A heavy metal wastewater treatment system and method

Abstract

This invention discloses a heavy metal wastewater treatment system and method, belonging to the field of heavy metal wastewater treatment. The heavy metal wastewater treatment system includes, in sequence, a wastewater equalization tank, a pH equalization tank, a coagulation reaction device, a circulation tank, a microfiltration membrane system, a microfiltration permeate tank, and a membrane concentration system. The sludge outlet of the circulation tank is connected to a sludge tank, and the sludge outlet of the sludge tank is connected to a filter press. The membrane concentration system has a permeate outlet and a condensate outlet. The permeate outlet is connected to a discharge tank, and the condensate outlet returns to the microfiltration permeate tank. The heavy metal wastewater treatment system and method of this invention produce effluent that meets the Class III water discharge requirements of the "Surface Water Environmental Quality Standard" (GB3838-2002) and can yield crystalline salts.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal wastewater treatment, and particularly relates to a heavy metal wastewater treatment system and method. Background Technology

[0002] Heavy metal wastewater contains not only heavy metal ions such as lead, copper, nickel, and chromium, but also pollutants such as COD, ammonia nitrogen, and phosphorus. If these pollutants are not pretreated, they will affect the subsequent membrane.

[0003] Furthermore, existing heavy metal wastewater treatment methods cannot meet the Class III water discharge standards of the "Surface Water Environmental Quality Standard" (GB3838-2002). Summary of the Invention

[0004] The purpose of this invention is to provide a heavy metal wastewater treatment system and method to overcome at least one of the above-mentioned defects in the prior art.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] The present invention provides a heavy metal wastewater treatment system, comprising a wastewater equalization tank, a pH equalization tank, a coagulation reaction device, a circulation tank, a microfiltration membrane system, a microfiltration permeate tank, and a membrane concentration system connected in sequence. The sludge outlet of the circulation tank is connected to a sludge tank, and the sludge outlet of the sludge tank is connected to a filter press. The membrane concentration system has a permeate outlet and a condensate outlet. The permeate outlet is connected to a discharge tank, and the condensate outlet is returned to the microfiltration permeate tank.

[0007] Preferably, the coagulation reaction equipment includes a coagulation tank, a support frame, an inlet pipe, an outlet pipe, a stirrer, a slide rail, a first slider, an air supply component, a valve, and a connecting rod. The support frame is fixed to the top wall of the coagulation tank, the slide rail is fixed to the middle of the right side wall of the support frame, the first slider is slidably connected to the slide rail, the stirrer is fixed to the bottom of the slider, and the stirring end of the stirrer extends into the coagulation tank. The air supply component is fixed to the top wall of the support frame, the air supply end of the air supply component is located at the bottom of the coagulation tank and below the stirring end of the stirrer, the air supply component has a left and right moving end, the left and right moving end is fixedly connected to the first slider through the connecting rod, the inlet pipe is fixedly connected to the upper left side wall of the coagulation tank, and the outlet pipe is fixedly connected to the lower right side wall of the coagulation tank, and a valve is installed on the outlet pipe.

[0008] Preferably, the agitator includes a mounting plate, a mounting rod, a first motor, a sealing box, a first stirring shaft, a first stirring blade, a first bearing seat, a first bevel gear, a second bevel gear, a second bearing seat, a second stirring shaft, and a second stirring blade. The mounting plate is fixed to the bottom wall of the first slider, and the first motor and mounting rod are fixed to the bottom wall of the mounting plate. The sealing box is fixed to the bottom end of the mounting rod, and the first bearing seat is fixed to the center of the bottom wall of the sealing box. The first stirring shaft is fixed to the bottom end of the first motor, and the lower part of the first stirring shaft passes through the sealing box and the first bearing seat, extending into the interior of the coagulation tank for fixation. The bottom wall of the sealing box with several first stirring blades has upward sloping walls on both the left and right sides. The top of the sloping walls is fixed with a second bearing seat. The top of the second stirring shaft is fixed with a second bevel gear. The first bevel gear is located inside the sealing box and is fixed to the first stirring shaft. The second bevel gear meshes with the first bevel gear. The lower part of the second stirring shaft passes through the sealing box and extends into the interior of the coagulation tank where several second stirring blades are fixed. The first stirring shaft is set vertically. The first stirring shaft and the second stirring shaft are set at an angle. The first stirring blades are perpendicular to the first stirring shaft, and the second stirring blades are perpendicular to the second stirring shaft.

[0009] Preferably, the first stirring blade and the second stirring blade are staggered.

[0010] Preferably, the air supply assembly includes a second motor, a rotating shaft, a first swing arm, a second swing arm, a cylinder, a piston, an air inlet pipe, a first one-way valve, an air outlet pipe, a second one-way valve, and an air distribution component. The cylinder and the second motor are fixed to the inner top wall of the bracket. The rotating shaft is fixed to the front end of the second motor. One end of the first swing arm is fixed to the rotating shaft, and the other end of the first swing arm is hinged to the second swing arm. The piston is slidably connected inside the cylinder. The middle part of the right side wall of the piston is hinged to the second swing arm. The lower part of the right side wall of the piston is fixedly connected to the upper end of the connecting rod. The lower end of the connecting rod extends out of the cylinder and is fixedly connected to the first slider. The air inlet pipe is fixedly connected to the left side of the top wall of the cylinder. The first one-way valve is located in the air inlet pipe. The air outlet pipe is fixedly connected to the left side wall of the cylinder. The second one-way valve is located in the air outlet pipe. The bottom end of the air outlet pipe passes through the left side wall of the coagulation tank and extends into the interior of the coagulation tank, where the air distribution component is fixedly connected. The air distribution component is located below the stirring end of the agitator. The contact point between the air outlet pipe and the left side wall of the coagulation tank is sealed.

[0011] Preferably, the air distribution component includes a raised block, an outer ring, an inner ring, and connecting pipes. The raised block is fixed to the inner bottom wall of the coagulation tank, and the outer ring is fixed to the top of the raised block. The outer ring is connected to the air outlet pipe. Several connecting pipes are fixedly connected to the inner side wall of the outer ring. The inner end of the connecting pipe is fixedly connected to the inner ring. The outer ring surrounds the inner ring. Several first air distribution holes are opened at the top of the outer ring, and several second air distribution holes are opened at the top of the inner ring. The first air distribution holes are evenly spaced along the circumference of the outer ring, and the second air distribution holes are evenly spaced along the circumference of the inner ring.

[0012] Preferably, it also includes a fixed plate, an electric push rod, a second slider, a connecting rod, a vertical plate, a first automatic reset switch, a second automatic reset switch, a cam, a first dosing device, and a second dosing device. A fixed plate is fixed to the upper part of the inner wall of the support. A groove is formed on the top of the fixed plate, and two second sliders are slidably connected within the groove. The two second sliders are connected by a connecting rod. A vertical plate is fixed to the top wall of the second sliders. The first automatic reset switch is fixed to the left side wall of the right vertical plate, and the second automatic reset switch is fixed to the right side wall of the left vertical plate. A connection is fixed to the right side of the top wall of the coagulation tank. The first dosing device is fixedly connected to the left side of the top wall of the coagulation tank, and the second dosing device is electrically connected to the first and second automatic reset switches. An electric push rod is fixed to the top wall of the fixed plate, and the left end of the electric push rod is fixedly connected to the vertical plate located on the right side. The cam is fixed to the rotating shaft and located in front of the first swing arm. The second and first automatic reset switches are located on the left and right sides of the cam, respectively. The straight-line distance between the first and second automatic reset switches is D, and the straight-line distance from the axis of the rotating shaft to the distal end of the cam is d, where D > 2d.

[0013] Preferably, the membrane concentration system includes an NF system, an NF concentrate tank, an RO system, an RO concentrate tank, and an evaporator connected in sequence. The product water outlets of the NF system and the RO system are both connected to the discharge tank, and the condensate outlet of the evaporator is connected to the microfiltration product water tank.

[0014] This invention also provides a method for treating heavy metal wastewater, using the aforementioned heavy metal wastewater treatment system, comprising the following steps: Heavy metal wastewater is fed into a wastewater equalization tank to adjust water quality and quantity, then into a pH equalization tank. Sodium hydroxide is added to the pH equalization tank to adjust the wastewater to a pH of 8.0-9.0, causing some of the metal pollutants in the wastewater to form hydroxide precipitates. After the reaction is complete, the wastewater flows by gravity into a coagulation reaction device. A heavy metal precipitant and a flocculant are added sequentially to the coagulation reaction device, forming flocculated sediment that then enters a circulation tank. The sludge at the bottom of the circulation tank is discharged into a sludge tank and sent to a filter press for pressing. The sludge cake is outsourced for treatment. The wastewater from the circulation tank is sent to a microfiltration membrane system for filtration. The resulting permeate is sent to a microfiltration permeate tank, then into a membrane concentration system for concentration and evaporation to obtain crystalline salt. The permeate from the membrane concentration system is sent to a discharge tank and discharged after meeting standards. The condensate from the membrane concentration system is sent to the microfiltration permeate tank and, together with the permeate from the microfiltration membrane system, re-enters the membrane concentration system for treatment.

[0015] Preferably, the membrane concentration system includes an NF system, an NF concentrate tank, an RO system, an RO concentrate tank, and an evaporator connected in sequence. The effluent from the microfiltration permeate tank enters the NF system for nanofiltration treatment. The concentrate produced by nanofiltration enters the NF concentrate tank and then enters the RO system for reverse osmosis treatment. The concentrate produced by reverse osmosis enters the RO concentrate tank and serves as the raw water for the evaporator. The evaporator evaporates and crystallizes the water to obtain crystalline salt. The condensate produced by the evaporator is sent to the microfiltration permeate tank. The permeate produced by nanofiltration and reverse osmosis enters the discharge tank.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. The treated wastewater effluent meets the Class III water discharge requirements of the "Surface Water Environmental Quality Standard" (GB3838-2002) and can produce crystalline salt.

[0018] 2. While the agitator is agitating, the air supply component intermittently supplies air into the coagulation tank, generating bubbles. These bubbles act as agitators, further improving agitation efficiency. During intermittent air supply, the left-right moving end of the air supply component repeatedly moves left and right, driving the slider to do the same through the connecting rod. This causes the agitator to move repeatedly left and right, resulting in more comprehensive and efficient agitation, combined with the agitator's own stirring action.

[0019] 3. A single motor is sufficient to achieve the effect of the central first stirring blade rotating forward while the two left and right second stirring blades rotate in reverse. This combination of forward and reverse stirring directions greatly improves stirring efficiency. Furthermore, it requires only one motor, demonstrating ingenious design and cost-effectiveness.

[0020] 4. Because the first and second stirring shafts are set at an angle, stirring is carried out in both vertical and inclined directions, which greatly improves the stirring effect.

[0021] 5. Based on the combination of one positive and two negative stirring directions and stirring in both vertical and inclined positions, the first and second stirring blades are staggered to make the stirring more comprehensive.

[0022] 6. By distributing air from different positions through inner and outer rings, the air distribution effect is better and the mixing effect is better.

[0023] 7. By setting a second motor, it not only serves as the driving source for air supply, but also as the driving source for adjusting the left and right position of the agitator, and as the basis for intermittent chemical dosing. Multiple combinations achieve diversified functions, thereby improving the mixing and coagulation efficiency in different ways. Attached Figure Description

[0024] Figure 1 This is a system block diagram of the heavy metal wastewater treatment system of the present invention.

[0025] Figure 2 This is a schematic diagram of the main structure of the heavy metal wastewater treatment system of the present invention.

[0026] Figure 3 This is a schematic diagram of the main structure of the stirrer of the present invention.

[0027] Figure 4 This is a partial front view structural schematic diagram of the gas supply component of the present invention.

[0028] Figure 5 This is a top view of the air distribution component of the present invention.

[0029] Figure 6 This is a schematic diagram of the cooperative structure of the cam, the first automatic reset switch, and the second automatic reset switch of the present invention.

[0030] The labels in the attached diagram are as follows: 100-Wastewater equalization tank, 200-pH equalization tank, 300-Coagulation reaction equipment, 400-Circulation tank, 500-Microfiltration membrane system, 600-Microfiltration permeate tank, 800-Sludge tank, 900-Filter press, 1000-Discharge tank, 1100-NF system, 1200-NF concentrate tank, 1300-RO system, 1400-RO concentrate tank, 1500-Evaporator, 1-Coagulation tank, 2-Support, 3-Inlet pipe, 4-Discharge pipe, 5-Agitator, 6-Slide rail, 7-First slider, 8-Air supply assembly, 9-Valve, 10-Connecting rod, 51-Mounting plate, 52-Mounting rod, 53-First motor, 54-Sealing box, 55-First stirring shaft, 56-First stirring blade, 57-First bearing seat, 58-First bevel gear 59-Second bevel gear, 510-Second bearing seat, 511-Second stirring shaft, 512-Second stirring blade, 81-Second motor, 82-Rotating shaft, 83-First swing arm, 84-Second swing arm, 85-Cylinder body, 86-Piston, 87-Inlet pipe, 88-First one-way valve, 89-Outlet pipe, 810-Second one-way valve, 811-Air distribution component, 8111-Elevating block, 8112-Outer ring, 8113-Inner ring, 8114-Connecting pipe, 8115-First air distribution hole, 8116-Second air distribution hole, 11-Fixing plate, 12-Electric push rod, 13-Second slider, 14-Connecting rod, 15-Upright plate, 16-First automatic reset switch, 17-Second automatic reset switch, 18-Cam, 19-First dosing device, 20-Second dosing device, 21-Slide groove. Detailed Implementation

[0031] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0032] Contents not described in detail in this specification are prior art known to those skilled in the art. In the description of this invention, it should be understood that terms such as "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, terms such as "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] like Figures 1 to 6 As shown, the heavy metal wastewater treatment system provided in this embodiment includes a wastewater equalization tank 100, a pH equalization tank 200, a coagulation reaction device 300, a circulation tank 400, a microfiltration membrane system 500, a microfiltration permeate tank 600, and a membrane concentration system connected in sequence. The sludge outlet of the circulation tank 400 is connected to a sludge tank 800, and the sludge outlet of the sludge tank 800 is connected to a filter press 900. The membrane concentration system has a permeate outlet and a condensate outlet. The permeate outlet is connected to a discharge tank 1000, and the condensate outlet flows back to the microfiltration permeate tank 600.

[0034] This embodiment also provides a method for treating heavy metal wastewater, which uses the above-mentioned heavy metal wastewater treatment system and includes the following steps:

[0035] Heavy metal wastewater is collected and sent to wastewater equalization tank 100 via a collection network to adjust water quality and quantity. Then, a booster pump is used to pump the wastewater to pH equalization tank 200, where sodium hydroxide is added to adjust the pH to 8.0-9.0. This causes some of the metal pollutants in the wastewater to precipitate as hydroxides. After the reaction is complete, the wastewater flows by gravity into coagulation reactor 300. Heavy metal chelating agent and flocculant are added sequentially to coagulation reactor 300. The heavy metal chelating agent is a chemical agent that strongly chelates heavy metal ions, reacting chemically with various heavy metal ions in the wastewater to rapidly generate insoluble, low-water-content, easily filtered flocculent precipitates within a short time. The coagulant polyaluminum chloride causes the flocculent precipitates in the wastewater to form flocs with a specific gravity greater than water, which then enter the circulation tank 400. The sludge at the bottom of the circulation tank 400 is discharged into the sludge tank 800 and pumped into the filter press 900 for pressing. The sludge cake is then outsourced for treatment. The wastewater from the circulation tank 400 is sent to the ULTRAFLOW microfiltration membrane system 500 for filtration. The resulting permeate is sent to the microfiltration permeate tank 600 and then enters the membrane concentration system for concentration and evaporation to obtain crystalline salt. The permeate from the membrane concentration system is sent to the discharge tank 1000 and discharged after meeting the standards. The condensate from the membrane concentration system is sent to the microfiltration permeate tank 600 and, together with the permeate from the microfiltration membrane system 500, re-enters the membrane concentration system for treatment.

[0036] The wastewater treated by this invention must meet the Class III water discharge concentration limits of the "Surface Water Environmental Quality Standard" (GB3838-2002), which has high discharge requirements. To ensure that the effluent meets the discharge requirements, an NF system 1100 is installed at the front end of the membrane concentration system. The NF membrane can retain organic matter with a molecular weight greater than 100 and divalent ions, while allowing small organic molecules and monovalent ions to pass through. After the wastewater is concentrated by approximately 5.0 times by the NF membrane, the product water can enter the discharge tank 1000 for monitoring and discharge to meet the standards. The concentrated water from nanofiltration enters the NF concentrated water tank 1200. To reduce the investment and operating costs of the evaporator 1500, the concentrated liquid from the NF system 1100 enters the RO membrane concentration system for further concentration by 2 times, reducing the amount of water entering the evaporator 1500. With the concentration of water through the membrane, the salt content and pollutants will continuously increase. At this point, the wastewater concentration ratio before evaporation is approximately 10 times, and the salt content and pollutants will be amplified tenfold. The concentrated water from reverse osmosis enters the RO concentrated water tank 1400 as the raw water for the evaporator 1500, and then enters the scraped evaporator 1500 for evaporation. The resulting crystalline salt is outsourced for treatment. The condensate from the evaporator 1500 is sent to the microfiltration permeate tank 600, while the permeate from nanofiltration and reverse osmosis enters the discharge tank 1000. The wastewater treated in this way meets the Class III water discharge requirements of the "Surface Water Environmental Quality Standard" (GB3838-2002) and yields crystalline salt.

[0037] The coagulation reaction equipment 300 includes a coagulation tank 1, a support 2, an inlet pipe 3, an outlet pipe 4, a stirrer 5, a slide rail 6, a first slider 7, an air supply component 8, a valve 9, and a connecting rod 10. The support 2 is fixed to the top wall of the coagulation tank 1. The slide rail 6 is fixed to the middle of the right side wall inside the support 2. The first slider 7 is slidably connected to the slide rail 6. The stirrer 5 is fixed to the bottom of the slider, and the stirring end of the stirrer 5 extends into the coagulation tank 1. The air supply component 8 is fixed to the top wall inside the support 2. The air supply end of the air supply component 8 is located at the bottom of the coagulation tank 1 and below the stirring end of the stirrer 5. The air supply component 8 has left and right movable ends, which are fixedly connected to the first slider 7 via the connecting rod 10. The inlet pipe 3 is fixedly connected to the upper left side wall of the coagulation tank 1, and the outlet pipe 4 is fixedly connected to the lower right side wall of the coagulation tank 1. A valve 9 is installed on the outlet pipe 4. First, a heavy metal precipitant is added, and the stirrer 5 is used to accelerate the mixing efficiency between the heavy metal precipitant and the wastewater. Then, flocculant is added, and the agitator 5 accelerates the flocculation reaction, improving overall treatment efficiency. While the agitator 5 is agitating, the air supply component 8 intermittently supplies air to the coagulation tank 1, generating bubbles. These bubbles act as agitators, further enhancing agitation efficiency. During intermittent air supply, the left-right moving end of the air supply component 8 repeatedly moves left and right, driving the slider to move left and right repeatedly via the connecting rod 10. This causes the agitator 5 to move repeatedly left and right, resulting in more comprehensive and efficient agitation, combined with the agitator 5's own stirring action.

[0038] The agitator 5 includes a mounting plate 51, a mounting rod 52, a first motor 53, a sealing box 54, a first stirring shaft 55, a first stirring blade 56, a first bearing seat 57, a first bevel gear 58, a second bevel gear 59, a second bearing seat 510, a second stirring shaft 511, and a second stirring blade 512. The mounting plate 51 is fixed to the bottom wall of the first slider. The first motor 53 and the mounting rod 52 are fixed to the bottom wall of the mounting plate 51. The sealing box 54 is fixed to the bottom end of the mounting rod 52. The first bearing seat 57 is fixed to the center of the bottom wall of the sealing box 54. The first stirring shaft 55 is fixed to the bottom end of the first motor 53. The lower part of the first stirring shaft 55 passes through the sealing box 54 and the first bearing seat 57 and extends into the interior of the coagulation tank 1. The bottom wall of the sealed box 54, which is fixed with several first stirring blades 56, has upwardly sloping walls on both sides. A second bearing seat 510 is fixed to the top of the sloping walls. A second bevel gear 59 is fixed to the top of the second stirring shaft 511. A first bevel gear 58 is located inside the sealed box 54 and fixed to the first stirring shaft 55. The second bevel gear 59 meshes with the first bevel gear 58. The lower part of the second stirring shaft 511 passes through the sealed box 54 and extends into the interior of the coagulation tank 1, where several second stirring blades 512 are fixed. The first stirring shaft 55 is vertically arranged, and the first stirring shaft 55 and the second stirring shaft 511 are arranged at an angle. The first stirring blades 56 are perpendicular to the first stirring shaft 55, and the second stirring blades 512 are perpendicular to the second stirring shaft 511. The first motor 53 rotates, driving the first stirring shaft 55 to rotate, causing the first stirring blades 56 to perform stirring operations. The first stirring shaft 55 drives the first bevel gear 58 to rotate, which in turn causes the two second bevel gears 59 on the left and right to rotate, which in turn drives the second stirring shaft 511 to rotate, causing the second stirring blades 512 to rotate. Due to the meshing of the first bevel gears 58 and the second bevel gears 59, the stirring directions of the first stirring shaft 55 and the second stirring shaft 511 are opposite. A single first motor 53 can achieve the effect of the central first stirring blade 56 rotating clockwise, while the two left and right second stirring blades 512 rotate counterclockwise. This combination of one clockwise and two counterclockwise stirring directions greatly improves stirring efficiency. Furthermore, only one first motor is needed, demonstrating ingenious design and cost-effectiveness. Because the first stirring shaft 55 and the second stirring shaft 511 are angled, stirring is performed in both vertical and inclined directions, significantly enhancing the stirring effect.

[0039] The first stirring blade 56 and the second stirring blade 512 are staggered. Based on the combination of one positive and two negative stirring directions and stirring in both vertical and inclined positions, the staggered arrangement of the first stirring blade 56 and the second stirring blade 512 further makes the stirring more comprehensive.

[0040] The air supply assembly 8 includes a second motor 81, a rotating shaft 82, a first swing arm 83, a second swing arm 84, a cylinder 85, a piston 86, an intake pipe 87, a first one-way valve 88, an outlet pipe 89, a second one-way valve 810, and an air distribution component 811. The cylinder 85 and the second motor 81 are fixed to the inner top wall of the bracket 2. The rotating shaft 82 is fixed to the front end of the second motor 81. One end of the first swing arm 83 is fixed to the rotating shaft 82, and the other end of the first swing arm 83 is hinged to the second swing arm 84. The piston 86 is slidably connected inside the cylinder 85. The middle part of the right side wall of the piston 86 is hinged to the second swing arm 84. The lower right side wall of 6 is fixedly connected to the upper end of the connecting rod 10. The lower end of the connecting rod 10 extends out of the cylinder body 85 and is fixedly connected to the first slider 7. The left side of the top wall of the cylinder body 85 is fixedly connected to the air inlet pipe 87. The first one-way valve 88 is set in the air inlet pipe 87. The left side wall of the cylinder body 85 is fixedly connected to the air outlet pipe 89. The second one-way valve 810 is set in the air outlet pipe 89. The bottom end of the air outlet pipe 89 passes through the left side wall of the coagulation tank and extends into the interior of the coagulation tank, where it is fixedly connected to the air distribution component 811. The air distribution component 811 is located below the stirring end of the agitator 5. The contact point between the air outlet pipe 89 and the left side wall of the coagulation tank is sealed. The rotation of the second motor 81 drives the rotating shaft 82 to rotate, causing the first swing arm 83 to rotate. This causes the second swing arm 84 to push and pull the piston 86 left and right. When the piston 86 moves to the left, it forces air from the cylinder 85 into the exhaust pipe 89, which then enters the air distribution component 811 for air distribution. Simultaneously, the connecting rod 10 drives the slider to slide to the left. When the piston 86 moves to the right, it draws air into the cylinder 85 from outside, and the connecting rod 10 drives the slider to slide to the right. Thus, the continuous rotation of the second motor 81 achieves intermittent air supply, and simultaneously drives the agitator 5 to move left and right, performing agitation at different positions. The first one-way valve 88 ensures that air can only enter the cylinder 85 through the intake pipe 87, preventing air from escaping through the intake pipe 87. The second one-way valve 810 ensures that air can only exit through the exhaust pipe 89, preventing air from entering the cylinder 85 through the exhaust pipe 89.

[0041] The air distribution component 811 includes a raised block 8111, an outer ring 8112, an inner ring 8113, and connecting pipes 8114. The raised block 8111 is fixed to the inner bottom wall of the coagulation tank. The outer ring 8112 is fixed to the top of the raised block 8111 and communicates with the air outlet pipe 89. Several connecting pipes 8114 are fixedly connected to the inner side wall of the outer ring 8112. The inner end of each connecting pipe 8114 is fixedly connected to the inner ring 8113. The outer ring 8112 surrounds the inner ring 8113. Several first air distribution holes 8115 are opened at the top of the outer ring 8112, and several second air distribution holes 8116 are opened at the top of the inner ring 8113. The first air distribution holes 8115 are evenly spaced along the circumference of the outer ring 8112, and the second air distribution holes 8116 are evenly spaced along the circumference of the inner ring 8113. The raised block 8111 serves to elevate the coagulation tank. Air enters the outer ring 8112 through the air inlet pipe and is distributed to the inner ring 8113 through the connecting pipe 8114. The air is distributed from different positions through the inner and outer rings 8112, resulting in better air distribution and mixing.

[0042] The system also includes a fixed plate 11, an electric push rod 12, a second slider 13, a connecting rod 14, a vertical plate 15, a first automatic reset switch 16, a second automatic reset switch 17, a cam 18, a first dosing device 19, and a second dosing device 20. A fixed plate 11 is fixed to the upper part of the inner wall of the support 2. A groove 21 is formed on the top of the fixed plate 11, and two second sliders 13 are slidably connected within the groove 21. The two second sliders 13 are connected by a connecting rod 14. A vertical plate 15 is fixed to the top wall of the second sliders 13. A first automatic reset switch 16 is fixed to the left side wall of the right vertical plate 15, and a second automatic reset switch 17 is fixed to the right side wall of the coagulation tank. A first dosing device 19 is connected to the coagulation tank 1, and a second dosing device 20 is fixedly connected to the left side of the top wall of the coagulation tank. A first automatic reset switch 16 is electrically connected to the first dosing device 19, and a second automatic reset switch 17 is electrically connected to the second dosing device 20. An electric push rod 12 is fixed to the top wall of the fixed plate 11, and the left end of the electric push rod 12 is fixedly connected to the upright plate 15 located on the right side. A cam 18 is fixed to the rotating shaft 82 and located in front of the first swing arm 83. The second automatic reset switch 17 and the first automatic reset switch 16 are located on the left and right sides of the cam 18, respectively. The straight-line distance between the first automatic reset switch 16 and the second automatic reset switch 17 is D, and the straight-line distance from the axis of the rotating shaft 82 to the distal end of the cam 18 is d, where D > 2d. In this embodiment, the first dosing device 19 is used to add heavy metal precipitating agent to the coagulation tank 1, and the second dosing device 20 is used to add flocculant to the coagulation tank 1. The positions of the first automatic reset switch 16 and the second automatic reset switch 17 can be adjusted left and right by the electric push rod 12. Initially, the position of the first automatic reset switch 16 is adjusted so that the far end of the cam 18 can touch the first automatic reset switch 16. At this time, the cam 18 will not touch the second automatic reset switch 17 during rotation. The second motor 81 rotates, driving the rotating shaft 82 to rotate, causing the cam 18 to rotate. When the far end of the cam 18 rotates to the first automatic reset switch 16, the first automatic reset switch 16 is pressed, causing the first dosing device 19 to add heavy metal precipitant into the coagulation tank 1. In this way, while the motor is continuously rotating, the cam 18 achieves the effect of intermittent dosing (heavy metal precipitant). When flocculant needs to be added, the electric push rod 12 drives the right-side vertical plate 15 to move to the right, causing the left-side vertical plate 15 to move to the left, which in turn causes the second automatic reset switch 17 to move to the left, so that the distal end of the cam 18 can touch the second automatic reset switch 17. When the distal end of the cam 18 rotates to the second automatic reset switch 17, the second automatic reset switch 17 is pressed, causing the second dosing device 20 to add flocculant into the coagulation tank 1. In this way, while the motor is continuously rotating, the cam 18 achieves the effect of intermittent dosing (flocculation).Thus, by attaching the cam 18 to the rotating shaft 82, and cooperating with the first automatic reset switch 16, the second automatic reset switch 17, the first dosing device 19, the second dosing device 20, and the electric push rod 12, the second motor 81 directly drives the automatic intermittent dosing on demand, greatly improving the flocculation effect. The second motor 81 serves not only as the driving source for air supply but also as the driving source for adjusting the left and right position of the agitator 5, and as the basis for intermittent dosing. This multi-functional combination achieves diverse functions, thereby improving the mixing and coagulation effect in different ways.

[0043] The membrane concentration system includes an NF system 1100, an NF concentrate tank 1200, an RO system 1300, an RO concentrate tank 1400, and an evaporator 1500 connected in sequence. The product water outlets of the NF system 1100 and the RO system 1300 are both connected to the discharge tank 1000, and the condensate outlet of the evaporator 1500 is connected to the microfiltration product water tank 600.

[0044] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heavy metal wastewater treatment system, characterized in that: It includes a wastewater equalization tank, a pH equalization tank, a coagulation reaction equipment, a circulation tank, a microfiltration membrane system, a microfiltration permeate tank, and a membrane concentration system, which are connected in sequence. The sludge outlet of the circulating tank is connected to a sludge tank, and the sludge outlet of the sludge tank is connected to a filter press. The membrane concentration system has a product water outlet and a condensate water outlet. The product water outlet is connected to a discharge tank, and the condensate water outlet flows back to the microfiltration product water tank. The coagulation reaction equipment includes a coagulation tank, a support frame, an inlet pipe, an outlet pipe, a stirrer, a slide rail, a first slider, an air supply assembly, valves, and a connecting rod; The top wall of the coagulation tank is fixed with a support, the slide rail is fixed in the middle of the right side wall inside the support, the first slider is slidably connected to the slide rail, the bottom of the slider is fixed with an agitator, and the agitator's stirring end extends into the coagulation tank. An air supply assembly is fixed to the inner top wall of the support. The air supply end of the air supply assembly is located at the bottom of the coagulation tank and below the stirring end of the agitator. The gas supply assembly has left and right movable ends, which are fixedly connected to the first slider via the connecting rod. An inlet pipe is fixedly connected to the upper left side wall of the coagulation tank, and a discharge pipe is fixedly connected to the lower right side wall of the coagulation tank. A valve is installed on the discharge pipe. The agitator includes a mounting plate, a mounting rod, a first motor, a sealing box, a first stirring shaft, a first stirring blade, a first bearing seat, a first bevel gear, a second bevel gear, a second bearing seat, a second stirring shaft, and a second stirring blade; The bottom wall of the first slider is fixed with an installation plate, the bottom wall of the installation plate is fixed with a first motor and an installation rod, the bottom end of the installation rod is fixed with a sealing box, the center of the bottom wall of the sealing box is fixed with a first bearing seat, the bottom end of the first motor is fixed with a first stirring shaft, the lower part of the first stirring shaft passes through the sealing box and the first bearing seat, and extends into the interior of the coagulation tank where a plurality of first stirring blades are fixed. The bottom wall of the sealed box has upward sloping walls on both the left and right sides. A second bearing seat is fixed to the top of the sloping wall. A second bevel gear is fixed to the top of the second stirring shaft. The first bevel gear is located inside the sealed box and is fixed to the first stirring shaft. The second bevel gear meshes with the first bevel gear. The lower part of the second stirring shaft passes through the sealed box and extends into the interior of the coagulation tank, where several second stirring blades are fixed. The first stirring shaft is vertically arranged, and the first stirring shaft and the second stirring shaft are arranged at an angle. The first stirring blade is perpendicular to the first stirring shaft, and the second stirring blade is perpendicular to the second stirring shaft.

2. The heavy metal wastewater treatment system according to claim 1, characterized in that: The first stirring blade and the second stirring blade are misaligned.

3. The heavy metal wastewater treatment system according to claim 1, characterized in that: The air supply assembly includes a second motor, a rotating shaft, a first swing arm, a second swing arm, a cylinder, a piston, an intake pipe, a first one-way valve, an outlet pipe, a second one-way valve, and an air distribution component; The inner top wall of the bracket is fixed with a cylinder and a second motor; The front end of the second motor is fixed with a rotating shaft, one end of the first swing arm is fixed to the rotating shaft, and the other end of the first swing arm is hinged to a second swing arm. A piston is slidably connected inside the cylinder. The middle part of the right side wall of the piston is hinged to the second rocker arm. The lower part of the right side wall of the piston is fixedly connected to the upper end of the connecting rod. The lower end of the connecting rod extends out of the cylinder and is fixedly connected to the first slider. An intake pipe is fixedly connected to the left side of the top wall of the cylinder, and a first one-way valve is disposed on the intake pipe. An outlet pipe is fixedly connected to the left side wall of the cylinder, and a second one-way valve is disposed on the outlet pipe. The bottom end of the vent pipe passes through the left side wall of the coagulation tank and extends into the interior of the coagulation tank, where it is fixedly connected to an air distribution component. The air distribution component is located below the stirring end of the agitator, and the contact point between the vent pipe and the left side wall of the coagulation tank is sealed.

4. The heavy metal wastewater treatment system according to claim 3, characterized in that: The air distribution component includes a raised block, an outer ring, an inner ring, and a connecting pipe; The inner bottom wall of the coagulation tank is fixed with a raised block, the top of the raised block is fixed with an outer ring, the outer ring is connected to the air outlet pipe, the inner side wall of the outer ring is fixedly connected with a plurality of connecting pipes, the inner end of the connecting pipe is fixedly connected to an inner ring, and the outer ring surrounds the inner ring. The top of the outer ring is provided with a plurality of first air distribution holes, and the top of the inner ring is provided with a plurality of second air distribution holes. The first air distribution holes are distributed at equal intervals along the outer ring circumference, and the second air distribution holes are distributed at equal intervals along the inner ring circumference.

5. The heavy metal wastewater treatment system according to claim 3, characterized in that: It also includes a fixed plate, an electric push rod, a second slider, a connecting rod, a vertical plate, a first automatic reset switch, a second automatic reset switch, a cam, a first dosing device, and a second dosing device; A fixing plate is fixed above the inner sidewall of the bracket. A groove is provided on the top of the fixing plate. Two second sliders are slidably connected in the groove. The two second sliders are connected by a connecting rod. A vertical plate is fixed to the top wall of the second slider. A first automatic reset switch is fixed to the left side wall of the vertical plate on the right side. A second automatic reset switch is fixed to the right side wall of the vertical plate on the left side. A first dosing device is fixedly connected to the right side of the top wall of the coagulation tank. A second dosing device is fixedly connected to the left side of the top wall of the coagulation tank. The first automatic reset switch is electrically connected to the first dosing device. The second automatic reset switch is electrically connected to the second dosing device. An electric push rod is fixed to the top wall of the fixed plate, and the left end of the electric push rod is fixedly connected to the upright plate located on the right side. The cam is fixed to the rotating shaft and located on the front side of the first swing arm. The second automatic reset switch and the first automatic reset switch are located on the left and right sides of the cam, respectively. The straight-line distance between the first automatic reset switch and the second automatic reset switch is D, and the straight-line distance from the axis of the rotating shaft to the distal end of the cam is d, where D > 2d.

6. The heavy metal wastewater treatment system according to claim 1, characterized in that: The membrane concentration system includes an NF system, an NF concentrate tank, an RO system, an RO concentrate tank, and an evaporator connected in sequence. The product water outlets of the NF system and RO system are both connected to the discharge tank, and the condensate outlet of the evaporator is connected to the microfiltration product water tank.

7. A method for treating heavy metal wastewater, characterized in that: The treatment of heavy metal wastewater using the heavy metal wastewater treatment system according to any one of claims 1-6 includes the following steps: Heavy metal wastewater is sent to a wastewater equalization tank to adjust its quality and quantity, and then to a pH equalization tank. Sodium hydroxide is added to the pH equalization tank to adjust the wastewater to a pH of 8.0-9.0, causing some of the metal pollutants in the wastewater to form hydroxide precipitates. After the reaction is complete, the wastewater flows by gravity into a coagulation reactor. Heavy metal trapping agents and flocculants are added to the coagulation reactor in sequence, and after flocculation and sedimentation, the precipitate enters a circulation tank. The sludge at the bottom of the circulation tank is discharged into a sludge tank and sent to a filter press for pressing. The sludge cake is outsourced for treatment. The wastewater in the circulation tank is sent to a microfiltration membrane system for filtration. The resulting permeate is sent to a microfiltration permeate tank and then to a membrane concentration system for concentration and evaporation to obtain crystalline salts. The permeate produced by the membrane concentration system is sent to a discharge tank and discharged after meeting the standards. The condensate produced by the membrane concentration system is sent to the microfiltration permeate tank and, together with the permeate from the microfiltration membrane system, re-enters the membrane concentration system for treatment.

8. The method for treating heavy metal wastewater according to claim 7, characterized in that: The membrane concentration system includes an NF system, an NF concentrate tank, an RO system, an RO concentrate tank, and an evaporator connected in sequence. The effluent from the microfiltration permeate tank enters the NF system for nanofiltration treatment. The concentrate produced by nanofiltration enters the NF concentrate tank and then enters the RO system for reverse osmosis treatment. The concentrate produced by reverse osmosis enters the RO concentrate tank and serves as the raw water for the evaporator. The evaporator evaporates and crystallizes the water to obtain crystalline salt. The condensate produced by the evaporator is sent to the microfiltration permeate tank. The permeate produced by nanofiltration and reverse osmosis enters the discharge tank.

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