnetic roller separation device, where magnetic seeds are adsorbed onto the surface of the magnetic roller, and non-magnetic sludge is discharged with the water flow.

[0019] S34. The recovered magnetic seeds are returned to the magnetic coagulation reaction tank for recycling after being replenished with water and prepared.

[0020] S4. The supernatant in the intermediate water tank is introduced into the tubular membrane module for filtration. During the membrane separation process, the alternating electromagnetic field generator is turned on to generate an alternating magnetic field, which magnetizes the residual magnetic seeds in the supernatant and forms a loose and porous filter cake layer on the membrane surface.

[0021] S5. When the transmembrane pressure difference reaches the preset threshold or the membrane flux drops to the preset threshold, the inlet water is shut off, the magnetic field strength of the alternating electromagnetic field generator is increased, so that the magnetic seeds in the filter cake layer move towards the magnetic pole under the action of the magnetic field and drive the attached pollutants to detach from the membrane surface. At the same time, the reverse flushing is started to discharge the detached pollutants from the system.

[0022] S6. Water quality and operating parameters are collected in real time by online sensors, and the PLC controller automatically adjusts the magnetic seed dosage, membrane flux and cleaning program based on the collected data.

[0023] Preferably, the coagulant is polyaluminum chloride or polyferric sulfate, the coagulant aid is polyacrylamide, and the magnetic seed is iron(III) oxide with a particle size of 500 mesh.

[0024] Preferably, the magnetic field strength of the auxiliary magnetic field is 0.3-0.5T, and the hydraulic residence time is 4-6 minutes.

[0025] Preferably, the compressed air pressure is 0.3-0.5 MPa and the ultrasonic frequency is 20-40 kHz.

[0026] Preferably, in step S4, the magnetic field strength of the alternating magnetic field is 0.1-0.2T, the frequency is 50Hz, and the filtration method of the tubular membrane module is dead-end filtration or cross-flow filtration.

[0027] Preferably, in step S5, the magnetic field strength of the alternating electromagnetic field generator is increased to 0.3-0.5T during cleaning; the preset threshold for transmembrane pressure difference is 1.5 times the initial transmembrane pressure difference, and the preset threshold for membrane flux is 70% of the initial membrane flux.

[0028] A second aspect of the present invention provides a magnetic coagulation-membrane separation combined treatment system for mine wastewater, which uses the above-described method for treatment and includes a magnetic coagulation reaction unit, a magnetic seed enhanced precipitation unit, a magnetic seed in-situ recovery unit, a membrane separation unit, and an intelligent control unit connected in sequence.

[0029] The magnetic seed in-situ recovery unit is located inside the sludge hopper of the magnetic seed enhanced sedimentation unit and includes an air flushing device, an ultrasonic generator and a magnetic roller separation device.

[0030] The membrane separation unit includes a tubular membrane module and an alternating electromagnetic field generator disposed outside the tubular membrane module;

[0031] The intelligent control unit includes an online water quality monitoring sensor, a data acquisition module, and a PLC controller. The PLC controller is electrically connected to the dosing device of the magnetic coagulation reaction unit, each device of the magnetic seed in-situ recovery unit, the inlet pump and backwash pump of the membrane separation unit, and the alternating electromagnetic field generator.

[0032] Preferably, the magnetic seed enhancement sedimentation unit is an inclined tube sedimentation tank, with a bottom-mounted permanent magnet at the bottom to generate an auxiliary magnetic field to accelerate the sedimentation of magnetic flocs.

[0033] Preferably, the air flushing device includes an annular air distribution pipe disposed at the bottom of the sludge hopper and a compressed air source connected to the annular air distribution pipe;

[0034] The magnetic roller separation device includes a rotatable magnetic roller and a scraper plate disposed on the surface of the magnetic roller; a magnetic seed collection trough is provided at one end of the magnetic roller; the scraper plate guides the magnetic seed into the collection trough.

[0035] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0036] A fourth aspect of the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program: when the processor executes the computer program, it implements the steps of the above-described magnetic coagulation-membrane separation combined treatment system and method for mine wastewater.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. This invention integrates magnetic seed recovery into the sludge hopper of an inclined tube sedimentation tank. Utilizing air rinsing, ultrasonic crushing, and magnetic roller separation technologies, the entire process of magnetic sludge deflocculation, magnetic seed stripping, and magnetic seed recovery is completed in situ within the sedimentation unit. Compared to traditional two-stage recovery processes, this eliminates the magnetic seed sludge transportation stage, significantly reducing mechanical losses during transfer and crushing. While the magnetic seed recovery rate of ultra-magnetic separation water treatment processes typically reaches over 98%, this invention, through in-situ recovery and intelligent control, can stably maintain a magnetic seed recovery rate above 95%, significantly reducing the amount of magnetic seed replenishment and overall operating costs.

[0039] 2. This invention introduces an alternating magnetic field into the membrane separation unit, achieving dual anti-fouling functions: During operation, residual magnetic seeds are magnetized under the influence of the magnetic field and form a loose, porous filter cake layer on the membrane surface, which has higher permeability than the traditional dense filter cake layer, effectively delaying membrane flux decay; during cleaning, the enhanced magnetic field causes the magnetic seeds to actively remove pollutants from the membrane surface, achieving effective removal of irreversible fouling. After magnetically enhanced cleaning, the membrane flux recovery rate can reach over 97%, the chemical cleaning cycle can be significantly extended from the traditional 1-2 weeks to 1-2 months, and the service life of the membrane module can be extended by more than 50%.

[0040] 3. This invention ingeniously transforms the problem of residual magnetic seeds, which exacerbates membrane fouling in traditional systems, into a beneficial factor for proactive antifouling. Under the influence of an alternating magnetic field, the residual magnetic seeds become a key material for constructing a loose filter cake layer, while simultaneously acting as a cleaner during washing to actively remove contaminants. The magnetic seeds form a complete cycle in the system—coagulation—sedimentation—recovery—antifouling—regeneration—achieving the integrated goal of using magnets to control fouling, prevent fouling, and circulate magnetic seeds.

[0041] 4. This invention integrates the magnetic seed recovery unit into the sedimentation unit and the magnetically enhanced cleaning function into the membrane separation unit, resulting in a compact system structure and small footprint. Combined with the intelligent control unit's multi-parameter online monitoring and automatic control, it enables fully automated, unattended operation, significantly reducing labor costs and operational complexity. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort. In the drawings:

[0043] Figure 1 This is a flowchart of a magnetic coagulation-membrane separation combined treatment method for mine wastewater according to an embodiment of the present invention.

[0044] Figure 2This is a system diagram of a magnetic coagulation-membrane separation combined treatment system for mine wastewater according to an embodiment of the present invention. Detailed Implementation

[0045] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0046] As stated in the background section above, the present invention aims to optimize the technical defects of the existing magnetic coagulation-membrane separation combined system, such as low magnetic seed recovery rate, serious membrane fouling, and the lack of synergy between the two technical links.

[0047] Example 1

[0048] This embodiment proposes a magnetic coagulation-membrane separation combined treatment method suitable for mine wastewater, including the following specific steps:

[0049] S1, magnetic coagulation reaction

[0050] First, the mine wastewater is introduced into a magnetic coagulation reaction tank. Coagulants, flocculants, and magnetic seeds are added to the tank. Under the action of stirring, the suspended solids, colloids, and dissolved pollutants in the wastewater combine with the magnetic seeds to form magnetic flocs with the magnetic seeds as the core.

[0051] Mine wastewater contains a large amount of suspended solids, such as coal dust, mineral dust, colloidal particles, and a small amount of dissolved organic matter. Common coagulants include polyaluminum chloride or polyferric sulfate, which destabilize and aggregate small particles through charge neutralization and adsorption bridging. Coagulant aids such as polyacrylamide connect fine flocs into larger flocs through the bridging effect of long molecular chains. Magnetic seed iron oxide powder acts as the core of the flocs, giving the generated flocs magnetism and significantly increasing their density. The three work synergistically to form dense, magnetic flocs with excellent settling properties.

[0052] S2, magnetically enhanced precipitation

[0053] Wastewater containing magnetic flocs is introduced into an inclined tube sedimentation tank for magnetically enhanced sedimentation. Under the action of the auxiliary magnetic field generated by the permanent magnet at the bottom of the tank, the magnetic flocs quickly settle into the sludge hopper at the bottom of the tank, and the supernatant enters the intermediate water tank.

[0054] The inclined tube sedimentation tank is equipped with inclined tube packing material, which effectively improves sedimentation efficiency. A bottom-mounted permanent magnet at the bottom of the tank generates an auxiliary magnetic field with a strength of 0.3-0.5T, applying additional magnetic force to the magnetic flocs, accelerating their settling under the combined effects of gravity and magnetism. Compared to traditional coagulation sedimentation, the settling speed of magnetic flocs can be increased several times. The hydraulic retention time can be shortened to 4-6 minutes, significantly reducing the footprint of the sedimentation tank. After settling, the magnetic flocs enter the sludge hopper at the bottom of the tank, while the supernatant, having removed most suspended solids and colloids, flows through the supernatant effluent pipe into the intermediate tank, ready for subsequent membrane separation treatment.

[0055] S3, In-situ recovery of magnetic seeds

[0056] In the sludge hopper of the inclined tube sedimentation tank, magnetic seeds are recovered in situ. This step specifically includes the following sub-steps:

[0057] S31. Compressed air is introduced into the sludge hopper, and the shearing force of the air bubbles is used to loosen and break up the magnetic flocs. The compressed air is evenly distributed through an annular air distribution pipe at the bottom of the sludge hopper. As the air bubbles rise, they exert a shearing and impacting effect on the magnetic flocs, causing the dense magnetic flocs to initially loosen.

[0058] S32. Apply ultrasound to separate the magnetic seeds from the flocs. Ultrasound generates cavitation in the liquid, creating localized high temperature and pressure and strong microjets, which can effectively destroy the binding force between the magnetic seeds and pollutants in the flocs, thus completely separating the magnetic seeds from the flocs.

[0059] S33. The crushed mud-water mixture passes through a magnetic roller separator. Magnetic seeds are adsorbed onto the surface of the magnetic roller, while non-magnetic sludge is discharged with the water flow. The magnetic roller is a permanent magnet roller with a high magnetic field strength on its surface, which can effectively adsorb the stripped magnetic seed particles, while the sludge that has lost its magnetism is discharged from the sludge discharge port with the water flow.

[0060] S34. The recovered magnetic seeds are returned to the magnetic coagulation reactor for recycling after being replenished with water. The magnetic seeds adsorbed on the surface of the magnetic roller are scraped off by the scraper and placed into the magnetic seed collection tank. After being replenished with water to a suitable concentration, they are returned to the magnetic coagulation reactor through the magnetic seed addition device, thus realizing the recycling of magnetic seeds.

[0061] The above steps S31 to S34 are completed sequentially in the sludge hopper of the inclined tube sedimentation tank, realizing the integration of magnetic seed recovery and in-situ, eliminating the need to transport magnetic sludge to a separate magnetic seed recovery unit, greatly shortening the process flow and reducing the loss of magnetic seeds during the transfer process.

[0062] S4, magnetically reinforced membrane separation

[0063] The supernatant in the intermediate water tank is introduced into the tubular membrane module for filtration. During the membrane separation process, the alternating electromagnetic field generator is turned on to generate an alternating magnetic field, which magnetizes the residual magnetic seeds in the supernatant and forms a loose and porous filter cake layer on the membrane surface.

[0064] The supernatant after magnetic coagulation pretreatment still contains trace amounts of residual magnetic seeds with a particle size of micrometers and a small amount of unprecipitated fine contaminants. Under the action of an alternating magnetic field with a strength of 0.1-0.2T and a frequency of 50Hz, these residual magnetic seeds are magnetized. When the feed liquid containing magnetized magnetic seeds passes through the membrane surface, the magnetized magnetic seeds align in an orderly manner under the action of the magnetic field force, forming a filter cake layer on the membrane surface together with the fine contaminants. The magnetic field force and magnetic dipole force provided by the magnetic seeds can effectively increase the collision frequency and efficiency of colloidal particles in the water, increase the floc particle size and fractal dimension, and the filter cake layer formed by these flocs has a high porosity. This loose and porous filter cake layer has higher permeability than the traditional dense filter cake layer, which can effectively delay membrane flux decay.

[0065] Tubular membrane modules can use ultrafiltration membranes with a molecular weight cutoff of 50-150 kDa or microfiltration membranes with a pore size of 0.1-0.2 μm, and the filtration method can be dead-end filtration or cross-flow filtration.

[0066] S5, Magnetic Enhanced Online Cleaning

[0067] When the transmembrane pressure difference reaches the preset threshold or the membrane flux drops to the preset threshold, the inlet water is shut off, the magnetic field strength of the alternating electromagnetic field generator is increased, and the magnetic seeds in the filter cake layer move towards the magnetic pole under the action of the magnetic field and drive the attached pollutants to detach from the membrane surface. At the same time, the reverse flushing is started to discharge the detached pollutants from the system.

[0068] During membrane separation operation, the transmembrane pressure difference gradually increases as the filter cake layer thickens, while the membrane flux gradually decreases. When the transmembrane pressure difference reaches 1.5 times the initial value or the membrane flux drops to 70% of the initial value, the system automatically triggers the cleaning program. During cleaning, the magnetic field strength of the alternating electromagnetic field generator is increased to 0.3-0.5T. During the enhanced cleaning process with the external magnetic field, the magnetic seeds in the filter cake layer are magnetized, and the filter cake layer exhibits weak macroscopic magnetism, moving towards the magnetic poles under the influence of the magnetic field. The movement of the magnetic seeds carries the contaminants attached to them off the membrane surface. Simultaneously, backwashing is initiated, using reverse water flow to discharge the detached contaminants from the membrane module.

[0069] Compared to conventional physical cleaning, this magnetically enhanced online cleaning method can more effectively remove colloids and organic matter that cause irreversible membrane fouling, thus reducing the membrane fouling rate. After magnetically enhanced cleaning, the membrane flux recovery rate can reach over 97%.

[0070] S6, Intelligent Linkage Control

[0071] Water quality and operating parameters are collected in real time by online sensors, and the PLC controller automatically adjusts the magnetic seed dosage, membrane flux and cleaning program based on the collected data.

[0072] The system is equipped with multiple online sensors, including but not limited to: turbidity and suspended solids concentration sensors installed at the outlet of the magnetic coagulation reactor; magnetic seed concentration sensor installed at the outlet of the magnetic seed in-situ recovery unit; and membrane flux and transmembrane differential pressure sensors installed on the permeate pipe of the tubular membrane module. Each sensor collects data in real time and transmits it to the PLC controller.

[0073] The PLC controller automatically adjusts the dosage of coagulant and magnetic seed based on changes in influent water quality; it automatically determines whether a cleaning program needs to be started based on changes in membrane flux and transmembrane pressure difference, and controls the intensity and duration of cleaning; it automatically adjusts the supplementary dosage of magnetic seed based on the magnetic seed recovery rate, thereby achieving fully automatic and optimized operation of the system.

[0074] This invention utilizes the following steps: S1, magnetic coagulation reaction to combine pollutants with magnetic seeds to form magnetic flocs; S2, rapid sedimentation under the assistance of a permanent magnet to achieve solid-liquid separation; S3, in the sludge hopper of the sedimentation tank, a three-stage operation of compressed air loosening, ultrasonic stripping, and magnetic roller separation to recover magnetic seeds in situ and recycle them; S4, in an alternating magnetic field, converting residual magnetic seeds into beneficial components to construct a loose and porous filter cake layer to delay membrane fouling; S5, when the transmembrane pressure difference or membrane flux reaches a threshold, enhancing the magnetic field and supplementing it with reverse flushing to achieve magnetically enhanced online cleaning; and S6, through online sensors and a PLC controller, achieving intelligent linkage and control of the entire process. Each step is interconnected and works synergistically to achieve the integrated goal of efficient magnetic seed recovery and coordinated control of membrane fouling.

[0075] To further facilitate understanding of this solution, a specific case will be used for detailed explanation below:

[0076] The wastewater to be treated is mine water from a coal mine, with the following water quality parameters: suspended solids concentration 1200 mg / L, turbidity 680 NTU, COD 180 mg / L, and pH value 7.2.

[0077] S1, magnetic coagulation reaction

[0078] First, coal mine water is introduced into the magnetic coagulation reactor at a flow rate of 20 m³ / h. The stirring device is started, and the stirring speed is set to 150 rpm. Polyaluminum chloride is added to the reactor through the coagulant dosing pipe at a dosage of 100 mg / L, polyacrylamide is added through the coagulant aid dosing pipe at a dosage of 2 mg / L, and ferric oxide magnetic seeds (500 mesh particle size) are added through the magnetic seed dosing pipe at a dosage of 120 mg / L. The reaction is carried out for 5 minutes under stirring. Suspended solids, colloids, and some dissolved organic matter in the wastewater combine with the magnetic seeds to form dense magnetic flocs with the magnetic seeds as the core.

[0079] S2, magnetically enhanced precipitation

[0080] Wastewater containing magnetic flocs enters an inclined tube sedimentation tank. Under the influence of a 0.4T auxiliary magnetic field generated by a permanent magnet at the bottom of the tank, the magnetic flocs settle rapidly under the combined effects of gravity and magnetic force, with a hydraulic retention time of 5 minutes. The settled magnetic flocs enter the sludge hopper at the bottom of the tank, and the supernatant flows into the intermediate water tank through the supernatant outlet pipe. Multiple sampling and testing of the supernatant revealed that the average suspended solids concentration decreased to 35 mg / L, and the average turbidity decreased to 12 NTU.

[0081] S3, In-situ recovery of magnetic seeds

[0082] The following operations are performed sequentially in the sludge hopper of the inclined tube sedimentation tank:

[0083] S31. Compressed air is introduced into the sludge hopper through a compressed air source and annular air distribution pipe. The shearing force of the air bubbles is used to loosen and break up the magnetic flocs for 2 minutes.

[0084] S32. Start the ultrasonic generator and apply 30kHz ultrasonic waves to further separate the magnetic seeds from the flocs for 3 minutes.

[0085] S33. The crushed mud-water mixture passes through a magnetic roller separation device. The magnetic roller rotates at a speed of 60 rpm. During the rotation, the magnetic seeds are adsorbed onto the surface of the magnetic roller, and the non-magnetic sludge is discharged from the sludge discharge pipe with the water flow.

[0086] S34. The magnetic seeds adsorbed on the surface of the magnetic roller are scraped off by the scraper plate into the magnetic seed collection tank. The recovered magnetic seeds are then mixed with water and returned to the magnetic coagulation reaction tank for recycling through the magnetic seed dosing pipe. Testing showed that the magnetic seed recovery rate in this embodiment was 96.8%.

[0087] S4, magnetically reinforced membrane separation

[0088] The supernatant from the intermediate water tank is introduced into the tubular membrane module through the inlet pipe. The tubular membrane module uses an ultrafiltration membrane with a molecular weight cutoff of 100kDa for dead-end filtration, and the permeate flux is set at 50L / (m²·h). During membrane separation, an alternating electromagnetic field generator is activated to produce an alternating magnetic field of 0.15T and 50Hz. The trace magnetic seeds remaining in the supernatant are magnetized under the action of the magnetic field, forming a loose and porous filter cake layer on the membrane surface. Permeate water quality: suspended solids <1mg / L, turbidity <0.5NTU, COD <15mg / L, meeting the Class I standard requirements of the "Emission Standard of Pollutants for Coal Industry" (GB 20426-2006).

[0089] S5, Magnetic Enhanced Online Cleaning

[0090] After 8 hours of continuous operation, the transmembrane pressure difference increased from the initial 0.08 MPa to 0.12 MPa, reaching 1.5 times the initial threshold. The PLC controller automatically triggered the cleaning program: the inlet valve was closed, and the magnetic field strength of the alternating electromagnetic field generator was increased to 0.4T for 3 minutes, causing the magnetic seeds in the filter cake layer to move towards the magnetic poles under the influence of the magnetic field and carrying the attached contaminants off the membrane surface. Simultaneously, the backwash pump was turned on, and backwash water was introduced into the tubular membrane module through the backwash pipe at a backwash pressure of 0.04 MPa and a backwash flux of 80 L / (m²·h), discharging the detached contaminants from the system. After cleaning, the transmembrane pressure difference recovered to 0.085 MPa, and the membrane flux recovery rate was 97.5%. Actual engineering tests showed that using the scheme in this embodiment extended the chemical cleaning cycle from 2 weeks in the traditional process to 8 weeks.

[0091] Throughout the operation, turbidity sensors, suspended solids concentration sensors, magnetic seed concentration sensors, membrane flux sensors, and transmembrane pressure differential sensors collect data in real time and transmit it to the PLC controller. The PLC controller automatically adjusts the dosage of coagulant and magnetic seed based on changes in influent water quality; automatically determines whether a cleaning program needs to be initiated based on changes in membrane flux and transmembrane pressure differential; and automatically adjusts the magnetic seed replenishment dosage based on the magnetic seed recovery rate. The system achieves fully automatic operation without manual intervention.

[0092] Both the turbidity sensor and the suspended solids concentration sensor are located at the outlet of the magnetic coagulation reactor, specifically on the connecting pipe between the magnetic coagulation reactor and the inclined tube sedimentation tank. This location provides real-time feedback on the residual suspended solids and colloid content in the effluent after the magnetic coagulation reaction, serving as the most direct indicator for evaluating the effectiveness of magnetic coagulation.

[0093] Turbidity sensors and suspended solids concentration sensors monitor the turbidity and suspended solids concentration of the effluent from the magnetic coagulation reactor in real time and transmit the data to the PLC controller in real time.

[0094] The PLC controller performs the following control based on sensor feedback data:

[0095] 1. Coagulant dosage adjustment: When the turbidity or suspended solids concentration of the effluent increases, it indicates that the coagulant dosage is insufficient or the influent water quality is deteriorating. The PLC controller will automatically increase the coagulant dosage. When the effluent index is lower than the set value, the dosage will be appropriately reduced to save chemicals.

[0096] 2. Magnetic seed dosage adjustment: When the effluent turbidity and suspended solids concentration are consistently high and coagulant adjustment is ineffective, it indicates that the magnetic seed dosage may be insufficient. The PLC controller will automatically increase the magnetic seed dosage to enhance the flocculation effect.

[0097] 3. Stirring speed adjustment: The PLC controller can also adjust the speed of the stirring device in the magnetic coagulation reaction tank according to the feedback signal to optimize the coagulation reaction conditions.

[0098] Data from the turbidity sensor and the suspended solids concentration sensor can also serve as early warning signals for the subsequent membrane separation unit. When the effluent turbidity or suspended solids concentration exceeds the set threshold, the PLC controller will issue an early warning, indicating that the membrane separation unit may need to be monitored more closely or that cleaning should be prepared in advance.

[0099] The magnetic seed concentration sensor is installed at the outlet of the magnetic seed in-situ recovery unit, that is, on the outlet pipe of the magnetic seed collection tank in the magnetic roller separator. It is used to detect the concentration of the recovered magnetic seeds in real time, so as to calculate the magnetic seed recovery rate and determine the operating status of the magnetic seed recovery unit.

[0100] A magnetic seed concentration sensor monitors the concentration of the recovered magnetic seed in real time and transmits the data to the PLC controller. By comparing the amount of magnetic seed added with the concentration of the recovered magnetic seed, the PLC controller calculates the magnetic seed recovery rate in real time. When the recovery rate is lower than the set value, the system automatically adjusts the operating parameters of the in-situ magnetic seed recovery unit.

[0101] The amount of magnetic seed loss is calculated in real time based on the magnetic seed recovery rate, and the amount of magnetic seed replenishment is automatically adjusted. The lower the recovery rate, the greater the replenishment amount, ensuring that the magnetic seed concentration in the magnetic coagulation reactor remains stable.

[0102] When the magnetic seed concentration sensor detects that the concentration of the recovered magnetic seeds is abnormally low, the PLC controller automatically adjusts parameters such as compressed air pressure, ultrasonic frequency, or magnetic roller speed to optimize the magnetic seed recovery effect.

[0103] The data from the magnetic seed concentration sensor corroborate the data from the turbidity sensor and the suspended solids concentration sensor. If the magnetic seed recovery rate is normal but the effluent turbidity increases, the problem may lie in the coagulant addition process. If the magnetic seed recovery rate is low and the effluent turbidity increases, both the magnetic seed recovery and coagulant addition need to be adjusted simultaneously.

[0104] Both the membrane flux sensor and the transmembrane differential pressure sensor are installed on the permeate pipe of the tubular membrane module. The membrane flux sensor is used to monitor the permeate flow rate of the membrane module in real time; the transmembrane differential pressure sensor is used to monitor the pressure difference across the membrane in real time. The membrane flux sensor and the transmembrane differential pressure sensor monitor the operating status of the membrane module in real time and transmit the data to the PLC controller in real time.

[0105] Under constant permeate flux operation, the rate of increase in transmembrane pressure difference directly reflects the membrane fouling rate. The PLC controller monitors the changing trend of transmembrane pressure difference in real time and dynamically assesses the degree of membrane fouling.

[0106] When the transmembrane pressure difference reaches 1.5 times the initial value or the membrane flux drops to below 70% of the initial value, the PLC controller automatically triggers the magnetically enhanced online cleaning program.

[0107] After cleaning, the PLC controller compares the transmembrane pressure difference and membrane flux data before and after cleaning to evaluate the cleaning effect. If the membrane flux recovery rate is lower than the set value, the system automatically extends the cleaning time or increases the magnetic field strength.

[0108] The PLC controller predicts the optimal time for chemical cleaning based on the long-term trend of transmembrane pressure difference, avoiding waste caused by cleaning too early or irreversible membrane fouling caused by cleaning too late.

[0109] In constant transmembrane pressure differential operation mode, the PLC controller automatically adjusts the frequency of the feed pump based on the data from the membrane flux sensor to maintain a constant product water flux.

[0110] The data from the membrane flux sensor and the transmembrane differential pressure sensor, together with the data from the turbidity sensor and the suspended solids concentration sensor, form a feedforward-feedback linkage: when the turbidity sensor detects that the water quality of the magnetic coagulation effluent is deteriorating, the PLC controller can predict in advance that membrane fouling will accelerate and can proactively increase the frequency of magnetically enhanced cleaning or trigger the cleaning program in advance.

[0111] Example 2

[0112] The difference between this embodiment and Embodiment 1 is that the wastewater to be treated is a non-ferrous metal ore beneficiation wastewater with a suspended solids concentration of 850 mg / L, turbidity of 420 NTU, COD of 150 mg / L, and contains heavy metal ions such as lead and zinc. Polyferric sulfate is used as the coagulant, with a dosage of 80 mg / L, and the magnetic seed dosage is 100 mg / L. The bottom-mounted permanent magnet in the inclined tube sedimentation tank has a magnetic field strength of 0.5 T and a hydraulic retention time of 4 minutes. The tubular membrane module uses a microfiltration membrane with a pore size of 0.1 μm, and the alternating electromagnetic field generator operates with a magnetic field strength of 0.2 T. In the in-situ magnetic seed recovery unit, the air purging pressure is 0.35 MPa, and the ultrasonic frequency is 25 kHz.

[0113] Testing showed that after using the solution in this embodiment, the effluent suspended solids were <2 mg / L, turbidity was <0.8 NTU, COD was <20 mg / L, and heavy metal ion removal rate was >95%. The magnetic seed recovery rate was 95.8%, the membrane flux recovery rate was 96.8%, and the chemical cleaning cycle was extended from 1.5 weeks in the traditional process to 6 weeks.

[0114] Example 3

[0115] The difference between this embodiment and Embodiment 1 is that the tubular membrane module 51 adopts a cross-flow filtration method with a cross-flow velocity of 2 m / s. The operating magnetic field strength of the alternating electromagnetic field generator is 0.1 T. In the in-situ magnetic seed recovery unit, the ultrasonic frequency is 40 kHz. The compressed air pressure is 0.3 MPa.

[0116] Testing showed that after using the solution in this embodiment, the magnetic seed recovery rate was 95.2%, the membrane flux recovery rate was 97.8%, and the chemical cleaning cycle was extended from 2 weeks in the traditional process to 10 weeks. In the cross-flow filtration method, the membrane surface shear force is greater, and the filter cake layer thickness is thinner; combined with magnetically enhanced cleaning, a higher membrane flux recovery rate can be obtained.

[0117] Example 4

[0118] The difference between this embodiment and Embodiment 1 is that the wastewater to be treated is high-turbidity coal mine water, with a suspended solids concentration of 3500 mg / L and a turbidity of 1800 NTU. Polyaluminum chloride is used as the coagulant at a dosage of 150 mg / L, polyacrylamide as the coagulant aid at a dosage of 3 mg / L, and magnetic seed at a dosage of 180 mg / L. The magnetic coagulation reaction stirring time is 8 minutes. The hydraulic retention time for magnetically enhanced sedimentation is 6 minutes. In the in-situ recovery of the magnetic seed, the air purging pressure is 0.5 MPa, and the ultrasonic frequency is 20 kHz.

[0119] Testing showed that after using the solution in this embodiment, the effluent suspended solids were <5 mg / L, turbidity was <1.5 NTU, and COD was <25 mg / L. The magnetic seed recovery rate was 95.5%, the membrane flux recovery rate was 97.0%, and the chemical cleaning cycle was extended from 1 week in the traditional process to 5 weeks. This embodiment demonstrates that the present invention also has good treatment effect and operational stability for high-turbidity mine wastewater.

[0120] Example 5

[0121] like Figure 2 As shown, this embodiment provides a magnetic coagulation-membrane separation combined treatment system suitable for mine wastewater, which is treated using the methods in Examples 1-4. It includes a magnetic coagulation reaction unit, a magnetic seed enhanced sedimentation unit, a magnetic seed in-situ recovery unit, an intermediate water tank, a membrane separation unit, and an intelligent control unit connected in sequence.

[0122] The magnetic coagulation reaction unit includes a magnetic coagulation reaction tank, which is equipped with a stirring device. The top of the magnetic coagulation reaction tank is equipped with a coagulant dosing pipe, a coagulant aid dosing pipe, and a magnetic seed dosing pipe. The bottom of the magnetic coagulation reaction tank is connected to the inlet of an inclined tube sedimentation tank via a pipe.

[0123] The magnetic seed enhanced sedimentation unit includes an inclined tube sedimentation tank containing inclined tube packing material. The bottom of the sedimentation tank is a sludge hopper, the bottom of which is connected to the magnetic seed in-situ recovery unit. A bottom-mounted permanent magnet is installed on the outer side of the bottom of the inclined tube sedimentation tank to generate an auxiliary magnetic field of 0.3-0.5T. A supernatant effluent pipe is installed at the top of the sedimentation tank, connecting to an intermediate water tank.

[0124] The in-situ magnetic seed recovery unit is located inside the sludge hopper of the inclined tube sedimentation tank. The unit includes an air rinsing device, an ultrasonic generator, and a magnetic roller separator. The air rinsing device consists of an annular air distribution pipe at the bottom of the sludge hopper and a compressed air source connected to the pipe. Aeration holes at a 45° downward angle are staggered on both sides of the bottom of the annular air distribution pipe. The ultrasonic generator includes an ultrasonic generator and an ultrasonic transducer mounted on the inner wall of the sludge hopper, with an ultrasonic frequency of 20-40 kHz. The magnetic roller separator includes a rotatable magnetic roller and a scraper plate on the surface of the roller; a magnetic seed collection trough is located at one end of the roller. A sludge discharge pipe is also located at the bottom of the sludge hopper for discharging non-magnetic sludge.

[0125] The membrane separation unit includes a tubular membrane module and an alternating electromagnetic field generator located outside the tubular membrane module. The alternating electromagnetic field generator includes a coil surrounding the tubular membrane module, connected to an AC power supply, used to generate an alternating magnetic field. The magnetic field strength of the alternating electromagnetic field generator is adjustable, with an operating magnetic field strength of 0.1-0.2T and a cleaning magnetic field strength of 0.3-0.5T, at a frequency of 50Hz. The tubular membrane module is either an ultrafiltration membrane module or a microfiltration membrane module. One end of the tubular membrane module 51 is connected to an inlet pipe communicating with an intermediate water tank, and the other end is connected to a product water pipe, which is equipped with a product water valve. The tubular membrane module is also connected to a backwash pipe, which is equipped with a backwash pump and a backwash valve.

[0126] The intelligent control unit includes a PLC controller and online water quality monitoring sensors electrically connected to the PLC controller. The online water quality monitoring sensors include a turbidity sensor and a suspended solids concentration sensor installed at the outlet of the magnetic coagulation reactor, a magnetic seed concentration sensor installed at the outlet of the magnetic seed in-situ recovery unit, and a membrane flux sensor and a transmembrane differential pressure sensor installed on the permeate pipe of the tubular membrane module. The PLC controller is electrically connected to the power supply of the dosing pump, stirring device, compressed air source, ultrasonic generator, magnetic roller drive motor, tubular membrane module feed pump and backwash pump, and alternating electromagnetic field generator of the magnetic coagulation reactor.

[0127] This invention provides a system that can be widely applied to the deep treatment and resource reuse of various types of mine wastewater, such as coal mine water, non-ferrous metal ore dressing wastewater, and ferrous metal ore dressing wastewater. The system has a compact structure, a high degree of automation, and stable and reliable operation, demonstrating significant environmental and economic benefits, and possessing good industrial applicability and prospects for widespread application.

[0128] Example 6

[0129] According to one aspect of the present invention, a computer program product or computer program is provided, the computer program product or computer program including computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and executes the computer instructions, causing the computer device to perform the methods provided in the various alternative implementations described above.

[0130] In another aspect, the present invention also provides a computer-readable medium, which may be included in the electronic device described in the above embodiments; or it may exist independently and not assembled into the electronic device. The computer-readable medium carries one or more programs, which, when executed by the electronic device, cause the electronic device to implement the magnetic coagulation-membrane separation combined treatment system and method for mine wastewater as described in the above embodiments.

[0131] It should be noted that although several modules or units of the device for performing actions have been mentioned in the detailed description above, this division is not mandatory. In fact, according to embodiments of the present invention, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided and embodied by multiple modules or units.

[0132] Through the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein can be implemented by software or by combining software with necessary hardware. Therefore, the technical solutions according to the embodiments of the present invention can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (such as a CD-ROM, USB flash drive, portable hard drive, etc.) or on a network, including several instructions to cause a computing device (such as a personal computer, server, touch terminal, or network device, etc.) to execute the method according to the embodiments of the present invention.

[0133] Those skilled in the art will readily conceive of embodiments of the invention upon consideration of the specification and practice of the methods disclosed herein. The invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein.

[0134] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A magnetic coagulation-membrane separation combined treatment method suitable for mine wastewater, characterized in that, The specific steps include the following: S1. The wastewater is introduced into the magnetic coagulation reaction tank for magnetic coagulation reaction. Coagulant, coagulant aid and magnetic seed are added to the tank. Under the action of stirring, the suspended solids, colloids and dissolved pollutants in the wastewater combine with the magnetic seed to form magnetic flocs. S2. The wastewater containing magnetic flocs is introduced into the inclined tube sedimentation tank for magnetically enhanced sedimentation. Under the action of the auxiliary magnetic field generated by the permanent magnet at the bottom of the tank, the magnetic flocs quickly settle into the sludge hopper at the bottom of the tank, and the supernatant enters the intermediate water tank. S3. In-situ recovery of magnetic seeds is carried out in the sludge hopper of the inclined tube sedimentation tank. S4. The supernatant in the intermediate water tank is introduced into the tubular membrane module for filtration. During the membrane separation process, the alternating electromagnetic field generator is turned on to generate an alternating magnetic field, which magnetizes the residual magnetic seeds in the supernatant and forms a loose and porous filter cake layer on the membrane surface. S5. When the transmembrane pressure difference reaches the preset threshold or the membrane flux drops to the preset threshold, the inlet water is shut off, the magnetic field strength of the alternating electromagnetic field generator is increased, so that the magnetic seeds in the filter cake layer move towards the magnetic pole under the action of the magnetic field and drive the attached pollutants to detach from the membrane surface. At the same time, the reverse flushing is started to discharge the detached pollutants from the system. S6. Water quality and operating parameters are collected in real time by online sensors, and the PLC controller automatically adjusts the magnetic seed dosage, membrane flux and cleaning program based on the collected data.

2. The magnetic coagulation-membrane separation combined treatment method for mine wastewater according to claim 1, characterized in that, The coagulant is polyaluminum chloride or polyferric sulfate, the coagulant aid is polyacrylamide, and the magnetic seed is iron(III) oxide with a particle size of 500 mesh.

3. The magnetic coagulation-membrane separation combined treatment method for mine wastewater according to claim 1, characterized in that, The magnetic field strength of the auxiliary magnetic field is 0.3-0.5T, and the hydraulic residence time is 4-6 minutes.

4. The magnetic coagulation-membrane separation combined treatment method for mine wastewater according to claim 1, characterized in that, Step S3 also includes the following steps: S31. Compressed air is introduced into the sludge hopper to loosen and break up the magnetic flocs using the shearing force of the air bubbles. S32. Apply ultrasonic waves to separate the magnetic seeds from the flocs; S33. The crushed mud-water mixture passes through a magnetic roller separation device, where magnetic seeds are adsorbed onto the surface of the magnetic roller, and non-magnetic sludge is discharged with the water flow. S34. The recovered magnetic seeds are returned to the magnetic coagulation reactor for recycling after being replenished with water and prepared.

5. The magnetic coagulation-membrane separation combined treatment method for mine wastewater according to claim 4, characterized in that, The compressed air pressure is 0.3-0.5MPa, and the ultrasonic frequency is 20-40kHz.

6. The magnetic coagulation-membrane separation combined treatment method for mine wastewater according to claim 1, characterized in that, In step S4, the magnetic field strength of the alternating magnetic field is 0.1-0.2T, the frequency is 50Hz, and the filtration method of the tubular membrane module is dead-end filtration or cross-flow filtration.

7. The magnetic coagulation-membrane separation combined treatment method for mine wastewater according to claim 1, characterized in that, In step S5, the magnetic field strength of the alternating electromagnetic field generator is increased to 0.3-0.5T during cleaning; the preset threshold for transmembrane pressure difference is 1.5 times the initial transmembrane pressure difference, and the preset threshold for membrane flux is 70% of the initial membrane flux.

8. A magnetic coagulation-membrane separation combined treatment system for mine wastewater, wherein the method described in any one of claims 1-7 is used for treatment, characterized in that, It includes a magnetic coagulation reaction unit, a magnetic seed enhanced precipitation unit, a magnetic seed in-situ recovery unit, a membrane separation unit, and an intelligent control unit connected in sequence; The magnetic seed in-situ recovery unit is located inside the sludge hopper of the magnetic seed enhanced sedimentation unit and includes an air flushing device, an ultrasonic generator and a magnetic roller separation device. The membrane separation unit includes a tubular membrane module and an alternating electromagnetic field generator disposed outside the tubular membrane module; The intelligent control unit includes an online water quality monitoring sensor, a data acquisition module, and a PLC controller. The PLC controller is electrically connected to the dosing device of the magnetic coagulation reaction unit, each device of the magnetic seed in-situ recovery unit, the inlet pump and backwash pump of the membrane separation unit, and the alternating electromagnetic field generator.

9. The magnetic coagulation-membrane separation combined treatment system for mine wastewater according to claim 8, characterized in that, The magnetic seed enhancement sedimentation unit is an inclined tube sedimentation tank, with a bottom-mounted permanent magnet at the bottom to generate an auxiliary magnetic field to accelerate the sedimentation of magnetic flocs.

10. The magnetic coagulation-membrane separation combined treatment system for mine wastewater according to claim 8, characterized in that, The air flushing device includes an annular air distribution pipe located at the bottom of the sludge hopper and a compressed air source connected to the annular air distribution pipe. The magnetic roller separation device includes a rotatable magnetic roller and a scraper plate disposed on the surface of the magnetic roller; a magnetic seed collection trough is provided at one end of the magnetic roller; the scraper plate guides the magnetic seed into the collection trough.

Images