Dynamic membrane filtration system for fluorine-containing wastewater treatment and resource recovery and operation method

Abstract

The invention relates to a dynamic membrane filtration system for fluorine-containing wastewater treatment and resource recovery and an operation method. The dynamic membrane filtration system comprises a dynamic membrane filter, a clear water tank, a raw water tank, a pre-coating solution tank and a gas supply module. The pre-coating solution forms a dynamic membrane on the outer surface of the filter cloth after being input into the raw water chamber, fluoride in the fluorine-containing wastewater is intercepted by the dynamic membrane, and purified water enters the purified water temporary storage chamber through the dynamic membrane and then is output to the purified water tank. The defluorination filtration cycle of the dynamic membrane filtration system consists of four stages, namely a pre-coating stage, a defluorination stage and a drainage drying stage. Compared with the prior art, the fluorine-containing wastewater treatment effect and the fluoride recovery efficiency can be effectively improved, and the investment and the cost of a fluorine-containing wastewater treatment system are reduced.

Description

A dynamic membrane filtration system and its operation method for fluoride-containing wastewater treatment and resource recovery. Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a dynamic membrane filtration system and its operation method for treating and recovering fluoride-containing wastewater. Background Technology

[0002] Fluorine is a harmful chemical element, especially when present in water. It is easily absorbed by aquatic organisms, enters the food chain, and ultimately affects human health. Long-term exposure to fluoride-containing wastewater or drinking fluoride-contaminated water can lead to a range of health problems, such as fluorosis, bone diseases, and dental fluorosis. Fluorine also has a profound impact on the ecological environment, such as its toxicity to aquatic plants and animals, disrupting the ecological balance of aquatic bodies, and affecting biodiversity.

[0003] With economic development and industrialization, the problem of industrial wastewater discharge has become increasingly serious. In some industrial parks, fluoride-containing wastewater pollution has become a major challenge for local environmental protection. Because fluorides are extremely stable in water, they are difficult to degrade naturally even after a long period. Even after the pollution source is controlled, the polluted water body is difficult to restore to normal quality. This means that the environmental impact of fluoride-containing wastewater pollution is long-term and irreversible.

[0004] Fluoride-containing wastewater mainly originates from specific industrial production processes, such as the fluorochemical industry (using large amounts of fluoride-containing raw materials, such as hydrofluoric acid and fluorides), the electronics and semiconductor industry (using hydrofluoric acid and ammonium fluoride in chip manufacturing, etching, and cleaning processes), the metal processing and smelting industry (using fluorides as additives or coolants), the new energy industry (using fluoride-containing materials in lithium battery production and photovoltaic manufacturing), the electroplating industry (using fluoride-containing additives in electroplating solutions), the rare earth metal smelting industry (smelting rare earth ores such as fluorocarbon cerium ore), the pharmaceutical industry (using fluoride-containing reagents in some drug synthesis processes), and the silicon-based electrical parts cleaning industry (using fluoride-containing solvents in semiconductor device cleaning). Many of these industries are key pillars and priority industries for national development, creating a significant demand for fluoride usage and the treatment of fluoride-containing wastewater.

[0005] Furthermore, the presence of fluoride in wastewater often mixes with other harmful substances, increasing the difficulty of wastewater treatment. Common technologies for treating fluoride-containing wastewater include physical adsorption, chemical precipitation, ion exchange, and membrane separation. Physical adsorption and chemical precipitation cannot achieve deep fluoride removal to meet the requirements of the "Surface Water Environmental Quality Standard." While ion exchange and membrane separation can remove fluoride effectively, their high investment and maintenance costs make them unsustainable once the volume of fluoride-containing wastewater exceeds a certain scale. Additionally, none of these common technologies can effectively recover the separated fluoride.

[0006] Therefore, it is necessary to develop a treatment technology that can efficiently remove fluorides from fluoride-containing wastewater, effectively recover fluorine, and is technically and economically reliable. Summary of the Invention

[0007] The purpose of this invention is to overcome at least one of the defects of the existing technology, namely, the inability to perform deep defluorination, the lack of sustainability of the defluorination process, and the inability to effectively recover the separated fluorine elements, and to provide a dynamic membrane filtration system and operating method for the treatment of fluoride-containing wastewater and resource recovery.

[0008] The objective of this invention can be achieved through the following technical solution: This invention first provides a dynamic membrane filtration system for the treatment and resource recovery of fluoride-containing wastewater. The dynamic membrane filtration system includes: a dynamic membrane filter for treating fluoride-containing wastewater; a purification tank for storing the treated fluoride-containing wastewater; a raw water tank for inputting fluoride-containing wastewater into the dynamic membrane filter and / or recovering fluoride-containing wastewater from the dynamic membrane filter; a pre-coating solution tank for inputting a pre-coating solution into the dynamic membrane filter to form a dynamic membrane and / or recovering the pre-coating solution from the dynamic membrane filter; and an air supply module for supplying air to the dynamic membrane filter. Gas is introduced into the filter to dry the inner wall of the filter and the dynamic membrane, and / or gas is introduced into the dynamic membrane filter to blow off the dried sludge cake on the dynamic membrane; wherein, the dynamic membrane filter includes a filter body and a dynamic membrane filter element disposed within the filter body; the dynamic membrane filter element includes a filter cloth skeleton and a filter cloth covering the filter cloth skeleton, the filter cloth dividing the space inside the dynamic membrane filter into a raw water chamber and a purified water temporary storage chamber; after the pre-coated solution is introduced into the raw water chamber, a dynamic membrane is formed on the outer surface of the filter cloth, fluoride in the fluoride-containing wastewater is intercepted by the dynamic membrane, and purified water passes through the dynamic membrane into the purified water temporary storage chamber and is then output to the purified water tank.

[0009] Furthermore, the water purification tank is connected to the water storage chamber inside the dynamic membrane filter via a water purification outlet pipe, and is used to receive the treated purified water.

[0010] Furthermore, the raw water tank is connected to the raw water chamber of the dynamic membrane filter via a raw water inlet pipe, for unidirectional input of fluoride-containing wastewater to be treated.

[0011] Furthermore, the raw water tank is connected to the raw water chamber of the dynamic membrane filter via a raw water outlet pipe for unidirectional recovery of fluoride-containing wastewater.

[0012] Furthermore, the pre-coated solution tank is connected to the raw water chamber of the dynamic membrane filter through a pre-coated inlet pipe for unidirectional input of the pre-coated solution, which enters the purified water temporary storage chamber after passing through the filter cloth.

[0013] Furthermore, the pre-coated solution tank is connected to the purified water storage chamber of the dynamic membrane filter through a pre-coated liquid outlet pipe for unidirectional recovery of the pre-coated solution.

[0014] Furthermore, the dynamic membrane filter is also provided with a pre-coating overflow pipe that is connected to the pre-coating solution tank.

[0015] Furthermore, the air supply module is connected to the raw water chamber through a forward blowing drying pipe, which is used to introduce high-pressure air to promote water evaporation and dry and dehydrate the trapped material on the surface of the dynamic membrane to form a dry mud cake.

[0016] Furthermore, the air supply module introduces high-pressure air into the purified water temporary storage chamber through the backflushing and shaking pipe to shake off the dried mud cake on the surface of the dynamic membrane.

[0017] Furthermore, the dynamic membrane filter is equipped with an exhaust pipe.

[0018] Furthermore, the dynamic membrane filter is provided with a discharge port at the bottom.

[0019] Furthermore, the dynamic membrane filter is equipped with an inlet pipe for introducing clean water or cleaning solution into the dynamic membrane filter for system cleaning.

[0020] Furthermore, the system cleaning includes both online cleaning and offline cleaning modes.

[0021] Specifically, in the online cleaning mode, tap water is introduced into the dynamic membrane filter through the inlet pipe and high-pressure gas is introduced through the air supply module. The backwashing of the dynamic membrane is completed through the flushing action of air and water.

[0022] Specifically, in offline cleaning mode, the dynamic membrane filter element is removed, cleaned, and then reinstalled to restore it to its initial state.

[0023] This invention also provides an operating method for a dynamic membrane filtration system for fluoride-containing wastewater treatment and resource recovery. The operating method includes the following stages: Pre-coating stage: A pre-coating solution is introduced into the dynamic membrane filter through a pre-coating solution tank to form a dynamic membrane on the filter cloth surface; the pre-coating stage ends when the pressure difference between the inside and outside of the dynamic membrane reaches the filtration operating conditions; Defluoridation stage: Fluoride-containing wastewater is introduced into the dynamic membrane filter through a raw water tank. Fluorides in the wastewater are trapped by the dynamic membrane and continuously enriched on the surface, and the pressure difference between the inside and outside of the membrane gradually increases; the defluoridation stage ends when the pressure difference reaches the design value; Drainage and drying stage: The fluoride-containing wastewater is drained, and high-pressure air is introduced into the dynamic membrane filter through an air supply module to promote water evaporation and dry the trapped material on the surface of the dynamic membrane to form a dry sludge cake; the pressure is released, and the drainage and drying stage ends; Blow-off and shaking stage: High-pressure air is introduced into the filter element of the dynamic membrane filter through an air supply module, and the dry sludge cake on the surface of the dynamic membrane is shaken off by high-speed gas and dynamic membrane vibration; the dry sludge cake is discharged, the blow-off and shaking stage ends, and the system returns to its initial state.

[0024] Furthermore, the pre-coating solution is a mixture of diatomaceous earth, coagulant aid, raw water, and coagulant.

[0025] Furthermore, the pressure difference between the inside and outside of the dynamic membrane ranges from 0.1 to 0.6 MPa.

[0026] Compared with the prior art, the present invention has the following technical advantages: (1) The dynamic membrane filtration system of the present invention is cleverly connected and configured with a raw water tank, a pre-coated solution tank, a filter, a purified water tank and an air supply module, so that after the pre-coated solution is input into the raw water chamber, a dynamic membrane is formed on the outer surface of the filter cloth. Fluorides in the fluoride-containing wastewater are intercepted by the dynamic membrane, and purified water is output to the purified water tank after passing through the dynamic membrane into the purified water storage chamber. The present invention can separate and purify fluorides in high-fluoride wastewater through a dynamic membrane filter, effectively improving the treatment effect of fluoride-containing wastewater and the recovery efficiency of fluorides, and reducing the investment and cost of the fluoride-containing wastewater treatment system.

[0027] (2) The dynamic membrane filtration system of the present invention innovatively integrates forward blowing to dry fluoride-containing sludge cake and reverse blowing to shake off the dried sludge cake through a multi-functional air supply module, so that the dynamic membrane can be restored to its initial state, which can significantly extend the service life of the filter cloth. It is especially suitable for industrial wastewater scenarios with high fluoride concentration and resource recovery needs, and has both technical feasibility and economic efficiency.

[0028] (3) The dried mud cake collected by this invention has a high fluorine content and can be used as a raw material for fluorine resource recovery, which is in line with the concept of circular economy.

[0029] (4) The dynamic membrane filtration system of the present invention integrates multiple functions such as pre-coating, filtration, drying and stripping, and the raw water tank, pre-coating solution tank, air supply module, etc. can be flexibly configured according to water volume and water quality to meet different scale treatment needs. Attached Figure Description

[0030] Figure 1 is a schematic diagram of the overall structure of the dynamic membrane filtration system of the present invention.

[0031] Figure 2 is a schematic diagram of the overall structure of the dynamic membrane filter of the present invention.

[0032] Figure 3 is a cross-sectional schematic diagram of the dynamic membrane filter of the present invention.

[0033] Figure 4 is a schematic diagram of the structure of the dynamic membrane filter of the present invention when it has two filter elements.

[0034] Figure 5 is a schematic diagram of the dynamic membrane filter of the present invention in the pre-coating stage.

[0035] Figure 6 is a schematic diagram of the dynamic membrane filter of the present invention during the defluorination stage.

[0036] Figure 7 is a schematic diagram of the dynamic membrane filter of the present invention during the drainage drying stage.

[0037] Figure 8 is a schematic diagram of the dynamic membrane filter of the present invention during the blow-off and shaking stage.

[0038] Figure 9 is a cross-sectional schematic diagram of the dynamic membrane filter of the present invention during the defluorination cycle.

[0039] Figure 10 is a schematic diagram of the online cleaning of the dynamic membrane filter of the present invention.

[0040] Figure 11 is a schematic diagram of the dynamic membrane filter of the present invention during offline cleaning.

[0041] The markings in the diagram are as follows: 1-Dynamic membrane filter, 1.1-Filter body, 1.2-Filter cloth skeleton, 1.3-Filter cloth, 2-Clean water tank, 3-Raw water tank, 4-Pre-coated solution tank, 5-Air supply module, 6-Clean water outlet pipe, 7-Raw water inlet pipe, 8-Raw water outlet pipe, 9-Pre-coated liquid inlet pipe, 10-Pre-coated liquid outlet pipe, 11-Pre-coated overflow pipe, 12-Forward blowing drying pipe, 13-Backblowing and shaking pipe, 14-Exhaust pipe, 15-Material outlet, 16-Liquid inlet pipe. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0043] In this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation 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; the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly, for example, they can be fixed connections, detachable connections, or integral connections; they can be mechanical connections or electrical connections; they can be direct connections or indirect connections through an intermediate medium; they can be internal connections between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0044] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0045] Example 1: This example provides a dynamic membrane filtration system for the treatment and resource recovery of fluoride-containing wastewater. As shown in Figure 1, the dynamic membrane filtration system specifically includes a dynamic membrane filter 1, a purified water tank 2, a raw water tank 3, a pre-coated solution tank 4, and an air supply module 5, which are connected through process pipelines.

[0046] As shown in Figures 2-4, the dynamic membrane filter 1 in this embodiment is the core separation and purification device used to treat fluoride-containing wastewater. The dynamic membrane filter 1 includes a filter body 1.1 and a dynamic membrane filter element disposed within the filter body 1.1. At least one dynamic membrane filter element is provided, and each dynamic membrane filter element includes a filter cloth frame 1.2 and a filter cloth 1.3 covering the filter cloth frame 1.2. The filter cloth 1.3 divides the space within the dynamic membrane filter 1 into a raw water chamber (i.e., outside the filter element) and a purified water temporary storage chamber (i.e., inside the filter element).

[0047] In this embodiment, the water purification tank 2 is connected to the dynamic membrane filter 1 and is used to store the treated fluoride-containing wastewater. One or more water purification tanks 2 can be installed, and the specific number can be determined based on the actual volume of water to be treated.

[0048] In this embodiment, the raw water tank 3 is used to input fluoride-containing wastewater into the dynamic membrane filter 1 and / or to recover fluoride-containing wastewater from the dynamic membrane filter 1. When there is only one raw water tank 3, one pipeline of the raw water tank 3 is connected to the dynamic membrane filter 1 for unidirectional input of fluoride-containing wastewater, and the other pipeline of the raw water tank 3 is connected to the dynamic membrane filter 1 for unidirectional recovery of fluoride-containing wastewater. When there are two or more raw water tanks 3, one or more of them are used for unidirectional input of fluoride-containing wastewater, and the remaining raw water tanks 3 are used for unidirectional recovery of fluoride-containing wastewater. The specific number of raw water tanks 3 can be determined according to the actual water volume to be treated.

[0049] In this embodiment, the pre-coating solution tank 4 is used to input the pre-coating solution into the dynamic membrane filter 1 and form a dynamic membrane on the filter cloth 1.3, and / or to recover excess pre-coating solution from the dynamic membrane filter 1. When there is only one pre-coating solution tank 4, one of the pipes of the pre-coating solution tank 4 is connected to the dynamic membrane filter 1 for unidirectional input of the pre-coating solution, and the other pipe is connected to the dynamic membrane filter 1 for unidirectional recovery of the pre-coating solution. When there are two or more pre-coating solution tanks 4, one or more of them are used for unidirectional input of the pre-coating solution, and the remaining tanks are used for unidirectional recovery of the pre-coating solution. The specific number of pre-coating solution tanks 4 can be determined according to the number of dynamic membrane filter elements and the relevant parameters of the dynamic membrane.

[0050] In this embodiment, the air supply module 5 is used to introduce gas into the dynamic membrane filter 1 to dry the inner wall of the filter and the dynamic membrane, and / or to introduce gas into the dynamic membrane filter 1 to blow off the dried sludge cake on the dynamic membrane. When there is only one air supply module 5, one of the pipelines of the air supply module 5 is connected to the dynamic membrane filter 1 and is used to unidirectionally introduce high-pressure air to dry the inner wall of the dynamic membrane filter 1 and the dynamic membrane; the other pipeline of the air supply module 5 is connected to the dynamic membrane filter 1 and is used to unidirectionally introduce high-pressure air to blow off the dried sludge cake on the dynamic membrane. When there are two or more air supply modules 5, one or more of them are used to unidirectionally introduce high-pressure air to dry the inner wall of the dynamic membrane filter 1 and the dynamic membrane, and the remaining air supply modules 5 are used to unidirectionally introduce high-pressure air to blow off the dried sludge cake on the dynamic membrane. The specific number of air supply modules 5 can be determined according to the actual working conditions.

[0051] The working principle of the dynamic membrane filtration system in this embodiment is briefly described as follows: After the pre-coated solution is introduced into the raw water chamber, a dynamic membrane is formed on the outer surface of the filter cloth 1.3. Fluorides in the fluoride-containing wastewater are retained by the dynamic membrane, and the purified water passes through the dynamic membrane into the purified water storage chamber and is then output to the purified water tank 2.

[0052] As shown in Figures 5-9, the operation method of the dynamic membrane filtration system in this embodiment specifically includes the following stages: Pre-coating stage: a pre-coating solution is introduced into the dynamic membrane filter 1 through the pre-coating solution tank 4 to form a dynamic membrane on the surface of the filter cloth 1.3; the pre-coating stage ends when the pressure difference between the inside and outside of the dynamic membrane reaches the filtration operating conditions.

[0053] Defluoridation stage: Fluorine-containing wastewater is introduced into the dynamic membrane filter 1 through the raw water tank 3. The fluoride in the wastewater is intercepted by the dynamic membrane and continuously enriched on the surface, and the pressure difference between the inside and outside of the membrane gradually increases. When the pressure difference between the inside and outside reaches the design value, the defluoridation stage ends.

[0054] Drainage and drying stage: Drain the fluoride-containing wastewater, introduce high-pressure air into the dynamic membrane filter 1 through the air supply module 5 to promote water evaporation, and dry and dehydrate the trapped material on the surface of the dynamic membrane to form a dry mud cake; release the pressure, and the drainage and drying stage ends.

[0055] Air removal and shaking stage: High-pressure air is introduced into the filter element of dynamic membrane filter 1 through air supply module 5. The dry mud cake on the surface of dynamic membrane is shaken off by high-speed gas and dynamic membrane vibration. The dry mud cake is discharged, the air removal and shaking stage ends, and the filter returns to the initial state.

[0056] Example 2: This example provides a dynamic membrane filtration system for the treatment and resource recovery of fluoride-containing wastewater. The dynamic membrane filtration system specifically includes a dynamic membrane filter 1, a purified water tank 2, a raw water tank 3, a pre-coated solution tank 4, and an air supply module 5, all connected via process piping.

[0057] Compared with Example 1, the process pipeline of this example specifically includes a clean water outlet pipe 6, a raw water inlet pipe 7, a raw water outlet pipe 8, a pre-coating liquid inlet pipe 9, a pre-coating liquid outlet pipe 10, a pre-coating overflow pipe 11, a forward blowing drying pipe 12, a reverse blowing and shaking pipe 13, an exhaust pipe 14, and a liquid inlet pipe 16.

[0058] Specifically, in this embodiment, the water purification tank 2 is connected to the water purification temporary storage chamber in the dynamic membrane filter 1 through the water purification outlet pipe 6, and is used to receive the treated water.

[0059] In this embodiment, the raw water tank 3 is connected to the raw water chamber of the dynamic membrane filter 1 through the raw water inlet pipe 7, and is used for unidirectional input of fluoride-containing wastewater to be treated.

[0060] In this embodiment, the raw water tank 3 is connected to the raw water chamber of the dynamic membrane filter 1 through the raw water outlet pipe 8, and is used for unidirectional recovery of fluoride-containing wastewater.

[0061] In this embodiment, the pre-coated solution tank 4 is connected to the raw water chamber of the dynamic membrane filter 1 through the pre-coated inlet pipe 9, and is used for unidirectional input of pre-coated solution. The pre-coated solution enters the purified water temporary storage chamber after passing through the filter cloth 1.3.

[0062] In this embodiment, the pre-coated solution tank 4 is connected to the purified water storage chamber of the dynamic membrane filter 1 via the pre-coated outlet pipe 10, for unidirectional recovery of the pre-coated solution. The dynamic membrane filter 1 is also provided with a pre-coated overflow pipe 11 connected to the pre-coated solution tank 4.

[0063] In this embodiment, the air supply module 5 is connected to the raw water chamber through the forward blowing drying pipe 12, and is used to introduce high-pressure air to promote water evaporation and dry and dehydrate the trapped material on the surface of the dynamic membrane to form a dry mud cake.

[0064] In this embodiment, the air supply module 5 introduces high-pressure air into the purified water storage chamber through the backflushing and shaking pipe 13 to shake off the dried mud cake on the surface of the dynamic membrane. The dynamic membrane filter 1 is equipped with an exhaust pipe 14.

[0065] In addition, the bottom of the dynamic membrane filter 1 in this embodiment is provided with a discharge port 15 for discharging the dried pre-coated liquid cake.

[0066] In addition, the dynamic membrane filter 1 in this embodiment is provided with an inlet pipe 16 for introducing clean water into the dynamic membrane filter 1 for system cleaning.

[0067] Specifically, the above-mentioned system cleaning includes two modes: online cleaning and offline cleaning.

[0068] As shown in Figure 10, in the online cleaning mode, tap water is introduced into the dynamic membrane filter 1 through the liquid inlet pipe 16 and high-pressure gas is introduced through the air supply module 5. The backwashing of the dynamic membrane is completed by the flushing action of air and water.

[0069] As shown in Figure 11, the offline cleaning mode removes the dynamic membrane filter cartridge for cleaning, and then restores it to its initial state after reinstallation.

[0070] Example 3: In view of the shortcomings of existing technologies, such as the inability to perform deep defluorination, the lack of sustainability of defluorination processes, and the inability to effectively recover the separated fluorine, this example provides a dynamic membrane filtration system and its operation method for the treatment and resource recovery of fluoride-containing wastewater.

[0071] The dynamic membrane filtration system in this embodiment specifically includes a dynamic membrane filter 1, a purified water tank 2, a raw water tank 3, a pre-coated solution tank 4, and an air supply module 5, which are connected through process pipelines. The process pipelines specifically include a purified water outlet pipe 6, a raw water inlet pipe 7, a raw water outlet pipe 8, a pre-coated solution inlet pipe 9, a pre-coated solution outlet pipe 10, a pre-coated overflow pipe 11, a forward-blowing drying pipe 12, a reverse-blowing and shaking pipe 13, an exhaust pipe 14, and a liquid inlet pipe 16.

[0072] The raw water tank 3 stores fluoride-containing wastewater that needs to be defluorinated, the pre-coating solution tank 4 stores pre-coating solvent, and the purified water tank 2 stores the treated fluoride-containing wastewater.

[0073] The air supply module 5 in this embodiment consists of an air compressor, an air tank, and an air pipeline, all of which are conventional industrial devices and are not specifically limited here.

[0074] The dynamic membrane filter 1 in this embodiment is the core purification equipment for separating fluorides. Specifically, it consists of a filter body 1.1 and filter elements (composed of a filter cloth skeleton 1.2 and a filter cloth 1.3). The number of elements can be adjusted according to the required water volume, and it is connected to the system in conjunction with the aforementioned process piping. The filter cloth 1.3 can be selected from conventional non-woven fabrics.

[0075] In this embodiment, all process pipelines use conventional pipelines from the wastewater treatment field. Valves and pumps can be configured on these pipelines and connected to a PLC control system for controlling each pipeline. The aforementioned pipelines, valves, and control systems are all conventionally used in industry, and those skilled in the art can configure them according to actual conditions; no specific limitations are made here.

[0076] A complete defluorination filtration cycle of the dynamic membrane filtration system in this embodiment consists of four stages: pre-coating stage, defluorination stage, drainage and drying stage, which are continuously cycled.

[0077] (1) Pre-coating stage: The pre-coating solution tank continuously feeds pre-coating solution into the dynamic membrane filter 1 through the pre-coating inlet pipe 9. After passing through the dynamic membrane filter 1, the pre-coating solution flows back to the pre-coating solution tank 4 through the pre-coating outlet pipe 10 and the pre-coating overflow pipe 11, forming a cycle. During the process of passing through the filter element, the pre-coating solution forms a dynamic membrane on the surface of the filter cloth 1.3. As the dynamic membrane forms, the effluent changes from cloudy to clear. After producing clear water, the pre-coating stage ends, and the pre-coating solution tank stops feeding pre-coating solution into the dynamic membrane filter 1.

[0078] (2) Defluoridation stage: Fluoride-containing wastewater is continuously fed into the dynamic membrane filter 1 through the raw water inlet pipe 7 from the raw water tank 3. The fluoride in the wastewater is intercepted by the dynamic membrane and continuously enriched on its surface. The filtered purified water enters the purified water tank 2 through the purified water outlet pipe 6, completing the process of fluoride separation and enrichment in the fluoride-containing wastewater. As the amount of fluoride intercepted on the surface of the dynamic membrane gradually increases, the pressure difference between the inside and outside of the membrane gradually increases. When the pressure difference reaches the design value, the defluoridation stage ends, and the raw water tank 3 stops feeding fluoride-containing wastewater into the dynamic membrane filter 1.

[0079] (3) Drainage and drying stage: Open the raw water outlet pipe 8 to release the fluoride-containing wastewater in the dynamic membrane filter 1. The air supply module 5 introduces high-pressure air into the dynamic membrane filter 1 through the forward blowing drying pipe 12. The high-pressure air passes through the dynamic membrane and filter element from the outside to the inside. The high-speed flowing gas evaporates the moisture in the filter and dries and dehydrates the residue on the surface of the dynamic membrane to form a dry sludge cake. After drying, open the exhaust pipe 14 to release the filter pressure, and the drainage and drying stage ends.

[0080] (4) Blow-off and shake-off stage: The air supply module 5 introduces high-pressure air into the filter element through the back-blowing and shake-off pipe 13. The high-pressure air passes through the filter element and dynamic membrane from the inside out. The high-speed gas and the dynamic membrane vibrate and shake off the mud cake on the surface of the dynamic membrane. The high-pressure gas carries the mud cake to the bottom of the filter body 1.1 and discharges it from the discharge port 15. The blow-off and shake-off stage ends and the filter returns to its initial state.

[0081] The cleaning of dynamic membrane systems is divided into online cleaning and offline cleaning (once every 3-6 months).

[0082] The online cleaning process is as follows: After each operating cycle, clean water (usually tap water) is introduced into the dynamic membrane filter 1 through the inlet pipe 16, and high-pressure air is introduced into the filter element through the backflushing and shaking pipe 13. The high-pressure air passes through the filter element and dynamic membrane from the inside out, and the online cleaning of the dynamic membrane filter 1 is completed by the flushing action of air and water on the dynamic membrane. After cleaning, the dynamic membrane filter 1 returns to its initial state.

[0083] The offline cleaning process is as follows: the filter element is removed from the dynamic membrane filter 1, soaked and cleaned in a special cleaning agent, and then reinstalled into the dynamic membrane filter 1, restoring the dynamic membrane filter 1 to its initial state.

[0084] The dynamic membrane filtration system of this embodiment can separate fluoride from raw water into purified water and enrich the fluoride to form a dried sludge cake, thus completing the diversion, purification, and effective recovery of fluoride in fluoride-containing wastewater. Specific industrial application examples are given below.

[0085] Example: In this example, the fluoride-containing wastewater originates from a chip manufacturing company, with fluoride concentrations ranging from 200 to 500 mg / L. - The testing standard is ion-selective electrode method, and the filter cloth used is made of non-woven fabric with a pore size of 100 μm.

[0086] Pre-coating stage: The pre-coating solution is prepared by mixing diatomaceous earth, coagulant aid, coagulant and raw water in a ratio of 10:1:5:1000; then the pre-coating solution is passed through a filter for circulation and filtration for 20 minutes.

[0087] Defluoridation stage: Add appropriate amounts of sulfuric acid and calcium chloride to the fluoride-containing wastewater, react and coagulate for 15 minutes, then pass it into the filter. During the filtration process, fluoride precipitates and accumulates on the surface of the filter cloth until the pressure difference between the inside and outside of the dynamic membrane reaches 0.35 MPa.

[0088] The concentration of fluoride compounds in the effluent is no higher than 5 mg / L, meeting the direct discharge requirements of the "Electronic Industry Water Pollutant Discharge Standard" GB39731-2020. Meanwhile, the fluoride-containing sludge cake contains more than 50% fluoride compounds and has a water content of no more than 50%, eliminating the need for further dehydration and volume reduction. It can be used as a flux or slag-reducing agent in steel smelting.

[0089] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A dynamic membrane filtration system for fluoride-containing wastewater treatment and resource recovery, characterized in that, The dynamic membrane filtration system includes: a dynamic membrane filter (1) for treating fluoride-containing wastewater; a purification tank (2) for storing the treated fluoride-containing wastewater; a raw water tank (3) for feeding fluoride-containing wastewater into the dynamic membrane filter (1) and / or recovering fluoride-containing wastewater from the dynamic membrane filter (1); a pre-coating solution tank (4) for feeding a pre-coating solution into the dynamic membrane filter (1) to form a dynamic membrane and / or recovering the pre-coating solution from the dynamic membrane filter (1); and an air supply module (5) for introducing gas into the dynamic membrane filter (1) to dry the filter inner wall and the dynamic membrane, and / or for introducing gas into the dynamic membrane filter (1). Gas is used to blow off the dry mud cake on the dynamic membrane; wherein, the dynamic membrane filter (1) includes a filter body (1.1) and a dynamic membrane filter element disposed in the filter body (1.1); the dynamic membrane filter element includes a filter cloth skeleton (1.2) and a filter cloth (1.3) covering the filter cloth skeleton (1.2), the filter cloth (1.3) divides the space inside the dynamic membrane filter (1) into a raw water chamber and a purified water temporary storage chamber; after the pre-coated solution is introduced into the raw water chamber, a dynamic membrane is formed on the outer surface of the filter cloth (1.3), the fluoride in the fluoride-containing wastewater is intercepted by the dynamic membrane, and the purified water enters the purified water temporary storage chamber through the dynamic membrane and is then output to the purified water tank (2).

2. The dynamic membrane filtration system for fluoride-containing wastewater treatment and resource recovery according to claim 1, characterized in that, The water purification tank (2) is connected to the water purification temporary storage chamber in the dynamic membrane filter (1) through the water purification outlet pipe (6) and is used to receive the treated water.

3. The dynamic membrane filtration system for fluoride-containing wastewater treatment and resource recovery according to claim 1, characterized in that, The raw water tank (3) is connected to the raw water chamber of the dynamic membrane filter (1) through the raw water inlet pipe (7) for unidirectional input of fluoride-containing wastewater to be treated; the raw water tank (3) is connected to the raw water chamber of the dynamic membrane filter (1) through the raw water outlet pipe (8) for unidirectional recovery of fluoride-containing wastewater.

4. The dynamic membrane filtration system for fluoride-containing wastewater treatment and resource recovery according to claim 1, characterized in that, The pre-coated solution tank (4) is connected to the raw water chamber of the dynamic membrane filter (1) through the pre-coated inlet pipe (9) for unidirectional input of pre-coated solution. The pre-coated solution enters the purified water storage chamber after passing through the filter cloth (1.3). The pre-coated solution tank (4) is connected to the purified water storage chamber of the dynamic membrane filter (1) through the pre-coated outlet pipe (10) for unidirectional recovery of pre-coated solution. The dynamic membrane filter (1) is also provided with a pre-coated overflow pipe (11) connected to the pre-coated solution tank (4).

5. A dynamic membrane filtration system for fluoride-containing wastewater treatment and resource recovery according to claim 1, characterized in that, The air supply module (5) is connected to the raw water chamber through the forward blowing drying pipe (12) to introduce high-pressure air to promote water evaporation and dry the residue on the surface of the dynamic membrane to form a dry mud cake; the air supply module (5) introduces high-pressure air into the purified water temporary storage chamber through the back-blowing shaking pipe (13) to shake off the dry mud cake on the surface of the dynamic membrane; the dynamic membrane filter (1) is provided with an exhaust pipe (14).

6. A dynamic membrane filtration system for fluoride-containing wastewater treatment and resource recovery according to claim 1, characterized in that, The dynamic membrane filter (1) is provided with a discharge port (15) at the bottom.

7. A dynamic membrane filtration system for fluoride-containing wastewater treatment and resource recovery according to claim 1, characterized in that, The dynamic membrane filter (1) is provided with an inlet pipe (16) for introducing clean water or cleaning solution into the dynamic membrane filter (1) for system cleaning.

8. A dynamic membrane filtration system for fluoride-containing wastewater treatment and resource recovery according to claim 7, characterized in that, The system cleaning includes two modes: online cleaning and offline cleaning. In the online cleaning mode, tap water is introduced into the dynamic membrane filter (1) through the liquid inlet pipe (16) and high-pressure gas is introduced through the gas supply module (5). The backwashing of the dynamic membrane is completed by the flushing action of gas and water. In the offline cleaning mode, the dynamic membrane filter element is removed and cleaned, and then reinstalled to restore it to its initial state.

9. A method for operating a dynamic membrane filtration system for fluoride-containing wastewater treatment and resource recovery as described in any one of claims 1-8, characterized in that, The operation method includes the following stages: Pre-coating stage: Pre-coating solution is introduced into the dynamic membrane filter (1) through the pre-coating solution tank (4) to form a dynamic membrane on the surface of the filter cloth (1.3); The pre-coating stage ends when the pressure difference between the inside and outside of the dynamic membrane reaches the filtration operating condition requirements. Defluoridation stage: Fluorine-containing wastewater is introduced into the dynamic membrane filter (1) through the raw water tank (3). The fluoride in the wastewater is intercepted by the dynamic membrane and continuously enriched on the surface, and the pressure difference between the inside and outside of the membrane gradually increases. When the pressure difference between the inside and outside reaches the design value, the defluoridation stage ends. Drainage and drying stage: The fluorine-containing wastewater is drained, and high-pressure air is introduced into the dynamic membrane filter (1) through the air supply module (5) to promote water evaporation and dry the intercepted material on the surface of the dynamic membrane to form a dry sludge cake. The pressure is released, and the drainage and drying stage ends. Blow-off and shaking stage: High-pressure air is introduced into the filter element of the dynamic membrane filter (1) through the air supply module (5), and the dry sludge cake on the surface of the dynamic membrane is shaken off by high-speed gas and dynamic membrane vibration. The dry sludge cake is discharged, the blow-off and shaking stage ends, and the system returns to the initial state.

10. The operating method of the dynamic membrane filtration system for fluoride-containing wastewater treatment and resource recovery according to claim 9, characterized in that, The pre-coating solution is a mixture of diatomaceous earth, coagulant aid, raw water and coagulant; the pressure difference between the inside and outside of the dynamic membrane is in the range of 0.1~0.6 MPa.

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