Heavy metal wastewater resource treatment system and process

Abstract

The application discloses a heavy metal wastewater resource treatment system and process, and belongs to the field of heavy metal wastewater treatment. The heavy metal wastewater resource treatment system comprises wastewater adjusting tanks, pH adjusting tanks, coagulation reaction equipment, sedimentation tanks and ultrafiltration membrane systems which are sequentially connected. The water outlet of the ultrafiltration membrane system is connected with a nanofiltration membrane system, the concentrated water outlet of the ultrafiltration membrane system is returned to the pH adjusting tank, the concentrated water outlet of the nanofiltration membrane system is connected with an evaporation crystallizer, the water outlet of the nanofiltration membrane system is connected with a chelating resin system, the water outlet of the chelating resin system and the condensed water outlet of the evaporation crystallizer are both connected with a reused water tank, the sludge outlet of the sedimentation tank is connected with a sludge tank, and the sludge outlet of the sludge tank is connected with a filter press. The application realizes zero discharge of heavy metal wastewater, resource recycling of heavy metals and water resources through the design of the stepped treatment unit and the closed loop reuse path, and the load of each treatment unit is stable, and the water quality can meet the high standard of the industry.

Description

Technical Field

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

[0002] With the rapid development of industrial manufacturing, the discharge of heavy metal wastewater has been increasing year by year. Heavy metal wastewater typically contains heavy metal ions such as copper, nickel, chromium, and zinc. These substances are highly toxic, difficult to degrade, and easily accumulate in organisms. If directly discharged into the natural environment, they will seriously pollute water bodies, soil, and other ecological media, disrupting the ecological balance and threatening human health through the food chain. Therefore, the compliant treatment of heavy metal wastewater has become one of the core needs in the field of industrial environmental protection.

[0003] Currently, commonly used industrial processes for treating heavy metal wastewater mainly include single or combined processes such as chemical precipitation, membrane filtration, and resin adsorption. However, existing technologies still have the following shortcomings: 1. Traditional chemical precipitation methods only adjust the pH value to make heavy metal ions form hydroxide precipitates. The removal effect of low concentration heavy metal ions is limited, and the effluent is difficult to consistently meet the stringent discharge standards. In some combined processes, the connection between pretreatment and deep treatment units is poor, which can easily lead to load fluctuations in the subsequent membrane system and resin system, affecting the long-term operational stability.

[0004] 2. Existing processes mostly focus on achieving emission standards, lacking reasonable design for the recycling of wastewater generated during the treatment process. This not only wastes water resources but also increases the load on end-of-pipe treatment. At the same time, most processes do not recover heavy metals in a resource-based manner.

[0005] 3. Existing combined processes often have wastewater discharge at the end of the process, or the recycling paths for concentrated water and condensate are not closed-loop, making it impossible to achieve the environmental protection requirement of zero wastewater discharge. This is especially true in areas with water shortages or stringent environmental standards, where the applicability of traditional processes is limited.

[0006] To address the aforementioned issues, there is an urgent need to develop a heavy metal wastewater resource recovery system that is highly interconnected, has a high degree of resource utilization, and can achieve zero emissions. Summary of the Invention

[0007] The purpose of this invention is to provide a heavy metal wastewater resource utilization treatment system and process to overcome at least one of the above-mentioned defects in the prior art.

[0008] To achieve this objective, the present invention adopts the following technical solution: The heavy metal wastewater resource utilization treatment system provided by this invention includes a wastewater equalization tank, a pH equalization tank, a coagulation reaction device, a sedimentation tank, and an ultrafiltration membrane system connected in sequence. The permeate outlet of the ultrafiltration membrane system is connected to the nanofiltration membrane system, the concentrate outlet of the ultrafiltration membrane system is returned to the pH equalization tank, the concentrate outlet of the nanofiltration membrane system is connected to the evaporator crystallizer, the permeate outlet of the nanofiltration membrane system is connected to the chelating resin system, the outlet of the chelating resin system and the condensate outlet of the evaporator crystallizer are both connected to the recycled water tank, the sludge outlet of the sedimentation tank is connected to the sludge tank, and the sludge outlet of the sludge tank is connected to a filter press.

[0009] Preferably, the coagulation reaction equipment includes a coagulation tank, a first bearing housing, a motor, a first spur gear, a second spur gear, a first stirring shaft, a first stirring blade, a mounting rod, a sealing box, a reverse speed change drive assembly, a second bearing housing, a second stirring shaft, and a second stirring blade. The motor and the first bearing housing are fixed to the top of the coagulation tank. The first spur gear is fixed to the top of the motor. The second spur gear is fixed to the upper part of the first stirring shaft, meshing with the first spur gear. The lower part of the first stirring shaft passes through the first bearing housing and the top wall of the coagulation tank, extending into the interior of the coagulation tank where the first stirring blade is fixed. The inner side of the coagulation tank... A mounting rod is fixed to the wall, and a sealing box is fixed to the mounting rod. A second bearing seat is fixed to the bottom wall of the sealing box. The bottom of the second stirring shaft passes through the second bearing seat and the bottom wall of the sealing box, and extends to the bottom of the sealing box where a second stirring blade is fixed. The second stirring blade is located below the first stirring blade. The second stirring shaft is sealed to the bottom wall of the sealing box. A reverse speed change drive assembly is installed inside the sealing box. The first stirring shaft drives the second stirring shaft to rotate through the reverse speed change drive assembly, so that the rotation direction of the second stirring shaft is opposite to that of the first stirring shaft, and the rotation speed of the second stirring shaft is less than that of the first stirring shaft.

[0010] Preferably, the reverse speed change drive assembly includes a third bearing housing, a first bevel gear, a fourth bearing housing, a rotating shaft, a second bevel gear, a third bevel gear, and a fourth bevel gear. The third bearing housing is fixed to the top wall of the sealed box. The bottom end of the first stirring shaft passes through the top wall of the sealed box and the third bearing housing, and extends to the bottom of the third bearing housing where the first bevel gear is fixed. The first stirring shaft and the top wall of the sealed box are sealed together. The fourth bearing housing is fixed to the right side wall of the sealed box. The right end of the rotating shaft is inserted into the fourth bearing housing. The right part of the rotating shaft is fixed with the second bevel gear, which meshes with the first bevel gear. The left end of the rotating shaft is fixed with the third bevel gear. The upper part of the second stirring shaft is fixed with the fourth bevel gear, which meshes with the third bevel gear.

[0011] Preferably, the tooth ratio of the second bevel gear to the third bevel gear is 2-4:1, and the tooth ratio of the third bevel gear to the fourth bevel gear is 1:1-2.

[0012] Preferably, a number of vertical plates are fixed to the bottom of the first stirring blade, and the number of vertical plates are distributed at intervals along the length direction of the first stirring blade.

[0013] Preferably, the coagulation reaction equipment further includes a dosing component, the dosing component is fixed on the top of the coagulation tank, the first stirring shaft has a first cavity inside, the first stirring blade has a second cavity inside, the second cavity communicates with the first cavity, and the top wall of the first stirring blade has a plurality of first through holes spaced apart along its length direction, and the plurality of first through holes are all inclined outward.

[0014] Preferably, the dosing assembly includes a mounting frame, a heavy metal scavenger dosing tank, a first dosing pump, a first valve, a first dosing pipe, a four-way valve, an extension pipe, a first sealed bearing, a first seal, a PAC dosing tank, a second dosing pump, a second valve, and a second dosing pipe. The mounting frame is fixed to the top of the coagulation tank. The heavy metal scavenger dosing tank is fixed to the left side of the inner top wall of the mounting frame. The first dosing pipe is fixedly connected to the lower right side wall of the heavy metal scavenger dosing tank. The first dosing pipe is equipped with the first dosing pump and the first valve, with the first valve positioned closer to the heavy metal scavenger dosing tank than the first dosing pump. The installation includes a PAC dosing tank fixed to the right side of the top wall inside the mounting frame. A second dosing pipe is fixedly connected to the lower left side wall of the PAC dosing tank. The second dosing pipe is equipped with a second dosing pump and a second valve. The second valve is positioned closer to the PAC dosing tank than the second dosing pump. The first and second dosing pipes are connected by a four-way valve. A first sealing bearing is fixedly installed at the upper part of the first cavity. An extension pipe is fixedly connected to the bottom end of the four-way valve. The bottom end of the extension pipe passes through the first sealing bearing and extends to the lower part of the first cavity. A first seal is provided between the extension pipe and the first cavity.

[0015] Preferably, it also includes an air pump and an air duct. The air pump is fixed in the middle of the top wall of the mounting frame, and the bottom end of the air pump is fixedly connected to the air duct. The bottom end of the air duct is connected to the top end of the four-way valve.

[0016] Preferably, it further includes a PAM dosing tank, a third dosing pump, a third valve, a third dosing pipe, a second sealing bearing, and a second seal. The interior of the second stirring shaft has a third cavity, and the interior of the second stirring blade has a fourth cavity. The fourth cavity communicates with the third cavity. The bottom wall of the second stirring blade has several second through holes spaced apart along its length. The several second through holes are all inclined outwards. The second sealing bearing is fixed above the interior of the third cavity. The PAM dosing tank is fixed to the left side wall of the coagulation tank. One end of the third dosing pipe communicates with the bottom of the PAM dosing tank. The other end of the third dosing pipe passes through the left side wall of the coagulation tank, the left side wall of the sealing box, and the second sealing bearing in sequence, and extends to the lower interior of the third cavity. A second seal is provided between the third dosing pipe and the third cavity. The third dosing pipe is sealed to both the left side wall of the coagulation tank and the left side wall of the sealing box. The third dosing pipe is equipped with a third valve and a third dosing pump. The third valve is positioned closer to the PAM dosing tank than the third dosing pump.

[0017] This invention also provides a heavy metal wastewater treatment process, which uses the above-mentioned heavy metal wastewater resource recovery treatment system, including the following steps: The heavy metal wastewater is fed into a wastewater equalization tank for homogenization; the equalized wastewater is fed into a pH equalization tank to adjust the pH value to 8.0-9.5; the pH-adjusted wastewater is fed into a coagulation reaction device, where heavy metal scavengers, PAC, and PAM are added for mixing, chelation, and flocculation reactions; the coagulated wastewater is fed into a sedimentation tank for solid-liquid separation; the separated sludge is temporarily stored in a sludge tank, dewatered by a filter press, and then outsourced for further treatment; the supernatant from the sedimentation tank is sent to an ultrafiltration membrane system; the concentrated water from ultrafiltration is returned to the pH equalization tank; the permeate from ultrafiltration enters a nanofiltration membrane system; the permeate from the nanofiltration membrane system is fed into a chelating resin system for deep purification; the concentrated water from the nanofiltration membrane system is fed into an evaporator crystallizer; the condensate from the evaporator crystallizer and the effluent from the chelating resin system are fed into a recycled water tank for reuse; and the crystallized salts produced by the evaporator crystallizer are recovered as a resource.

[0018] The beneficial effects of this invention are as follows: 1. Through the design of tiered treatment units and closed-loop reuse paths, zero discharge of heavy metal wastewater and resource recovery of heavy metals and water resources are achieved. Moreover, each treatment unit has a stable load, low operation and maintenance difficulty, and the effluent quality can meet the high standards of the industry.

[0019] 2. Through the graded design of the upper and lower stirring blades with high speed and low speed in opposite directions, it can achieve full mixing and efficient chelation reaction of the reagent and wastewater, and ensure stable growth of flocs. At the same time, it breaks the laminar flow limitation of traditional single-shaft stirring, eliminates mixing dead zones, and greatly improves the mixing uniformity of the coagulation reaction and the heavy metal removal rate.

[0020] 3. The reverse speed change drive assembly achieves two reversals and precise deceleration of power through multi-stage bevel gear meshing transmission, ensuring that the second stirring shaft rotates at a low speed in the opposite direction to the first stirring shaft. Moreover, this assembly is integrated into a sealed box, with precise shaft positioning, good sealing performance, and low power transmission loss. It can effectively prevent water corrosion of transmission components and ensure stable operation of the equipment.

[0021] 4. By combining the tooth ratio of the bevel gears in the reverse speed drive component, the rotation speed ratio of the upper and lower stirring blades is precisely controlled. This ensures the efficiency of rapid mixing and chelation reaction of the upper layer of reagents, while also achieving the gentle coagulation and growth of the lower layer of flocs. This improves the density and settling speed of the flocs, reduces the load of subsequent solid-liquid separation, and stabilizes the quality of the effluent.

[0022] 5. By setting vertical plates at intervals at the bottom of the first stirring blade, a combined disturbance effect of stirring and cutting is formed, which not only enhances turbulence to improve the mixing and chelation efficiency of the agent, but also induces the micro-circulation flow field to break the stratification of the upper and lower flow fields and eliminate the stirring blind zone. Moreover, this design does not significantly increase the stirring resistance and achieves improved mixing uniformity without increasing energy consumption.

[0023] 6. The design of the dosing channel with the cavity built-in of the first stirring shaft and the first stirring blade eliminates the need for external pipelines, simplifying the structure and eliminating dead angles of flow field interference. At the same time, the high-speed rotation centrifugal force of the first stirring blade and the upward and inclined first through hole make the agent evenly sprayed radially into the turbulent zone, which greatly improves the contact area between the agent and the wastewater and the chelation reaction efficiency, achieving efficient and rapid mixing.

[0024] 7. The dosing unit adopts an integrated design of dual dosing tanks, dual pipelines and four-way valves, which can flexibly realize the simultaneous or separate dosing of two agents to adapt to different water quality conditions.

[0025] 8. The four-way valve integrates the agent dosing and aeration mixing branches, and the shared built-in delivery channel simplifies the pipeline structure. Airflow purging can avoid channel blockage and extend the maintenance cycle. In addition, the gas-liquid composite flow field can enhance agent mixing and accelerate the reaction rate. It can flexibly adapt to different water quality conditions through two operating modes.

[0026] 9. The design adopts a dual-shaft internal dosing and staged stirring system. The upper layer uses high-speed stirring to add chelating and coagulant agents for rapid reaction, while the lower layer uses low-speed reverse stirring to precisely add PAM to promote floc coagulation, matching the needs of a step-by-step reaction. The double-sealing design ensures stable operation of the equipment, improves the heavy metal removal rate, and reduces reagent consumption. Attached Figure Description

[0027] Figure 1 This is a system block diagram of the present invention.

[0028] Figure 2 This is a schematic diagram of the coagulation reaction equipment of the present invention.

[0029] Figure 3 This is a cross-sectional structural schematic diagram of the sealing box of the present invention.

[0030] Figure 4 This is a cross-sectional structural diagram of the first stirring shaft and the first stirring blade of the present invention.

[0031] Figure 5 yes Figure 4 A magnified structural diagram of A in the middle.

[0032] Figure 6 This is a partial front view schematic diagram of the dosing component of the present invention.

[0033] Figure 7 This is a cross-sectional view of the second stirring shaft and the second stirring blade of the present invention.

[0034] Figure 8 yes Figure 7 A magnified structural diagram of B in the diagram.

[0035] The labels in the attached diagram are as follows: 100-Wastewater equalization tank, 200-pH equalization tank, 300-Coagulation reaction equipment, 400-Sedimentation tank, 500-Ultrafiltration membrane system, 600-Nanofiltration membrane system, 700-Evaporator crystallizer, 800-Chlorination resin system, 900-Reclaimed water tank, 1000-Sludge tank, 1100-Filter press, 1-Coagulation box, 2-First bearing housing, 3-Motor, 4-First spur gear, 5-Second spur gear, 6-First stirring shaft, 7-First stirring blade, 8-Mounting rod, 9-Reverse speed change drive assembly, 10-Sealed box, 11-Second bearing housing, 12-Second stirring shaft, 13-Second stirring blade, 91-Third bearing housing, 92-First bevel gear, 93-Fourth bearing housing, 94-Rotating shaft, 95-Second bevel gear, 96-Third bevel gear, 9 7-Fourth bevel gear, 14-Vertical plate, 15-Dosing assembly, 16-First cavity, 17-Second cavity, 18-First through hole, 151-Mounting bracket, 152-Heavy metal trapping agent dosing tank, 153-First dosing pump, 154-First valve, 155-First dosing pipe, 156-Four-way valve, 157-Extension pipe, 158-First sealed bearing, 159-First seal, 1510-PAC dosing tank, 1511-Second dosing pump, 1512-Second valve, 1513-Second dosing pipe, 19-Air pump, 20-Air duct, 21-PAM dosing tank, 22-Third dosing pump, 23-Third valve, 24-Third dosing pipe, 25-Second sealed bearing, 26-Second seal, 27-Third cavity, 28-Fourth cavity, 29-Second through hole. Detailed Implementation

[0036] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0037] 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.

[0038] like Figures 1 to 8 As shown, the heavy metal wastewater resource utilization treatment system provided in this embodiment includes a wastewater equalization tank 100, a pH equalization tank 200, a coagulation reaction device 300, a sedimentation tank 400, and an ultrafiltration membrane system 500 connected in sequence. The product water outlet of the ultrafiltration membrane system 500 is connected to the nanofiltration membrane system 600, and the concentrate outlet of the ultrafiltration membrane system 500 is returned to the pH equalization tank 200. The concentrate outlet of the nanofiltration membrane system 600 is connected to the evaporator crystallizer 700, and the product water outlet of the nanofiltration membrane system 600 is connected to the chelating resin system 800. The outlet of the chelating resin system 800 and the condensate outlet of the evaporator crystallizer 700 are both connected to the recycled water tank 900. The sludge outlet of the sedimentation tank 400 is connected to the sludge tank 1000, and the sludge outlet of the sludge tank 1000 is connected to the filter press 1100.

[0039] This embodiment also provides a heavy metal wastewater treatment process, which uses the above-mentioned heavy metal wastewater resource utilization treatment system for treatment, including the following steps: Heavy metal wastewater is fed into wastewater equalization tank 100 for homogenization. The equalized wastewater is then fed into pH equalization tank 200 to adjust the pH to 8.0-9.5. The pH-adjusted wastewater is then fed into coagulation reactor 300, where heavy metal chelating agents, PAC, and PAM are added for mixing, chelation, and flocculation. The coagulated wastewater is then fed into sedimentation tank 400 for solid-liquid separation. The separated sludge is then temporarily stored in sludge tank 1000, dewatered in filter press 1100, and subsequently outsourced for further treatment. The supernatant from pool 400 is sent to ultrafiltration membrane system 500. The concentrate produced by ultrafiltration is returned to pH adjustment pool 200. The permeate produced by ultrafiltration enters nanofiltration membrane system 600. The permeate from nanofiltration membrane system 600 is passed into chelating resin system 800 for deep purification. The concentrate from nanofiltration membrane system 600 is passed into evaporator crystallizer 700. The condensate produced by evaporator crystallizer 700 and the effluent from chelating resin system 800 are passed into recycled water tank 900 for reuse. The crystallized salt produced by evaporator crystallizer 700 is recycled as a resource.

[0040] This invention employs a closed-loop water treatment path—ultrafiltration concentrate recirculation, nanofiltration permeate deep purification, and evaporation condensate reuse—ensuring that all types of wastewater generated during the treatment process are recovered or recycled, ultimately resulting in zero wastewater discharge and fully meeting stringent environmental zero-discharge requirements. Simultaneously, heavy metal ions are removed through a multi-unit synergistic process involving chelation, precipitation, and resin adsorption, ensuring that the effluent heavy metal concentration consistently meets high industry standards, effectively avoiding the pollution risks posed by heavy metals to the ecological environment. On one hand, the crystalline salt obtained from the nanofiltration concentrate through evaporation and crystallization can be directly recycled, preventing the large-scale generation of heavy metal sludge; on the other hand, the purified water collected in the 900-ton reuse tank can be reused as production makeup water, reducing the consumption of fresh water resources. This invention achieves step-by-step water purification through a tiered treatment unit design consisting of a wastewater equalization tank 100, a pH equalization tank 200, a coagulation, sedimentation, membrane system, and resin system, with minimal load fluctuations in each unit. Simultaneously, the design of returning ultrafiltration concentrate to the pH equalization tank 200 utilizes the existing pretreatment foundation of the concentrate while avoiding impact on the upstream homogenization unit, ensuring the long-term stable operation of subsequent units such as coagulation and membrane filtration, and significantly reducing the difficulty of equipment operation and maintenance.

[0041] The coagulation reaction equipment 300 includes a coagulation tank 1, a first bearing seat 2, a motor 3, a first spur gear 4, a second spur gear 5, a first stirring shaft 6, a first stirring blade 7, a mounting rod 8, a sealing box 10, a reverse speed change drive assembly 9, a second bearing seat 11, a second stirring shaft 12, and a second stirring blade 13. The motor 3 and the first bearing seat 2 are fixed to the top of the coagulation tank 1. The first spur gear 4 is fixed to the top of the motor 3. The second spur gear 5 is fixed to the upper part of the first stirring shaft 6, and the second spur gear 5 meshes with the first spur gear 4. The lower part of the first stirring shaft 6 passes through the first bearing seat 2 and the top wall of the coagulation tank 1, and extends into the interior of the coagulation tank 1 where the first stirring blade 7 is fixed. The inner wall of the coagulation tank 1 is fixed... A mounting rod 8 is fixed, and a sealing box 10 is fixed to the mounting rod 8. A second bearing seat 11 is fixed to the bottom wall of the sealing box 10. The bottom of the second stirring shaft 12 passes through the second bearing seat 11 and the bottom wall of the sealing box 10, and extends to the bottom of the sealing box 10 where a second stirring blade 13 is fixed. The second stirring blade 13 is located below the first stirring blade 7. The second stirring shaft 12 is sealed with the bottom wall of the sealing box 10. A reverse speed change drive assembly 9 is disposed inside the sealing box 10. The first stirring shaft 6 drives the second stirring shaft 12 to rotate through the reverse speed change drive assembly 9, so that the rotation direction of the second stirring shaft 12 is opposite to the rotation direction of the first stirring shaft 6, and the rotation speed of the second stirring shaft 12 is less than the rotation speed of the first stirring shaft 6.

[0042] During the mixing operation, the motor 3 starts, driving the first spur gear 4 to rotate, which in turn drives the second spur gear 5 to rotate, which in turn drives the first stirring shaft 6 to rotate, causing the first stirring blade 7 to rotate. This stirs the mixture in the upper middle part of the coagulation tank 1. The first stirring shaft 6 drives the second stirring shaft 12 to rotate in the opposite direction through the reverse speed change drive assembly 9, and reduces the speed of the second stirring shaft 12. This, in turn, drives the second stirring blade 13 to perform low-speed reverse stirring in the lower part of the coagulation tank 1.

[0043] The staged design, combining high-speed stirring by the first stirring blade 7 in the upper layer with low-speed reverse stirring by the second stirring blade 13 in the lower layer, allows for rapid dispersion of reagent clumps in the upper layer, ensuring sufficient contact between the heavy metal chelating agent, PAC, and wastewater for chelation reaction. The low-speed reverse stirring in the lower layer prevents the formed flocs from being destroyed by strong shear forces and promotes floc collision and aggregation through the reverse flow field, achieving an optimal balance between mixing efficiency and flocculation effect. This significantly improves the heavy metal removal rate compared to traditional single-shaft mixing equipment. The bidirectional flow field created by the reverse rotation of the first stirring blade 7 and the second stirring blade 13, combined with the speed difference between the upper and lower layers, breaks the laminar flow limitations of traditional single-shaft mixing, causing the water in the coagulation tank 1 to form a spiral circulation flow. This ensures uniform contact between the reagent and wastewater throughout the entire tank, completely eliminating the problems of insufficient mixing in the upper and middle sections and floc deposition in the lower section, thus improving the overall uniformity of the coagulation reaction.

[0044] The reverse transmission drive assembly 9 includes a third bearing housing 91, a first bevel gear 92, a fourth bearing housing 93, a rotating shaft 94, a second bevel gear 95, a third bevel gear 96, and a fourth bevel gear 97. The third bearing housing 91 is fixed to the top wall of the sealed box 10. The bottom end of the first stirring shaft 6 passes through the top wall of the sealed box 10 and the third bearing housing 91, and extends to the bottom of the third bearing housing 91 where the first bevel gear 92 is fixed. The first stirring shaft 6 is sealed to the top wall of the sealed box 10. The fourth bearing housing 93 is fixed to the right side wall of the sealed box 10. The right end of the rotating shaft 94 is inserted into the fourth bearing housing 93. The right part of the rotating shaft 94 is fixed with the second bevel gear 95, which meshes with the first bevel gear 92. The left end of the rotating shaft 94 is fixed with the third bevel gear 96. The upper part of the second stirring shaft 12 is fixed with the fourth bevel gear 97, which meshes with the third bevel gear 96.

[0045] The rotation of the first stirring shaft 6 drives the first bevel gear 92 to rotate, which in turn drives the second bevel gear 95 to rotate, which in turn drives the rotating shaft 94 to rotate, which in turn drives the third bevel gear 96 to rotate, which in turn drives the fourth bevel gear 97 to rotate, ultimately causing the second stirring shaft 12 to rotate in the opposite direction. Through the multi-stage bevel gear meshing transmission of the first bevel gear 92, second bevel gear 95, rotating shaft 94, third bevel gear 96, and fourth bevel gear 97, the direction of power is reversed twice, ultimately making the rotation direction of the second stirring shaft 12 opposite to that of the first stirring shaft 6. Simultaneously, the tooth ratio of each bevel gear achieves a speed reduction effect, making the speed of the second stirring shaft 12 lower than that of the first stirring shaft 6. The reversal logic is clear, the speed reduction effect is stable, and the power transmission loss is low. The reverse speed drive assembly 9 is integrated into the sealed box 10. The shaft system is precisely positioned through the third bearing seat 91 and the fourth bearing seat 93. It occupies little space and has strong compatibility with the coagulation box 1. The double sealing design of the first stirring shaft 6 and the top wall of the sealed box 10, and the second stirring shaft 12 and the bottom wall of the sealed box 10, effectively isolates water from the transmission components and avoids corrosion and jamming failures.

[0046] The tooth ratio of the second bevel gear 95 to the third bevel gear 96 is 2-4:1, and the tooth ratio of the third bevel gear 96 to the fourth bevel gear 97 is 1:1-2. Through the combined design of the tooth ratios of the second bevel gear 95 and the third bevel gear 96, and the third bevel gear 96 and the fourth bevel gear 97, the rotational speed ratio of the second stirring shaft 12 to the first stirring shaft 6 can be precisely controlled. This allows the first stirring blade 7 in the upper layer to rapidly disperse the reagent flocs at high speed, ensuring sufficient contact between the heavy metal chelating agent, PAC, and wastewater, thus improving the chelation reaction efficiency. Simultaneously, the second stirring blade 13 in the lower layer can stir in the opposite direction at low speed, preventing the flocs from being destroyed by strong shear forces and promoting floc collision and aggregation through a gentle flow field. This results in increased floc density, faster settling speed, significantly reduced solid-liquid separation load in the subsequent sedimentation tank 400, and more stable effluent quality.

[0047] The bottom of the first stirring blade 7 is fixed with several vertical plates 14, which are distributed at intervals along the length of the first stirring blade 7.

[0048] By setting the vertical plate 14, a combined disturbance effect of stirring by the first stirring blade 7 and cutting by the vertical plate 14 is formed when rotating at high speed. The vertical plate 14 can further disperse the incompletely dispersed agent clumps (especially PAC) in the water, while disrupting the laminar flow state of the water and forming denser micro-turbulence. This increases the contact area between the heavy metal trap, PAC and wastewater, resulting in a more complete chelation reaction and avoiding problems such as excessively high local agent concentration or uneven mixing. The local negative pressure formed at the bottom of the first stirring blade 7 when the vertical plate 14 rotates will guide the upper layer of mixed water to flow downwards, while simultaneously driving the lower layer of water to replenish upwards, forming a micro-circulation flow field of upward suction and downward replenishment. Combined with the superposition of the flow fields of the upper and lower layers of reverse variable speed stirring, the flow field stratification between the first stirring blade 7 and the second stirring blade 13 is effectively broken, eliminating the stirring blind zone in the middle and upper parts, and improving the uniformity of water mixing in the entire area of ​​the coagulation tank 1 compared to the design without the vertical plate 14. The design of the vertical plates 14 with spacing ensures the disturbance effect without significantly increasing the stirring resistance and avoiding an increase in the load on motor 3. Without increasing energy consumption, the core function of high-speed mixing in the upper layer is further optimized.

[0049] The coagulation reaction equipment 300 also includes a dosing component 15. The dosing component 15 is fixed on the top of the coagulation tank 1. The first stirring shaft 6 has a first cavity 16 inside. The first stirring blade 7 has a second cavity 17 inside. The second cavity 17 is connected to the first cavity 16. The top wall of the first stirring blade 7 has a number of first through holes 18 spaced apart along its length direction. The number of first through holes 18 are all inclined outward.

[0050] The first cavity 16 inside the first stirring shaft 6 is used directly as the reagent delivery channel, eliminating the need for external dosing pipelines inside the coagulation tank 1. This simplifies the overall structure of the equipment, reduces pipeline installation and maintenance costs, and avoids interference from external pipelines on the mixing flow field, preventing water stagnation dead zones around the pipelines. Several first through holes 18 on the top wall of the first stirring blade 7 are distributed at intervals along the length direction and are inclined outwards. Combined with the centrifugal force of the high-speed rotation of the first stirring blade 7, PAC and heavy metal chelating agents can be radially and uniformly sprayed from the first through holes 18 into the turbulent zone in the upper part of the coagulation tank 1. Compared with the traditional single-point dosing method, the contact area between the reagent and the wastewater is greatly increased, avoiding waste or incomplete reaction caused by excessively high local reagent concentrations, and improving the efficiency of heavy metal chelation reaction. The outward-sloping and upward-facing first through-hole 18 design allows the direction of the agent spray to match the rotation direction of the stirring blade and the direction of the turbulent flow field. The agent droplets can be directly carried by the high-speed water flow and instantly dispersed into the water body. At the same time, in conjunction with the turbulence enhancement effect of the bottom vertical plate 14 of the first stirring blade 7, the mixing time between the agent and the wastewater is further shortened, achieving a highly efficient reaction effect of mixing immediately upon addition and significantly reducing the overall duration of the coagulation reaction.

[0051] The dosing assembly 15 includes a mounting frame 151, a heavy metal scavenger dosing tank 152, a first dosing pump 153, a first valve 154, a first dosing pipe 155, a four-way valve 156, an extension pipe 157, a first sealed bearing 158, a first seal 159, a PAC dosing tank 1510, a second dosing pump 1511, a second valve 1512, and a second dosing pipe 1513. The mounting frame 151 is fixed to the top of the coagulation tank 1. The heavy metal scavenger dosing tank 152 is fixed to the left side of the inner top wall of the mounting frame 151. The first dosing pipe 155 is fixedly connected to the lower right side wall of the heavy metal scavenger dosing tank 152. The first dosing pipe 155 is equipped with the first dosing pump 153 and the first valve 154. The first valve 154 is closer to the heavy metal scavenger dosing tank 151 than the first dosing pump 153. 2. The mounting bracket 151 has a PAC dosing tank 1510 fixed on the right side of the inner top wall. The PAC dosing tank 1510 has a second dosing pipe 1513 fixedly connected to the lower left side wall of the PAC dosing tank 1510. The second dosing pipe 1513 is equipped with a second dosing pump 1511 and a second valve 1512. The second valve 1512 is positioned close to the PAC dosing tank 1510 relative to the second dosing pump 1511. The first dosing pipe 155 and the second dosing pipe 1513 are connected by a four-way valve 156. The upper part of the first cavity 16 has a first sealing bearing 158 fixedly fixed inside. The bottom end of the four-way valve 156 is fixedly connected to an extension pipe 157. The bottom end of the extension pipe 157 passes through the first sealing bearing 158 and extends to the lower part of the first cavity 16. A first seal 159 is provided between the extension pipe 157 and the first cavity 16.

[0052] According to the coagulation reaction requirements, the first dosing pump 153 and the second dosing pump 1511 are started, and the first valve 154 and the second valve 1512 are opened simultaneously. The heavy metal chelating agent flows out from the heavy metal chelating agent dosing tank 152 and is transported to the four-way valve 156 through the first dosing pipe 155. PAC flows out from the PAC dosing tank 1510 and is simultaneously transported to the four-way valve 156 through the second dosing pipe 1513. The two agents achieve initial confluence in the four-way valve 156 (or one dosing line can be started separately according to process requirements). The confluenced agents are transported downward through the extension pipe 157 connected to the bottom of the four-way valve 156, enter the first cavity 16, and finally discharge through the first through hole 18. At this time, the first stirring blade 7 is rotating at high speed. With the help of centrifugal force, the agents are sprayed radially and evenly from the through hole into the turbulent zone in the upper part of the coagulation tank 1, where they are quickly mixed with the wastewater, and the chelation reaction and coagulation reaction are started simultaneously. The combined design of the first sealed bearing 158 and the first seal 159 not only ensures the relative stillness between the extension tube 157 and the high-speed rotating first stirring shaft 6, but also achieves the sealed isolation between the drug delivery channel and the outside world.

[0053] The dosing assembly 15, with its dual dosing tanks, dual pipelines, and four-way valve 156, allows for the simultaneous or separate dosing of heavy metal chelating agents and PAC. It can flexibly adjust the dosing combination and ratio based on the heavy metal concentration and water quality fluctuations in the wastewater, adapting to different treatment requirements. Compared to traditional independent dosing systems, it boasts a high degree of structural integration, reducing equipment space requirements. The agent is transported to the first through-hole 18 via the first cavity 16 within the first stirring shaft 6 and the second cavity 17 within the first stirring blade 7. Combined with the centrifugal force of the high-speed rotation of the first stirring blade 7, it achieves close-range, radial, and inclined spraying. The agent droplets are evenly dispersed and directly enter the turbulent zone, significantly increasing the contact area with wastewater compared to traditional external pipeline single-point dosing. This avoids problems such as excessively high local agent concentrations or uneven mixing, simultaneously improving the efficiency of chelation and coagulation reactions, and reducing agent consumption.

[0054] The system also includes an air pump 19 and an air duct 20. The air pump 19 is fixed in the middle of the top wall of the mounting bracket 151, and the bottom end of the air pump 19 is fixedly connected to the air duct 20. The bottom end of the air duct 20 is connected to the top end of the four-way valve 156. After the chemical is added, the first chemical pump 153, the second chemical pump 1511 and the corresponding valves are closed, and the air pump 19 is started. Air is delivered to the four-way valve 156 through the air duct 20, and then flows along the channels of the extension pipe 157, the first cavity 16 and the second cavity 17, and finally sprayed out at high speed from the first through hole 18. If the process requires simultaneous chemical addition and aeration, the output pressure of the air pump 19 can be adjusted so that the airflow and the chemical are initially mixed in the four-way valve 156, forming a gas-liquid mixture, which is then delivered to the first through hole 18 for spraying. The entrainment effect of the bubbles is used to improve the chemical dispersion efficiency.

[0055] The four-way valve 156 integrates the branch circuits for reagent dosing and aeration mixing, sharing a single extension pipe 157, first cavity 16, second cavity 17, and first through hole 18 as the conveying channel. This eliminates the need for separate air vents or air passages for the aeration function, significantly simplifying the equipment's piping structure, reducing the number of openings in the first stirring blade 7, and lowering the difficulty of machining and sealing. The airflow purging process after reagent dosing utilizes high-speed airflow to flush away residual reagent from the inner walls of the first cavity 16, second cavity 17, and first through hole 18, preventing scaling and blockage at the source. This solves the technical pain point of easy residue buildup in built-in dosing channels, extends the maintenance and cleaning cycle of the through holes, and significantly improves the stability of continuous equipment operation. The microbubble flow formed by the airflow exiting the first through hole 18 superimposes with the mechanical stirring flow field of the first stirring blade 7, creating a composite flow field of mechanical turbulence and bubble disturbance in the upper part of the coagulation tank 1. The rising motion of bubbles drives the water to circulate vertically, breaking the limitations of a purely mechanically stirred horizontal flow field and increasing the contact area between the reagent and the wastewater. Simultaneously, the cutting action of the bubbles further breaks up reagent agglomerates, accelerating the chelation and coagulation reactions and shortening the reaction time. The gas and reagent paths are independently controlled via a four-way valve 156, allowing for flexible selection of two operating modes: reagent-before-gas or simultaneous reagent-gas dosing. For high-concentration wastewater, simultaneous reagent-gas dosing enhances dispersion; for low-concentration wastewater, reagent-before-gas dosing reduces energy consumption and offers greater adaptability.

[0056] This system also includes a PAM dosing tank 21, a third dosing pump 22, a third valve 23, a third dosing pipe 24, a second sealing bearing 25, and a second seal 26. The second stirring shaft 12 has a third cavity 27 inside, and the second stirring blade 13 has a fourth cavity 28 inside, which communicates with the third cavity 27. The bottom wall of the second stirring blade 13 has several second through holes 29 spaced apart along its length, and all the second through holes 29 are inclined outwards. The second sealing bearing 25 is fixed to the upper part inside the third cavity 27, and the PAM dosing tank 2 is fixed to the left side wall of the coagulation tank 1. 1. One end of the third dosing pipe 24 is connected to the bottom of the PAM dosing tank 21. The other end of the third dosing pipe 24 passes through the left side wall of the coagulation tank 1, the left side wall of the sealing tank 10, and the second sealing bearing 25 in sequence, and extends to the lower part of the third cavity 27. A second sealing element 26 is provided between the third dosing pipe 24 and the third cavity 27. The third dosing pipe 24 is sealed to both the left side wall of the coagulation tank 1 and the left side wall of the sealing tank 10. The third dosing pipe 24 is provided with a third valve 23 and a third dosing pump 22. The third valve 23 is located closer to the PAM dosing tank 21 than the third dosing pump 22.

[0057] After the upper chelation reaction is completed, the third dosing pump 22 is started, and the third valve 23 is opened. The PAM solution is transported into the third cavity 27 and the fourth cavity 28 through the third dosing pipe 24. Using the centrifugal force of the low-speed reverse rotation of the second stirring blade 13, PAM is evenly sprayed into the water in the lower part of the coagulation tank 1 from the inclined second through hole 29 on the bottom wall. The second stirring blade 13 rotates in the opposite direction at a speed lower than that of the first stirring shaft 6, forming a gentle flow field. This avoids damaging the small flocs already formed in the upper layer and promotes the collision and aggregation of flocs to form dense large flocs, thereby improving the subsequent sedimentation efficiency. The first sealing bearing 158 and the first seal 159 of the first stirring shaft 6, and the second sealing bearing 25 and the second seal 26 of the second stirring shaft 12, respectively achieve dynamic sealing between the static dosing pipeline and the rotating stirring shaft. At the same time, the sealing of the third dosing pipe 24 with the side wall of the coagulation tank 1 and the sealing tank 10 completely prevents water seepage or chemical leakage, ensuring the stable operation of the transmission components and the dosing channel. The upper layer adds heavy metal chelating agent and PAC, utilizing high-speed stirring to achieve chelation reaction and initial coagulation; the lower layer selectively adds PAM, using low-speed reverse stirring to promote floc aggregation, perfectly matching the step-by-step reaction requirements of chelation, initial coagulation, and floc growth. Compared to traditional single-point mixing and addition, this avoids premature reaction between PAM and the heavy metal chelating agent, preventing agent inactivation, thus improving heavy metal removal rate and floc settling speed. Both upper and lower layer agents are sprayed from inclined orifices by the centrifugal force of rotating impellers, with the spray direction highly matched to the flow field direction. Droplets can be instantly dispersed by the water flow, avoiding waste caused by excessively high local agent concentrations; at the same time, the lower layer PAM addition point is close to the floc formation zone, directly acting on small flocs, reducing agent consumption compared to traditional processes.

[0058] 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 resource utilization treatment system, characterized in that: It includes a wastewater equalization tank, a pH equalization tank, a coagulation reaction equipment, a sedimentation tank, and an ultrafiltration membrane system connected in sequence; The permeate outlet of the ultrafiltration membrane system is connected to the nanofiltration membrane system, and the concentrate outlet of the ultrafiltration membrane system is returned to the pH adjustment tank. The concentrate outlet of the nanofiltration membrane system is connected to the evaporator crystallizer. The permeate outlet of the nanofiltration membrane system is connected to the chelating resin system; The outlet of the chelating resin system and the condensate outlet of the evaporator crystallizer are both connected to the recycled water tank. The sludge outlet of the sedimentation tank is connected to the sludge tank, and the sludge outlet of the sludge tank is connected to a filter press.

2. The heavy metal wastewater resource utilization treatment system according to claim 1, characterized in that: The coagulation reaction equipment includes a coagulation tank, a first bearing housing, a motor, a first spur gear, a second spur gear, a first stirring shaft, a first stirring blade, a mounting rod, a sealing box, a reverse speed change drive assembly, a second bearing housing, a second stirring shaft, and a second stirring blade; The top of the coagulation tank is fixed with a motor and a first bearing seat; A first spur gear is fixed to the top of the motor, and a second spur gear is fixed to the upper part of the first stirring shaft. The second spur gear meshes with the first spur gear. The lower part of the first stirring shaft passes through the first bearing seat and the top wall of the coagulation tank, and extends into the interior of the coagulation tank where the first stirring blade is fixed. An installation rod is fixed to the inner side wall of the coagulation box, and the sealing box is fixed to the installation rod; A second bearing seat is fixed to the bottom wall of the sealed box. The bottom of the second stirring shaft passes through the second bearing seat and the bottom wall of the sealed box, and extends to the bottom of the sealed box where a second stirring blade is fixed. The second stirring blade is located below the first stirring blade. The second stirring shaft is sealed to the bottom wall of the sealed box; The reverse speed change drive assembly is housed inside a sealed box; The first stirring shaft drives the second stirring shaft to rotate via a reverse speed change drive assembly, so that the rotation direction of the second stirring shaft is opposite to that of the first stirring shaft, and the rotation speed of the second stirring shaft is less than that of the first stirring shaft.

3. The heavy metal wastewater resource recovery system according to claim 2, characterized in that: The reverse transmission drive assembly includes a third bearing housing, a first bevel gear, a fourth bearing housing, a rotating shaft, a second bevel gear, a third bevel gear, and a fourth bevel gear; A third bearing seat is fixed to the top wall of the sealed box. The bottom end of the first stirring shaft passes through the top wall of the sealed box and the third bearing seat, and extends to the bottom of the third bearing seat where a first bevel gear is fixed. The first stirring shaft is sealed to the top wall of the sealed box; A fourth bearing seat is fixed to the right side wall inside the sealed box, and the right end of the rotating shaft is inserted into the fourth bearing seat. A second bevel gear is fixed to the right side of the rotating shaft, and the second bevel gear meshes with the first bevel gear; A third bevel gear is fixed to the left end of the shaft; A fourth bevel gear is fixed to the upper part of the second stirring shaft, and the fourth bevel gear meshes with the third bevel gear.

4. The heavy metal wastewater resource utilization treatment system according to claim 3, characterized in that: The tooth ratio between the second bevel gear and the third bevel gear is 2-4:1; The tooth ratio between the third bevel gear and the fourth bevel gear is 1:1-2.

5. The heavy metal wastewater resource recovery system according to claim 2, characterized in that: Several vertical plates are fixed to the bottom of the first stirring blade; Several of the vertical plates are spaced apart along the length of the first stirring blade.

6. The heavy metal wastewater resource utilization treatment system according to claim 2, characterized in that: The coagulation reaction equipment also includes a dosing assembly; A dosing assembly is fixed to the top of the coagulation tank; The first stirring shaft has a first cavity inside; The first stirring blade has a second cavity inside, and the second cavity is in communication with the first cavity; The top wall of the first stirring blade has a plurality of first through holes spaced apart along its length. Several of the first through holes are inclined outwards.

7. The heavy metal wastewater resource utilization treatment system according to claim 6, characterized in that: The dosing assembly includes a mounting frame, a heavy metal scavenger dosing tank, a first dosing pump, a first valve, a first dosing pipe, a four-way valve, an extension pipe, a first sealed bearing, a first seal, a PAC dosing tank, a second dosing pump, a second valve, and a second dosing pipe; The top of the concrete condenser is fixed with a mounting bracket; A heavy metal trapping agent dosing box is fixed to the left side of the inner top wall of the mounting frame; A first dosing pipe is fixedly connected to the lower right side wall of the heavy metal catching agent dosing tank. The first dosing pipe is equipped with a first dosing pump and a first valve. The first valve is positioned close to the heavy metal catching agent dosing tank relative to the first dosing pump. A PAC dosing box is fixed to the right side of the inner top wall of the mounting frame; A second dosing pipe is fixedly connected to the lower left side wall of the PAC dosing tank. The second dosing pipe is equipped with a second dosing pump and a second valve. The second valve is positioned close to the PAC dosing tank relative to the second dosing pump. The first and second dosing pipes are connected by a four-way valve. A first sealing bearing is fixed at the top inside the first cavity; The bottom end of the four-way valve is fixedly connected to an extension tube, the bottom end of which passes through the first sealing bearing and extends to the lower part of the first cavity. A first sealing element is provided between the extension tube and the first cavity.

8. The heavy metal wastewater resource utilization treatment system according to claim 7, characterized in that: It also includes air pumps and air ducts; An air pump is fixed in the middle of the inner top wall of the mounting bracket. The bottom end of the air pump is fixedly connected to an air duct, and the bottom end of the air duct is connected to the top end of a four-way valve.

9. The heavy metal wastewater resource utilization treatment system according to claim 2, characterized in that: It also includes a PAM dosing tank, a third dosing pump, a third valve, a third dosing pipe, a second sealed bearing, and a second seal; The second stirring shaft has a third cavity inside; The second stirring blade has a fourth cavity inside, which is connected to the third cavity; The bottom wall of the second stirring blade has a plurality of second through holes spaced apart along its length; Several of the second through holes are inclined outwards; A second sealed bearing is fixed above the interior of the third cavity; A PAM dosing tank is fixed to the left side wall of the coagulation tank. One end of the third dosing pipe is connected to the bottom of the PAM dosing tank, and the other end of the third dosing pipe passes through the left side wall of the coagulation tank, the left side wall of the sealing tank, and the second sealing bearing in sequence, and extends to the lower part of the third cavity. A second sealing element is provided between the third dosing tube and the third cavity; The third dosing pipe is sealed to both the left side wall of the coagulation tank and the left side wall of the sealed box; The third dosing pipe is equipped with a third valve and a third dosing pump, with the third valve positioned close to the PAM dosing tank relative to the third dosing pump.

10. A heavy metal wastewater treatment process, characterized in that, The treatment of heavy metal wastewater using the resource recovery system according to any one of claims 1-9 includes the following steps: Heavy metal wastewater is fed into a wastewater equalization tank for homogenization. The equalized wastewater is then fed into a pH equalization tank to adjust the pH value to 8.0-9.

5. The pH-adjusted wastewater is then fed into a coagulation reactor, where heavy metal chelating agents, PAC, and PAM are added for mixing, chelation, and flocculation. The coagulated wastewater is then fed into a sedimentation tank for solid-liquid separation. The separated sludge is temporarily stored in a sludge tank, dewatered by a filter press, and then outsourced for further treatment. The supernatant from the sedimentation tank is sent to an ultrafiltration membrane system. The concentrate from ultrafiltration is returned to the pH equalization tank. The permeate from ultrafiltration enters a nanofiltration membrane system. The permeate from the nanofiltration membrane system is fed into a chelating resin system for deep purification. The concentrate from the nanofiltration membrane system is fed into an evaporator crystallizer. The condensate from the evaporator crystallizer and the effluent from the chelating resin system are fed into a recycled water tank for reuse. The crystalline salts produced by the evaporator crystallizer are recovered as a resource.

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