Fluorine-containing wastewater recovery treatment equipment and treatment process thereof

Abstract

The application discloses a fluorine-containing wastewater recycling treatment equipment and a treatment process thereof, which comprises a reclaimed water adjusting tank, wherein the reclaimed water adjusting tank is communicated with a pretreatment system, a multi-medium filtering device, an activated carbon filter and a resin softening bed; the resin softening bed is communicated with an ultrafiltration system, a primary reverse osmosis system, a concentrated water reverse osmosis system and a reclaimed water tank; the concentrated water reverse osmosis system is communicated with a water inlet end of the primary reverse osmosis system and an HPRO system; the HPRO system is communicated with a defluorination, desilication and desulfurization system; and the defluorination, desilication and desulfurization system is communicated with an evaporation crystallization device and a sludge treatment system. The fluorine-containing wastewater recycling treatment equipment and the treatment process thereof are combined through a modular process architecture and a switchable treatment unit, can flexibly adjust a treatment path according to real-time water quality changes such as organic matter content and hardness of wastewater, break the limitation of a single traditional equipment process, fully adapt to complex water quality scenes of industrial wastewater, and meet multiple requirements of deep purification, resource recycling and sludge reduction.

Description

Technical Field

[0001] This invention relates to the technical field of fluoride-containing wastewater recovery and treatment, specifically to a fluoride-containing wastewater recovery and treatment device and its treatment process. Background Technology

[0002] With industrial development, the discharge of industrial wastewater is increasing daily. Large amounts of fluoride-containing wastewater are generated during industrial production processes. This wastewater not only contains fluoride ions but also often includes pollutants such as high hardness, high sulfate levels, silicon, and suspended solids. Direct discharge of this wastewater will cause serious environmental pollution and waste a significant amount of water resources. Therefore, recycling and treating industrial wastewater to achieve the circular use of water resources is of great importance.

[0003] Existing fluoride-containing wastewater treatment equipment suffers from problems such as a single treatment process, incomplete pollutant removal, low water resource recovery rate, and large sludge production, making it difficult to meet the needs of deep treatment and recycling of industrial wastewater. To address these issues, existing equipment needs to be improved. Summary of the Invention

[0004] The purpose of this invention is to provide a fluoride-containing wastewater recycling and treatment device and its treatment process, in order to solve the problems mentioned in the background art, such as the existing fluoride-containing wastewater treatment devices having a single treatment process, incomplete pollutant removal, low water resource recovery rate, and large sludge production, which make it difficult to meet the needs of deep treatment and recycling of industrial wastewater.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a fluoride-containing wastewater recovery and treatment device, comprising a greywater equalization tank,

[0006] The greywater equalization tank is used to receive fluoride-containing wastewater and balance its quality and quantity. The greywater equalization tank is connected to the pretreatment system, which in turn is connected to a multi-media filtration device. The multi-media filtration device is filled with a layer of quartz sand and anthracite filter media. It is connected to an activated carbon filter and a resin softening bed via a three-way pipe and a two-position three-way solenoid valve, respectively. The activated carbon filter is connected to the resin softening bed via a connecting pipe. The resin softening bed is connected to an ultrafiltration system, which in turn is connected to a primary reverse osmosis system. The concentrate outlet and primary permeate outlet of the primary reverse osmosis system are connected to the concentrate reverse osmosis system and the reclaimed water tank, respectively. The permeate outlet and concentrate outlet of the concentrate reverse osmosis system are connected to the inlet of the primary reverse osmosis system and the HPRO system, respectively. The HPRO system is equipped with a high-pressure reverse osmosis membrane module. The concentrated water outlet of the HPRO system is connected to a fluoride, silicon, and sulfuric acid removal system. The supernatant outlet and sludge outlet of the fluoride, silicon, and sulfuric acid removal system are connected to an evaporation crystallization device and a sludge treatment system, respectively.

[0007] Preferably, a wastewater inlet pipe is provided on one side of the greywater regulating tank, and a stirring device is provided in the middle of the upper end of the greywater regulating tank. Meanwhile, a booster pump is provided on the conveying pipe provided on the other side of the greywater regulating tank.

[0008] Preferably, the pretreatment system includes a chemical hardening unit, a sulfate removal unit, a fluoride removal unit, a silicon removal unit, and a flocculation unit. Both the chemical hardening unit and the flocculation unit are equipped with a dosing device, which contains sodium carbonate, calcium chloride, magnesium oxide, sodium hydroxide, and flocculants.

[0009] Preferably, the resin softening bed is filled with a special ion exchange resin for adsorbing calcium and magnesium ions.

[0010] Preferably, the ultrafiltration system uses an ultrafiltration membrane module with an average pore size between that of a reverse osmosis membrane and a microporous membrane.

[0011] Preferably, the defluorination, desiliconization and sulfuric acid removal system is equipped with a sulfate removal agent and a defluorination and desiliconization agent dosing device.

[0012] Preferably, the evaporation crystallization device includes a raw liquid tank, a feed pump, a non-condensable steam preheater, a hot water preheater, an evaporation system, a vapor-liquid separator, a compressor system, a crystallization separator, a circulation pump, a discharge pump, a thickener, and a centrifuge. The evaporation system includes a first-effect evaporator and a second-effect evaporator. The compressor system is connected to the steam outlet of the vapor-liquid separator and the shell side of the second-effect evaporator in the evaporation system.

[0013] Preferably, the sludge treatment system includes a sludge pump, a sludge tank, and a plate and frame dewatering machine. The two ends of the sludge pump are connected to the sludge outlet of the defluorination, desiliconization, and sulfuric acid removal system and the sludge tank, respectively, while the sludge tank is connected to the plate and frame dewatering machine.

[0014] A process for recovering and treating fluoride-containing wastewater, characterized by comprising the following steps:

[0015] S1. Wastewater enters the greywater equalization tank through the wastewater inlet pipe. In the tank, it is stirred and mixed by a stirring device to balance the water quality and quantity before being fed into the pretreatment system.

[0016] S2. Pretreatment System: This stage includes chemical hardening, sulfate removal, fluoride removal, and silica removal processes. Chemical softening is used for hardening removal by adding sodium carbonate, calcium chloride, magnesium oxide, and sodium hydroxide via a dosing device. The reaction forms calcium carbonate and magnesium hydroxide precipitates for calcium and magnesium removal. Then, flocculants are added to form large flocs to remove suspended particles, achieving simultaneous hardening and suspended solids removal. This can reduce hardness by 90%. The effluent from the pretreatment system enters the subsequent systems.

[0017] S3. Multi-media filtration device: The device uses filter media such as quartz sand and anthracite to trap suspended impurities in the water. The main function of filtration is to remove suspended or colloidal impurities in the water, especially to effectively remove suspended flocs that cannot be removed by sedimentation technology. Under normal operating conditions, the water from the multi-media filter directly enters the resin softening bed. If the organic matter content in the water is high, the water outlet pipe of the multi-media filter is switched to the activated carbon filter.

[0018] S4. Activated carbon filter: It mainly uses activated carbon organic flocs with high carbon content, large molecular weight and large specific surface area to physically adsorb impurities in water to meet water quality requirements. When water flows through the pores of activated carbon, various suspended particles and organic matter are adsorbed in the pores of activated carbon under the action of van der Waals forces, thereby effectively removing organic matter and meeting the RO membrane's requirements for organic matter in the influent.

[0019] S5. Resin softening bed: It adopts ion exchange technology and uses special resin to achieve the adsorption and ion exchange of multivalent ions such as calcium and magnesium, deeply removing the hardness in wastewater. The resin softened water enters the ultrafiltration system.

[0020] S6. Ultrafiltration System: The average pore size of this system is between that of a reverse osmosis membrane and a microporous membrane. It traps bacteria, viruses, colloids, macromolecules and other particles in the water, while water and low molecular weight solutes permeate through the membrane, greatly reducing the fouling of the reverse osmosis membrane. The ultrafiltration water then enters the first-stage reverse osmosis system.

[0021] S7. First-stage reverse osmosis system: The core of the reverse osmosis system is the reverse osmosis membrane, which is a pressure-driven membrane separation system. Water molecules can pass through the reverse osmosis membrane under pressure, while salt ions cannot pass through the reverse osmosis membrane and are enriched and concentrated on the concentrate side. The first-stage reverse osmosis is designed to have a recovery rate of 70%. The first-stage permeate enters the reclaimed water tank, and the concentrate enters the concentrate reverse osmosis system.

[0022] S8, Concentrate Reverse Osmosis System: The concentrate from the first-stage reverse osmosis is sent to the concentrate reverse osmosis system. The concentrate reverse osmosis is designed to have a recovery rate of 60%. The water produced by this system is returned to the first-stage reverse osmosis system, and the concentrate enters the HPRO system.

[0023] S9, HPRO System: The membrane concentration system adopts the HPRO process to achieve ion concentration. The HPRO membrane (high pressure reverse osmosis membrane) is a form of reverse osmosis. It is resistant to fouling, high pressure, and TDS. It is also resistant to fouling and scaling. The membrane module is easy to clean and can be replaced individually. The HPRO product enters the RO concentrate front end, and the HPRO concentrate enters the defluoridation, desiliconization, and sulfuric acid removal system.

[0024] S10, Fluorine, Silicon and Sulfuric Acid Removal System: Includes sulfate removal, chemical fluorine and silicon removal. In the chemical fluorine and silicon removal process, sulfate removal and fluorine and silicon removal agents are added simultaneously. Sulfate, fluoride ions and silicon dioxide react with the agents to form complex salts, which are removed by flocculation and precipitation.

[0025] S11. The settled sludge is pumped into the sludge tank by the sludge pump, and the supernatant enters the evaporation and crystallization device.

[0026] S12. Evaporation Crystallization Unit: The evaporation crystallization system adopts an MVR forced circulation evaporation crystallizer. The solution comes from the raw liquid tank and is successively transported by the feed pump to the non-condensable steam preheater and hot water preheater. The material temperature is gradually increased from 20℃→25℃→85℃ before being transported to the evaporation system for concentration. The supersaturated concentrate then enters the separator for vapor-liquid separation. The gas generated after flash evaporation enters the compressor system. Due to the evaporation of some water, small crystals will precipitate in the concentrate. The precipitated crystals fall in the crystallization separator and continue to grow. Part of the concentrate is pumped out... The concentrated liquid is returned to the forced circulation evaporator for circulation concentration. When the concentration ratio reaches the required level, a portion of the concentrated liquid is sent to the thickener and centrifuge by the discharge pump. After centrifugation and dehydration, the crystals are bagged and sent out of the evaporation system. The mother liquor after centrifugation is returned to the evaporator or a portion of the accumulated mother liquor is discharged to the drum drying system. When the preheated material enters the evaporator, it undergoes heat exchange and evaporation with the secondary steam that has been compressed to 103°C. The entire system reaches thermal equilibrium. Apart from the need for some fresh steam for preheating, only the compressor motor is needed to maintain the thermal equilibrium of the MVR system evaporation.

[0027] S13. The secondary steam coming out from the top of the separator enters the MVR compression system. After being compressed, the temperature of the secondary steam can be raised to about 103°C. The compressed steam enters the shell side of the first-effect evaporator and the second-effect evaporator as a heat source. The steam heated by the material is condensed into 100°C distilled water and flows to the distilled water tank, which is then pumped out of the boundary area.

[0028] S14. Sludge Treatment System: The sludge generated by the wastewater treatment system enters the sludge treatment system, where it is dewatered by a dewatering machine to reduce its volume, producing sludge with a moisture content of about 60%, which is then transported off-site for disposal.

[0029] Compared with the prior art, the beneficial effects of the present invention are: the fluoride-containing wastewater recovery and treatment equipment and its treatment process,

[0030] (1) By combining the greywater regulating tank with the composite pretreatment system, the quality and quantity of wastewater are first balanced, and then through the synergistic reaction of multiple agents and flocculation sedimentation, pollutants such as hardness, fluoride ions and sulfate are removed simultaneously and efficiently. The hardness removal rate in a single treatment reaches 90%, which solves the problems of poor adaptability to water quality fluctuations and incomplete removal of pollutants in traditional equipment.

[0031] (2) By combining a multi-media filtration device, an activated carbon filter and a resin softening bed, suspended flocs are intercepted, organic matter is adsorbed and calcium and magnesium ions are deeply removed in stages, forming a "three-level pretreatment barrier", which accurately controls the quality of the influent within the tolerance range of the RO membrane, greatly reduces the risk of membrane fouling, and provides stable and high-quality influent for subsequent membrane separation processes.

[0032] (3) By connecting the ultrafiltration system in series with the first-stage reverse osmosis system, the concentrate reverse osmosis system and the HPRO system, the ultrafiltration membrane first intercepts large molecular impurities to protect the reverse osmosis membrane, and then the three-stage membrane separation is used for step-by-step concentration and recovery. The first-stage RO recovery rate is 70% and the concentrate RO recovery rate is 60%, which is more than 30% higher than the traditional single membrane system, thus maximizing the utilization of water resources.

[0033] (4) By combining the defluorination, desiliconization and sulfuric acid removal system with the MVR forced circulation evaporation crystallization device, the pollutants that are easy to scale in the concentrated water are removed first, and then the evaporation crystallization process of gradient preheating and steam recycling is used to realize the resource recovery of crystals and the reuse of distilled water. At the same time, the scale and blockage of the evaporator are avoided, and the dual goals of zero discharge of concentrated water and resource recovery are achieved.

[0034] (5) By combining modular process architecture with switchable treatment units (multi-media / activated carbon filtration), the treatment path can be flexibly adjusted according to real-time water quality changes such as organic matter content and hardness of wastewater, breaking the limitations of the single process of traditional equipment, fully adapting to complex water quality scenarios of industrial wastewater, and meeting the diverse needs of deep purification, resource recovery, and sludge reduction. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall front view of the present invention;

[0036] Figure 2 This is a front view schematic diagram of the water regulating tank in this invention;

[0037] Figure 3 This is a front view structural diagram of the pretreatment system and multi-media filtration device of the present invention;

[0038] Figure 4 This is a front view schematic diagram of the multi-media filtration device, activated carbon filter, and resin softening bed of the present invention.

[0039] Figure 5 This is a schematic diagram of the working process of the evaporation crystallization apparatus of the present invention;

[0040] Figure 6 This is a schematic diagram of the processing technology of the present invention.

[0041] In the diagram: 1. Greywater equalization tank; 101. Wastewater inlet pipe; 102. Stirring device; 103. Delivery pipe; 104. Booster pump; 2. Pretreatment system; 201. Dosing device; 3. Multi-media filtration device; 301. T-junction pipe; 302. Two-position three-way solenoid valve; 4. Activated carbon filter; 401. Connecting pipe; 5. Resin softening bed; 6. Ultrafiltration system; 7. First-stage reverse osmosis system; 8. Concentrate reverse osmosis system; 9. Reclaimed water tank; 10. HPRO system; 11. Defluoridation, desiliconization, and sulfuric acid removal system; 12. Evaporation crystallization device; 13. Sludge treatment system. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Please see Figures 1-6 This invention provides a technical solution: a fluoride-containing wastewater recovery and treatment device and its treatment process, based on... Figure 1 , Figure 2 , Figure 3 and Figure 6 As shown, the greywater equalization tank 1 is used to receive fluoride-containing wastewater and balance the water quality and quantity. The greywater equalization tank 1 is connected to the pretreatment system 2. A wastewater inlet pipe 101 is provided on one side of the greywater equalization tank 1, and a stirring device 102 is provided in the middle of the upper end of the greywater equalization tank 1. Meanwhile, a booster pump 104 is provided on the conveying pipe 103 provided on the other side of the greywater equalization tank 1. The pretreatment system 2 includes a chemical hardening unit, a sulfate removal unit, a fluoride removal unit, a silica removal unit, and a flocculation unit. Both the chemical hardening unit and the flocculation unit are equipped with a dosing device 201. The dosing device 201 contains sodium carbonate, calcium chloride, magnesium oxide, sodium hydroxide, and flocculants.

[0044] according to Figure 1 , Figure 3 , Figure 4 and Figure 6As shown, the pretreatment system 2 is connected to the multi-media filter device 3. The multi-media filter device 3 is filled with a layer of quartz sand and anthracite filter media. The multi-media filter device 3 is connected to the activated carbon filter 4 and the resin softening bed 5 through a three-way pipe 301 and a two-position three-way solenoid valve 302, respectively. At the same time, the activated carbon filter 4 is connected to the resin softening bed 5 through a connecting pipe 401. The resin softening bed 5 is filled with a special ion exchange resin for adsorbing calcium and magnesium ions. The resin softening bed 5 is connected to the ultrafiltration system 6, and the ultrafiltration system 6 is connected to the first-stage reverse osmosis system 7. The ultrafiltration system 6 uses an average... An ultrafiltration membrane module with a pore size between that of a reverse osmosis membrane and a microporous membrane is used. The concentrate outlet and the primary product water outlet of the first-stage reverse osmosis system 7 are connected to the concentrate reverse osmosis system 8 and the reclaimed water tank 9, respectively. The product water outlet and the concentrate outlet of the concentrate reverse osmosis system 8 are connected to the inlet of the first-stage reverse osmosis system 7 and the HPRO system 10, respectively. The HPRO system 10 is equipped with a high-pressure reverse osmosis membrane module, and the concentrate water outlet of the HPRO system 10 is connected to the defluorination, desiliconization and sulfuric acid removal system 11. The defluorination, desiliconization and sulfuric acid removal system 11 is equipped with a sulfate removal agent and a defluorination and desiliconization agent dosing device.

[0045] according to Figure 1 , Figure 5 and Figure 6 As shown, the supernatant outlet and sludge outlet of the defluorination, desiliconization, and sulfuric acid removal system 11 are connected to the evaporation crystallization device 12 and the sludge treatment system 13, respectively. The evaporation crystallization device 12 includes a raw liquid tank, a feed pump, a non-condensable steam preheater, a hot water preheater, an evaporation system, a vapor-liquid separator, a compressor system, a crystallization separator, a circulation pump, a discharge pump, a thickener, and a centrifuge. The evaporation system includes a first-effect evaporator and a second-effect evaporator. The compressor system is connected to the steam outlet of the vapor-liquid separator and the shell side of the second-effect evaporator in the evaporation system. The sludge treatment system 13 includes a sludge pump, a sludge tank, and a plate and frame dewatering machine. The two ends of the sludge pump are connected to the sludge outlet and the sludge tank of the defluorination, desiliconization, and sulfuric acid removal system 11, respectively. The sludge tank is connected to the plate and frame dewatering machine.

[0046] A process for recovering and treating fluoride-containing wastewater, characterized by comprising the following steps:

[0047] S1. Wastewater enters the greywater equalization tank 1 through the wastewater inlet pipe 101. In the tank, it is stirred and mixed by the stirring device 102 to balance the water quality and quantity, and then enters the pretreatment system 2.

[0048] S2, Pretreatment System 2: This stage includes chemical hardening removal, sulfate removal, fluoride removal, and silica removal processes. Chemical softening is used for hardening removal. Sodium carbonate, calcium chloride, magnesium oxide, and sodium hydroxide are added through dosing device 201, reacting to form calcium carbonate and magnesium hydroxide precipitates for calcium and magnesium removal. Then, flocculants are added to form large flocs to remove suspended particles, achieving simultaneous hardening and suspended solids removal. This can reduce hardness by 90%. The effluent from Pretreatment System 2 enters the subsequent systems.

[0049] S3, Multi-media filtration device 3: The device uses filter media such as quartz sand and anthracite to intercept suspended impurities in the water. The main function of filtration is to remove suspended or colloidal impurities in the water, especially to effectively remove suspended flocs that cannot be removed by sedimentation technology. Under normal operating conditions, the water from the multi-media filter directly enters the resin softening bed 5. If the organic matter content in the water is high, the water outlet pipe of the multi-media filter is switched to the activated carbon filter 4.

[0050] S4, Activated Carbon Filter 4: It mainly uses activated carbon organic flocs with high carbon content, large molecular weight and large specific surface area to physically adsorb impurities in water to meet water quality requirements. When water flows through the pores of activated carbon, various suspended particles and organic matter are adsorbed in the pores of activated carbon under the action of van der Waals forces, thereby effectively removing organic matter and meeting the RO membrane's requirements for organic matter in the influent.

[0051] S5, Resin Softening Bed 5: Using ion exchange technology, special resin is used to achieve the adsorption and ion exchange of multivalent ions such as calcium and magnesium, deeply removing hardness from wastewater. The resin-softened water enters the ultrafiltration system 6.

[0052] S6, Ultrafiltration System 6: The average pore size of this system is between that of the reverse osmosis membrane and the microporous filter membrane. It traps bacteria, viruses, colloids, macromolecules and other particles in the water, while water and low molecular weight solutes permeate through the membrane, greatly reducing the fouling degree of the reverse osmosis membrane. The ultrafiltration water enters the first-stage reverse osmosis system 7.

[0053] S7, First-stage reverse osmosis system 7: The core of the reverse osmosis system is the reverse osmosis membrane, which is a pressure-driven membrane separation system. Water molecules can pass through the reverse osmosis membrane under pressure, while salt ions cannot pass through the reverse osmosis membrane and are enriched and concentrated on the concentrate side. The first-stage reverse osmosis is designed to have a recovery rate of 70%. The first-stage product water enters the reclaimed water tank 9, and the concentrate enters the concentrate reverse osmosis system 8.

[0054] S8, Concentrate Reverse Osmosis System 8: The concentrate from the first-stage reverse osmosis is sent to the concentrate reverse osmosis system 8. The designed recovery rate of the concentrate reverse osmosis is 60%. The water produced by this system is returned to the first-stage reverse osmosis system 7, and the concentrate enters the HPRO system 10.

[0055] S9, HPRO System 10: The membrane concentration system adopts the HPRO process to achieve ion concentration. The HPRO membrane (high pressure reverse osmosis membrane) is a form of reverse osmosis. It is resistant to fouling, high pressure, and TDS. It is also resistant to fouling and scaling. The membrane module is easy to clean and can be replaced individually. The HPRO product enters the RO concentrate front end, and the HPRO concentrate enters the defluoridation, desiliconization and sulfuric acid removal system 11.

[0056] S10, Fluorine, Silicon and Sulfuric Acid Removal System 11: Includes sulfate removal, chemical fluorine and silicon removal, wherein the chemical fluorine and silicon removal process simultaneously adds sulfate removal and fluorine and silicon removal agents, sulfate, fluoride ions and silicon dioxide react with the agents to form complex salts, which are removed by flocculation and precipitation;

[0057] S11. The settled sludge is pumped into the sludge tank by the sludge pump, and the supernatant enters the evaporation and crystallization device 12.

[0058] S12, Evaporation Crystallization Unit 12: The evaporation crystallization system adopts an MVR forced circulation evaporation crystallizer. The solution comes out of the raw liquid tank and is successively transported by the feed pump to the non-condensable steam preheater and the hot water preheater. The material temperature is gradually increased from 20℃→25℃→85℃ before being transported to the evaporation system for concentration. The supersaturated concentrate then enters the separator for vapor-liquid separation. The gas generated after flash evaporation enters the compressor system. Due to the evaporation of some water, small crystals will precipitate in the concentrate. The precipitated crystals fall in the crystallization separator and continue to grow. Part of the concentrate is pumped... The concentrated liquid is returned to the forced circulation evaporator for circulation and concentration. When the concentration ratio reaches the required level, a portion of the concentrated liquid is sent to the thickener and centrifuge by the discharge pump. After centrifugation and dehydration, the crystals are bagged and sent out of the evaporation system. The mother liquor after centrifugation is returned to the evaporator or a portion of the accumulated mother liquor is discharged to the drum drying system. When the preheated material enters the evaporator, it undergoes heat exchange and evaporation with the secondary steam that has been compressed to 103°C. The entire system reaches thermal equilibrium. Apart from the need for some fresh steam for preheating, only the compressor motor is needed to maintain the thermal equilibrium of the MVR system evaporation.

[0059] S13. The secondary steam coming out from the top of the separator enters the MVR compression system. After being compressed, the temperature of the secondary steam can be raised to about 103°C. The compressed steam enters the shell side of the first-effect evaporator and the second-effect evaporator as a heat source. The steam heated by the material is condensed into 100°C distilled water and flows to the distilled water tank, which is then pumped out of the boundary area.

[0060] S14, Sludge Treatment System 13: The sludge generated by the wastewater treatment system enters the sludge treatment system 13, where it is dewatered by a dewatering machine to reduce the sludge volume, producing sludge with a moisture content of about 60%, which is then transported off-site for disposal.

[0061] The terms “center,” “longitudinal,” “lateral,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are merely simplified descriptions for the convenience of describing the present invention 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. Therefore, they should not be construed as limiting the scope of protection of the present invention.

[0062] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for recovering and treating fluoride-containing wastewater, characterized in that, Includes the following steps: S1. Wastewater enters the greywater regulating tank (1) through the wastewater inlet pipe (101). It is stirred and mixed in the tank by the stirring device (102) to balance the water quality and quantity before being lifted into the pretreatment system (2). S2, Pretreatment System (2): This stage includes chemical hardening, sulfate removal, fluoride removal, and silicon removal processes. Chemical softening is used to remove hardening. Sodium carbonate, calcium chloride, magnesium oxide, and sodium hydroxide are added through the dosing device (201) to react and form calcium carbonate and magnesium hydroxide precipitates for calcium and magnesium removal. Then, flocculants are added to form large flocs to remove suspended particles, achieving simultaneous hardening and suspended solids removal, reducing hardness by 90%. The effluent from the pretreatment system (2) enters the subsequent system. S3, Multi-media filtration device (3): The device uses quartz sand and anthracite filter media layers to intercept suspended impurities in the water. The main function of filtration is to remove suspended and colloidal impurities in the water as well as suspended flocs that cannot be removed by sedimentation technology. Under normal working conditions, the water from the multi-media filtration device (3) directly enters the resin softening bed (5). If the organic matter content in the water is high, the water outlet pipe of the multi-media filtration device is switched to the activated carbon filter (4). S4, Activated Carbon Filter (4): It mainly uses activated carbon organic flocs with high carbon content, large molecular weight and large specific surface area to physically adsorb impurities in water to meet water quality requirements. When water flows through the pores of activated carbon, various suspended particles and organic matter are adsorbed in the pores of activated carbon under the action of van der Waals forces, thereby effectively removing organic matter and meeting the RO membrane's requirements for organic matter in the water. S5, Resin Softening Bed (5): Using ion exchange technology, calcium and magnesium multivalent ions are adsorbed and exchanged through special resin to deeply remove hardness from wastewater. The resin-softened water enters the ultrafiltration system (6). S6, Ultrafiltration System (6): The average pore size of this system is between that of the reverse osmosis membrane and the microporous filter membrane. It intercepts bacteria, viruses, colloids and large molecular particles in the water, while water and low molecular weight solutes permeate through the membrane, greatly reducing the fouling degree of the reverse osmosis membrane. The ultrafiltration water enters the first-stage reverse osmosis system (7). S7, First-stage reverse osmosis system (7): The core of the reverse osmosis system is the reverse osmosis membrane, which is a pressure-driven membrane separation system. Water molecules pass through the reverse osmosis membrane under pressure, while salt ions cannot pass through the reverse osmosis membrane and are enriched and concentrated on the concentrate side. The first-stage reverse osmosis is designed to have a recovery rate of 70%. The first-stage product water enters the reclaimed water tank (9), and the concentrate enters the concentrate reverse osmosis system (8). S8, Concentrate Reverse Osmosis System (8): The concentrate from the first-stage reverse osmosis is sent to the concentrate reverse osmosis system (8). The designed recovery rate of the concentrate reverse osmosis is 60%. The water produced by this system is returned to the first-stage reverse osmosis system (7), and the concentrate enters the HPRO system (10). S9, HPRO system (10): The membrane concentration system adopts the HPRO process to achieve ion concentration. The HPRO membrane is a form of reverse osmosis. It is resistant to high pressure, TDS, fouling and scaling. The membrane module is easy to clean and can be replaced individually. The HPRO permeate enters the concentrated water RO front end, and the HPRO concentrated water enters the defluoridation, desiliconization and sulfate removal system (11). S10, Fluorine, Silicon and Sulfate Removal System (11): Includes sulfate removal, chemical fluorine and silicon removal, wherein the chemical fluorine and silicon removal process simultaneously adds sulfate removal and fluorine and silicon removal agents, sulfate, fluoride ions and silicon dioxide react with the agents to form complex salts, which are removed by flocculation and precipitation. S11. The settled sludge is pumped into the sludge tank by the sludge pump, and the supernatant enters the evaporation crystallization device (12). S12, Evaporation Crystallization Unit (12): The evaporation crystallization system adopts an MVR forced circulation evaporation crystallizer. The solution comes out of the raw liquid tank and is successively transported by the feed pump to the non-condensable steam preheater and the hot water preheater. The material temperature gradually changes from 20℃→25℃→85℃ before being transported to the evaporation system for concentration. The supersaturated concentrate then enters the separator for vapor-liquid separation. The gas generated after flash evaporation enters the compressor system. Because some water is evaporated, small crystals will precipitate in the concentrate. The precipitated crystals fall in the crystallization separator and continue to grow. Part of the concentrate is then processed by the separator. The pump returns to the forced circulation evaporator for circulation concentration. When the concentration ratio reaches the required level, a portion of the concentrated liquid is sent to the thickener and centrifuge by the discharge pump. After centrifugation and dehydration, the crystals are bagged and sent out of the evaporation system. The mother liquor after centrifugation is returned to the evaporator or a portion of the accumulated mother liquor is discharged to the drum drying system. When the preheated material enters the evaporator, it undergoes heat exchange and evaporation with the secondary steam that has been compressed to 103°C. The entire system reaches thermal balance. Apart from the need for some fresh steam for preheating, only the compressor motor is needed to maintain the thermal balance of the MVR system evaporation. S13. The secondary steam coming out from the top of the separator enters the MVR compression system. After being compressed, the temperature of the secondary steam rises to 103°C. The compressed steam enters the shell side of the first-effect evaporator and the second-effect evaporator as a heat source. The steam after heating the material condenses into 100°C distilled water and flows to the distilled water tank, which is then pumped out of the boundary area. S14, Sludge Treatment System (13): The sludge generated by the wastewater treatment system enters the sludge treatment system (13), is dewatered by a dewatering machine, and undergoes sludge reduction treatment to produce sludge with a water content of 60%, which is then transported off-site for disposal.

Images