Fluidized bed-double membrane method deep defluorination device and use method

Abstract

The invention discloses a fluidized bed-double membrane method deep defluorination device which comprises a plurality of fluidized bed reactors, water inlets of the fluidized bed reactors are connected with a water inlet pipe through first electromagnetic valves, stainless steel filter screens are arranged at the lower ends of the fluidized bed reactors, and cloth carrier layer seed crystals are arranged below the stainless steel filter screens. A fluidized bed clarification area is arranged above the stainless steel filter screen, a fluidized bed water outlet is connected with an ultrafiltration water inlet of a first ultrafiltration membrane column through a first high-pressure diaphragm pump, an ultrafiltration water outlet of the first ultrafiltration membrane column is communicated with an adjusting tank, and the adjusting tank is connected with a reverse osmosis water inlet of a reverse osmosis membrane column through a second high-pressure diaphragm pump; and a reverse osmosis water outlet of the reverse osmosis membrane column is connected with a water production tank. The fluorine ion concentration of the effluent is far higher than 10mg / L of the GB 30484-2013 battery industry pollutant discharge standard, and stably reaches below 1mg / L, so that the quality of the effluent meets the reuse water standard of the semiconductor industry, and the reuse rate of the industrial water is improved.

Description

Technical Field

[0001] The invention relates to a fluidized bed-double membrane method deep defluorination device and a use method thereof, belonging to the field of sewage treatment. Background Art

[0002] Fluoride-containing wastewater refers to wastewater containing fluoride generated during industrial production. With the continuous acceleration of the global industrialization process, the rapid development of fluorine chemical industry, electronics, metallurgy, steelmaking, aluminum electrolysis, chemical industry, pesticide and other industries has led to an increase in the discharge of fluoride-containing wastewater year by year. The treatment of fluoride-containing wastewater has become an important issue in the current environmental protection field. Since fluoride has high biological toxicity and environmental persistence, if fluoride-containing wastewater is directly discharged without proper treatment, it will cause serious harm to water bodies, soil and human health. The fluorine chemical industry is one of the main sources of fluoride-containing wastewater. In the production process of fluoride salts and hydrofluoric acid, a large amount of fluoride enters the wastewater, resulting in extremely high fluoride ion concentrations in the wastewater, sometimes even up to several thousand milligrams per liter. In the electronic manufacturing process such as semiconductors and electroplating, the generation of fluoride-containing wastewater is inevitable due to the need to use fluorine-containing chemicals. These wastewaters usually contain high concentrations of fluoride ions. In metallurgical and steelmaking processes, especially in aluminum electrolysis and steel production, fluoride is widely used as a flux, resulting in a large amount of fluoride-containing wastewater.

[0003] Fluoride is a strong bioaccumulative toxin that can accumulate through the food chain and cause serious poisoning to aquatic organisms and soil microorganisms. If fluoride-containing wastewater seeps into the soil, fluoride will form insoluble compounds with calcium, magnesium and other ions in the soil, causing damage to the soil structure, affecting the growth of crops, and thus affecting agricultural production. Excessive intake of fluoride by the human body can lead to fluorosis, which in turn causes a series of health problems such as osteoporosis, arthritis, and dental fluorosis. The World Health Organization stipulates that the upper limit of fluoride content in drinking water is 1.5 mg / L, while my country's "Standards for Drinking Water Quality" (GB5749-2022) stipulates that the limit is 1 mg / L.

[0004] For the treatment of fluoride-containing wastewater, the commonly used methods include chemical precipitation, electrochemical method, adsorption method, ion exchange resin method, etc. The chemical precipitation method is to remove fluoride ions from the water by adding chemical agents to the wastewater to react with fluoride and the agent to form insoluble calcium fluoride precipitate. Lime is usually used as a precipitant. However, due to the low solubility of calcium fluoride in water, the removal rate of this method is limited, and the fluoride ion concentration of the treated effluent is usually difficult to meet environmental protection requirements. The electrochemical method uses electrode reaction to remove fluoride ions, which can achieve a higher fluoride removal efficiency, but the equipment cost is usually high and the operation is complicated. It is suitable for some high-precision wastewater treatment occasions. The adsorption method uses adsorbents (such as activated carbon, bauxite, etc.) to adsorb fluoride ions in water, thereby reducing the fluoride content. It has the advantages of simple operation and relatively low cost, but the regeneration of the adsorbent and the disposal of the adsorbent after treatment are still a challenge. The ion exchange method uses ion exchange resin to exchange fluoride ions in wastewater, thereby achieving the purpose of fluoride removal. It has a high fluoride removal effect, but the cost of the resin is high and it needs to be regenerated regularly. It is suitable for treating small amounts of high-concentration fluoride-containing wastewater.

[0005] Although the above-mentioned defluorination methods have been widely used in practical applications, there are still some problems that need to be solved. First, although traditional methods such as chemical precipitation and coagulation sedimentation have low costs, the amount of sludge after treatment is large, the secondary pollution problem is prominent, and the treatment effect is sometimes difficult to meet the emission standards. Secondly, although new technologies such as electrochemical method and ion exchange method have high defluorination efficiency, they are expensive and have limited scope of application. The treatment direction of fluoride-containing wastewater should focus on the development of more efficient, economical and environmentally friendly treatment technologies, combining a combination of multiple treatment methods to achieve efficient treatment of fluoride-containing wastewater of different concentrations and sources. In addition, in the selection of treatment technology, attention should also be paid to the recovery and recycling of resources to further reduce the impact on the environment. Summary of the invention

[0006] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a fluidized bed-double membrane method deep defluorination device and a method of use, the fluoride ion concentration of the effluent is much higher than the 10 mg / L of the battery industry pollutant emission standard GB 30484-2013, and is stably below 1 mg / L, so that the effluent water quality meets the semiconductor industry reuse water standard and improves the reuse rate of industrial water.

[0007] Technical solution: To solve the above technical problems, a fluidized bed-double membrane method deep defluorination device of the present invention comprises a plurality of fluidized bed reactors, the water inlet of the fluidized bed reactor is connected to the water inlet pipe through a first solenoid valve, a stainless steel filter is provided at the lower end of the fluidized bed reactor, a cloth carrier layer seed is provided below the stainless steel filter, a fluidized bed clarification zone is provided above the stainless steel filter, a first high-pressure diaphragm pump is connected to the ultrafiltration water inlet of a first ultrafiltration membrane column at the water outlet of the fluidized bed, the ultrafiltration water outlet of the first ultrafiltration membrane column is connected to a regulating tank, and the regulating tank is connected to the ultrafiltration water outlet of the first ultrafiltration membrane column through a first high-pressure diaphragm pump. The second high-pressure diaphragm pump is connected to the reverse osmosis water inlet of the reverse osmosis membrane column, and the reverse osmosis water outlet of the reverse osmosis membrane column is connected to the water production tank; it also includes a concentrated water tank, the water inlet of the concentrated water tank is connected to the upper end of the ultrafiltration membrane column and the lower end of the reverse osmosis membrane column, the water outlet of the concentrated water tank is connected to the water inlet of the fluidized bed reactor, and a backwash water inlet is provided at the bottom of the water production tank, and the backwash water inlet is connected to the upper end of the reverse osmosis membrane column and the lower end of the ultrafiltration membrane column through the third high-pressure diaphragm pump; the fluidized bed reactor is connected to the precipitant dosing tank through a pipeline, and a stirring device is arranged in the precipitant dosing tank.

[0008] Preferably, the cloth-carrying layer seed crystals comprises several layers of non-woven fabrics, and seed crystal particles are placed on each layer of non-woven fabrics.

[0009] Preferably, the stainless steel filter screen is 100 or 150 mesh.

[0010] Preferably, the ultrafiltration membrane assembly of the ultrafiltration membrane column is an external pressure PVDF ultrafiltration membrane, and the water production of a single branch is 1-4m 3 / h, the operating pressure is below 0.3Mpa, the reverse osmosis membrane component is a polyamide film composite membrane, and the water output of a single branch is 0.25-1.2m 3 / h, the operating pressure is between 0.7-1.0Mpa.

[0011] A method for using a fluidized bed-double membrane deep defluorination device, characterized in that it comprises the following steps: The first step is to determine the seed dosage, seed selection, calcium chloride dosage, and optimal value of fluidized bed rising velocity under the influent concentration, temperature, and pH value through a small test experiment, and put the precipitant calcium chloride and pH regulator sodium hydroxide determined by the small test into the precipitant dosing tank, and after they are fully dissolved under the action of the stirring device, open the water inlet valve on the fluorine-containing wastewater inlet pipe, and introduce the raw water to be treated, and at the same time open the water inlet valve of the lower inlet pipe of the precipitant dosing tank to form a continuous mixed flow in the fluidized bed; In the second step, the raw water to be treated and the precipitant enter the fluidized bed, and heterogeneous crystallization occurs on the seed crystals of the cloth carrier layer. The calcium ions and fluoride ions react on the seed crystals, and then pass through the stainless steel filter. Based on 300 mg / L sodium fluoride feed liquid, the turbidity of the clarified effluent is generally less than 10NTU, and the fluoride ion concentration is generally 10-20 mg / L. The effluent of the fluidized bed enters the ultrafiltration membrane pipeline by gravity, and is pressurized by the first high-pressure diaphragm pump to enter the ultrafiltration membrane column. The number of ultrafiltration membrane components is determined according to the treatment water demand and the water output of a single membrane component. Generally, the total designed water output is not less than 1.2 times the treatment water demand, and the reverse osmosis membrane component is generally not less than 3 times the ultrafiltration membrane. The diameter of the free fluoride ion after passing through the ultrafiltration membrane is 0.266nm, and the effective treatment range of the reverse osmosis membrane is about 0.1nm. A closed stainless steel water regulating tank is set between the ultrafiltration and reverse osmosis units, and the effluent residual pressure enters, and then enters the reverse osmosis membrane column through the second high-pressure diaphragm pump; The third step is to close the water inlet electromagnetic valve of the ultrafiltration membrane column, open the backwash electromagnetic valve at the bottom of the water production tank, and start the third high-pressure diaphragm pump for backwashing. According to the built-in opening and closing cycle of the electromagnetic valve on the backwash branch, the individual membrane components of ultrafiltration or reverse osmosis are cleaned. The water production of other membrane components is not affected during the cleaning process. The backwash water enters the concentrated water tank through the transmembrane residual pressure. After the concentrated water tank reaches half of the storage capacity, the electromagnetic valve at the bottom of the concentrated water tank is opened, and the concentrated water tank is refluxed to the bottom of the fluidized bed through the self-priming pump to form a mixed flow. The calcium chloride dosage of the fluidized bed in step one is optimized through small-scale experiments to match the water quality changes. At this point, the entire treatment system is fully opened, and each section forms a continuous flow system.

[0012] Beneficial effects: Compared with the prior art, the present invention has the following advantages: 1. The fluidized bed-double membrane deep defluorination device of the present invention can achieve a high degree of defluorination. Under the condition of 300 mg / L of sodium fluoride in the inlet water, the fluoride ion concentration in the test effluent is lower than 0.3 mg / L, which is better than the fluoride ion concentration of about 10 mg / L in the effluent of the general multi-stage internal circulation precipitation method and better than the fluoride ion concentration of about 5 mg / L in the effluent of the ion exchange resin.

[0013] 2. The crystal seed configuration effect of the fluidized bed-double membrane method deep defluorination device of the present invention is good. Generally, the fluidized bed defluorination device needs to be equipped with a stirring device to keep the reaction zone in a turbulent state and the crystal seeds do not sink to the bottom, so as to maintain more growth sites of fluoride ions and calcium ions on the surface of the crystal seeds. The present device adopts a carrier crystal seed, and the upward flow formed by the self-priming pump with water inlet at three places is used to grow fine crystal seeds between the layers of non-woven fabrics.

[0014] 3. The fluidized bed-double membrane method deep defluorination device of the present invention has a strong ability to cope with changes in water quality, and the process has many ways to cope with changes in water quality. For example, the pH value in the fluidized bed reaction zone can be adjusted without adding additional facilities, and a variety of crystal seeds can be replaced to remove chromium ions based on the precipitation method. Polyaluminum chloride, calcium carbonate, calcium oxide, calcium hydroxide, sodium hydroxide, etc. can be added to the precipitant addition tank to form a composite precipitate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the present invention.

[0016] Figure 2 Schematic diagram of the structure of the seed carrier layer.

[0017] In the figure: 1-water inlet; 2-horizontal self-priming pump; 3-electromagnetic valve; 4-seed crystals of cloth carrier layer; 5-stainless steel filter; 6-fluidized bed clarification zone; 7-fluidized bed outlet; 8-high-pressure diaphragm pump; 9-ultrafiltration water inlet; 10-ultrafiltration water outlet; 11-ultrafiltration water tank inlet; 12-reverse osmosis water inlet; 13-reverse osmosis water outlet; 14-process water outlet; 15-backwash water inlet; 16-reverse osmosis backwash pipeline; 17-ultrafiltration backwash Pipeline; 18-reverse osmosis backwash drainage; 19-ultrafiltration backwash drainage; 20-concentrated water reflux; 21-precipitant dosing tank; 22-agitator; 23-fluidized bed reactor; 24-ultrafiltration membrane column; 25-reverse osmosis membrane column; 26-adjustment tank; 27-concentrated water tank; 28-water production tank; 29-wastewater inlet pipe system; 30-precipitant dosing pipe system; 31-fluidized bed outlet pipe system; 32-ultrafiltration water production pipe system; 33-reverse osmosis water production pipe system. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings.

[0019] like Figure 1As shown, the fluidized bed-double membrane method deep defluorination device of the present invention includes a fluidized bed reactor, an ultrafiltration membrane unit, an adjustment tank, a reverse osmosis membrane unit, and a concentrated water tank, wherein the fluorine-containing wastewater is connected to the bottom of the fluidized bed reactor through a pipeline, and n-stage parallel fluidized beds are set according to the fluorine-containing wastewater. The present invention sets 4 stages, and the secondary water inlet pipes are distributed respectively. The secondary water inlet pipes are controlled by electromagnetic valves. The bottom of the fluidized bed reactor is also connected to the precipitant dosing tank, and is equipped with a set of self-priming pumps and electromagnetic valves. The bottom of the fluidized bed reactor is also connected to the concentrated water tank, and is also equipped with a set of self-priming pumps and electromagnetic valves. The upper part of the fluidized bed reactor is connected to a high-pressure diaphragm pump, and the pump outlet is connected to 2-6 parallel ultrafiltration membrane columns, the ultrafiltration membrane outlet is connected to the adjustment tank, and the water outlet of the adjustment tank is connected to a high-pressure diaphragm pump, which is connected to 6-18 parallel reverse osmosis membrane columns. A storage tank is set up for the reverse osmosis effluent, which is connected to a self-priming pump as system water production. The bottom of the tank is connected to a high-pressure diaphragm pump, which is connected to the backwash of the ultrafiltration membrane and reverse osmosis membrane units. The backwash outlet is connected to a concentrated water storage tank, and the bottom of the concentrated water storage tank is connected to a pipeline, which flows back to the bottom of the fluidized bed reactor through a self-priming pump. Valves are set on each pipeline to control the pipeline on and off and switch the operation / backwash process.

[0020] The fluidized bed reactor is equipped with a main shell, baffles, cloth-carrying layer crystal seeds, and a stainless steel filter. The cloth-carrying layer crystal seeds cover the reaction zone below the stainless steel filter. The zone above the stainless steel filter is a clarification zone. The lower part is equipped with three water inlets connected to fluorine-containing wastewater, precipitant dosing tanks and membrane concentrated water. The upper part is equipped with a water outlet connected to ultrafiltration water inlet. The stainless steel filter is 100 or 150 mesh. The fluidized bed is generally made of fiberglass or 304 stainless steel. The size of the reaction zone is generally 1500-2500mm in height and 200-300mm in diameter. The size of the clarification zone is 1200-2000mm in height and 600-800mm in diameter.

[0021] The precipitant dosing tank is equipped with a tank body, a stirring device, a self-priming pump, and a liquid level gauge. The bottom is connected to the bottom of the fluidized bed reactor. The general volume is not less than 8m 3 .

[0022] The regulating tank is equipped with a tank body, a level gauge, and an inspection port. The general volume range is 10-20m 3 .

[0023] The ultrafiltration membrane assembly is generally an external pressure PVDF ultrafiltration membrane, and the water production of a single branch is 1-4 m 3 / h, the operating pressure is below 0.3Mpa, the reverse osmosis membrane component is a polyamide film composite membrane, and the water production of a single branch is 0.25-1.2 m 3 / h, the operating pressure is between 0.7-1.0Mpa.

[0024] The water production tank is equipped with a tank body, a liquid level gauge, and a backwash pipeline connected to the bottom. The backwash pipeline is connected to the ultrafiltration backwash pipeline and the reverse osmosis backwash pipeline through a three-way and an electromagnetic valve. The system water production outlet is set at a certain height on the bottom side, with a volume of not less than 5 m 3 , that is, to meet the backwash water volume of each membrane unit.

[0025] The concentrate tank is equipped with a tank body, a liquid level gauge, and a self-priming pump. The concentrate tank is connected to the concentrate of 2-6 parallel ultrafiltration membrane columns and 6-18 parallel reverse osmosis membrane columns.

[0026] The fluidized bed-double membrane method deep defluorination device of the present invention can effectively reduce the fluoride ion concentration to below 0.3 mg / L, effectively improve the removal efficiency of suspended matter, and compared with existing sewage treatment equipment, the water treatment efficiency is higher.

[0027] All pipelines in the present invention are made of polyethylene. The method for using the fluidized bed-double membrane method deep defluorination device of the present invention comprises the following steps: The first step is to determine the seed dosage, seed selection, calcium chloride dosage, and optimal value of fluidized bed rise velocity under specific conditions of influent concentration, temperature, and pH value through small-scale experiments, and to examine the pH value adjustment of the precipitant dosing tank. Generally, the equipment meets the requirements of influent concentration of 50-1000 mg / L, temperature of 10-45°C, and pH value of 2-9. Generally, the seed dosage is per m 3 The fluidized bed reactor is added with 3-15 kg of calcium fluoride or silicon dioxide as the seed. The amount of calcium chloride added depends on the average fluoride ion concentration of the influent water. The calcium-fluoride molar ratio is between 0.8 and 0.5. The fluidized bed rise velocity is about 60-120 mm / min. The water volume treated by each stage of the fluidized bed is about 0.45-0.9 m 3 / h.

[0028] After the dosage of precipitant calcium chloride and pH adjuster sodium hydroxide determined by the small test is added into the precipitant dosing tank, after being fully dissolved under the action of the stirring device, the water inlet valve on the fluorine-containing wastewater inlet pipe is opened, and the raw water to be treated is introduced. At the same time, the water inlet valve of the lower inlet pipe of the precipitant dosing tank is opened to form a continuous mixed flow in the fluidized bed.

[0029] Combination Figure 2Description: By setting a carrier seed in the reaction zone, the reaction zone below the stainless steel filter of the fluidized bed reactor is formed by stacking multiple layers of hydrophilic non-woven fabrics cut in a circular shape, which are generally polyester or polylactic acid materials. Seeds are uniformly added between the non-woven fabric layers. After the fluorine-containing wastewater to be treated enters the bottom of the fluidized bed, it will pass through the non-woven fabric layers layer by layer and react. A stirring device should be set in a conventional fluidized bed reactor to make the mixed flow turbulent to prevent the suspended particle seeds from aggregating and precipitating with each other in the reaction zone, and increase the nucleation sites for the reaction of fluoride ions and calcium ions. The present invention disperses the seeds in the reaction zone by stacking permeable hydrophilic non-woven fabrics, saving a stirring device.

[0030] In the second step, the raw water to be treated and the precipitant enter the fluidized bed, and heterogeneous crystallization occurs in the seed crystals of the cloth carrier layer. The calcium ions and fluoride ions react on the seed crystals, and then pass through the stainless steel filter. The turbidity is further reduced in the clarification area of ​​the fluidized bed. Based on 300 mg / L sodium fluoride feed liquid, the turbidity of the clarified water is generally less than 10NTU, and the fluoride ion concentration is generally 10-20 mg / L. The effluent of the fluidized bed enters the ultrafiltration membrane pipeline by gravity and is pressurized by a diaphragm pump to hydrate the water. The number of ultrafiltration membrane components is determined according to the water treatment demand and the water output of a single membrane component. Generally, the total water output is not less than 1.2 times the water treatment demand, and the reverse osmosis membrane component is generally not less than 3 times the ultrafiltration membrane. The diameter of free fluoride ions after passing through the ultrafiltration membrane is 0.266nm, and the effective treatment range of the reverse osmosis membrane is about 0.1nm. Therefore, in the reverse osmosis deep fluoride removal section, fluoride ions are mainly removed by the size screening effect, and the membrane pollution tendency of the reverse osmosis membrane is relatively large. In actual operation, a margin should be left for the influence of the decrease in the flux of the reverse osmosis membrane on the decrease in the total processing capacity of the system. A closed stainless steel water volume regulating tank is set between the ultrafiltration and reverse osmosis units, and the residual pressure of the effluent enters, and then enters the reverse osmosis membrane assembly through a high-pressure diaphragm pump. The ultrafiltration membrane and the reverse osmosis membrane assembly are prior art, so the specific structural composition of the membrane assembly in the present invention is not repeated.

[0031] The third step is to close the electromagnetic valve of the ultrafiltration membrane assembly, open the backwash electromagnetic valve at the bottom of the water production tank, and start the backwash high-pressure diaphragm pump. According to the built-in opening and closing cycle of the electromagnetic valve on the backwash branch, the individual membrane assembly of ultrafiltration or reverse osmosis is cleaned. The water production of other membrane assemblies is not affected during the cleaning process. The backwash water enters the concentrated water tank through the transmembrane residual pressure. When the concentrated water tank reaches half of the storage capacity, open the electromagnetic valve at the bottom of the concentrated water tank, and return to the bottom of the fluidized bed through the self-priming pump to form a mixed flow. Through small-scale experiments, the amount of calcium chloride added to the fluidized bed in step one is optimized to match the water quality changes. At this point, the entire treatment system is fully opened, and each section forms a continuous flow system.

[0032] The fourth step is to ensure that the effluent quality meets the GB / T 19923-2024 urban sewage recycling and industrial water quality standards. The effluent fluoride ion concentration is much higher than the 10 mg / L of GB 30484-2013 battery industry pollutant emission standard, and is stably below 1 mg / L, so that the effluent quality meets the semiconductor industry reuse water standards and increases the reuse rate of industrial water.

[0033] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fluidized bed-double membrane method deep defluorination device, characterized in that: The invention comprises a plurality of fluidized bed reactors, wherein the water inlet of the fluidized bed reactor is connected to the water inlet pipe through the first solenoid valve, a stainless steel filter is arranged at the lower end of the fluidized bed reactor, a cloth carrier layer seed is arranged below the stainless steel filter, a fluidized bed clarification zone is arranged above the stainless steel filter, a first high-pressure diaphragm pump is connected to the ultrafiltration water inlet of the first ultrafiltration membrane column at the water outlet of the fluidized bed, the ultrafiltration water outlet of the first ultrafiltration membrane column is connected to the regulating tank, and the regulating tank is connected to the reverse osmosis water inlet of the reverse osmosis membrane column through the second high-pressure diaphragm pump. The reverse osmosis water outlet of the reverse osmosis membrane column is connected to the water production tank; it also includes a concentrated water tank, the water inlet of the concentrated water tank is connected to the upper end of the ultrafiltration membrane column and the lower end of the reverse osmosis membrane column, the water outlet of the concentrated water tank is communicated with the water inlet of the fluidized bed reactor, a backwash water inlet is provided at the bottom of the water production tank, and the backwash water inlet is connected to the upper end of the reverse osmosis membrane column and the lower end of the ultrafiltration membrane column through a third high-pressure diaphragm pump; the fluidized bed reactor is connected to the precipitant dosing tank through a pipeline, and a stirring device is arranged in the precipitant dosing tank.

2. The fluidized bed-double membrane method deep defluorination device according to claim 1 is characterized in that: The cloth-carrying layer seed crystals include several layers of non-woven fabrics, and seed crystal particles are placed on each layer of non-woven fabrics.

3. The fluidized bed-double membrane method deep defluorination device according to claim 1 is characterized in that: The stainless steel filter screen is 100 or 150 mesh.

4. The fluidized bed-double membrane method deep defluorination device according to claim 1, characterized in that: The ultrafiltration membrane assembly of the ultrafiltration membrane column is an external pressure PVDF ultrafiltration membrane, and the water production of a single branch is 1-4 m 3 / h, the operating pressure is below 0.3Mpa, the reverse osmosis membrane component is a polyamide film composite membrane, and the water production of a single branch is 0.25-1.2 m 3 / h, the operating pressure is between 0.7-1.0Mpa.

5. A method for using the fluidized bed-double membrane deep defluorination device according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Determine the seed dosage, seed selection, calcium chloride dosage, and optimal value of fluidized bed rising velocity under the influent concentration, temperature, and pH value through small-scale experiments. Put the precipitant calcium chloride and pH regulator sodium hydroxide determined by the small-scale experiment into the precipitant dosing tank. After they are fully dissolved under the action of the stirring device, open the water inlet valve on the fluorine-containing wastewater inlet pipe, introduce the raw water to be treated, and at the same time open the water inlet valve of the lower inlet pipe of the precipitant dosing tank to form a continuous mixed flow in the fluidized bed; (2) The raw water to be treated and the precipitant enter the fluidized bed, where heterogeneous crystallization occurs on the seed crystals of the carrier layer. Calcium ions and fluoride ions react on the seed crystals and then pass through a stainless steel filter. Based on a 300 mg / L sodium fluoride feed solution, the turbidity of the clarified effluent is generally less than 10 NTU, and the fluoride ion concentration is generally 10-20 mg / L. The effluent from the fluidized bed enters the ultrafiltration membrane pipeline by gravity, is pressurized by the first high-pressure diaphragm pump, and enters the ultrafiltration membrane column. The diameter of the free fluoride ion after passing through the ultrafiltration membrane is 0.266 nm. A closed stainless steel water volume regulating tank is set between the ultrafiltration and reverse osmosis units, and the effluent enters the residual pressure, and then enters the reverse osmosis membrane column through the second high-pressure diaphragm pump; (3) Close the water inlet electromagnetic valve of the ultrafiltration membrane column, open the backwash electromagnetic valve at the bottom of the water production tank, and start the third high-pressure diaphragm pump for backwashing. According to the built-in opening and closing cycle of the electromagnetic valve on the backwash branch, clean the individual membrane components of ultrafiltration or reverse osmosis. The cleaning process does not affect the water production of other membrane components. The backwash water enters the concentrated water tank through the transmembrane residual pressure. When the concentrated water tank reaches half of the storage capacity, open the electromagnetic valve at the bottom of the concentrated water tank and return it to the bottom of the fluidized bed through the self-priming pump to form a mixed flow. Through small-scale experiments, optimize the amount of calcium chloride added to the fluidized bed in step 1 to match the water quality changes. At this point, the entire treatment system is fully opened, and each section forms a continuous flow system.

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