A ferric phosphate wastewater treatment system and treatment method

Abstract

This invention discloses a ferric phosphate wastewater treatment system and method, belonging to the field of wastewater treatment technology. The treatment system includes a circulating thickening facility and a tubular microfiltration membrane module. The sludge discharge port of the circulating thickening facility is connected to a filter press via a sludge pump, and the effluent port of the circulating thickening facility is connected to a regulating pipe for adjusting water flow via a circulating pump. The regulating pipe is equipped with a detachable inner tube assembly and a detachable filter screen assembly. The regulating pipe is connected to the inlet pipe of the tubular microfiltration membrane module. A tubular microfiltration membrane permeate tank and a reverse osmosis membrane module are sequentially connected after the tubular microfiltration membrane module. The reverse osmosis membrane module is connected to an evaporator and the reverse osmosis membrane permeate tank, respectively. The reverse osmosis membrane permeate tank is connected to a recycled water tank, and the reverse osmosis membrane permeate tank is connected to the tubular microfiltration membrane permeate tank via a return pipe. Furthermore, this invention also relates to a treatment method using the above-mentioned ferric phosphate wastewater treatment system.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular, to a ferric phosphate wastewater treatment system. Furthermore, this invention also relates to a method for treating ferric phosphate wastewater using the aforementioned ferric phosphate wastewater treatment system. Background Technology

[0002] Because of its lower cobalt content, lithium batteries are more expensive, followed by nickel and manganese, while iron is the cheapest. Therefore, lithium batteries made with lithium iron phosphate cathode material are the cheapest. Another advantage is that they are cleaner than ternary lithium batteries.

[0003] The production of ferric phosphate involves processes such as synthesis, washing, aging, and evaporation drying. Different production processes and raw material sources result in different ferric phosphate production methods; currently, the mainstream processes are the ammonium process and the sodium process. Regardless of the process used, a large amount of ferric phosphate mother liquor and washing wastewater or combined wastewater (wash water and mother liquor are mixed and discharged) are generated. The composition of the wastewater varies and is complex. The main pollutants are phosphate, sulfate, ammonium (sodium ions in sodium process wastewater), fluoride ions, and heavy metal ions (calcium, magnesium, iron, manganese, silicon, zinc, nickel, etc.). The wastewater generated during the production of ferric phosphate includes wash water and mother liquor. The mother liquor is acidic wastewater containing a large amount of high concentrations of ammonium ions (sodium ions in the sodium process wastewater), sulfate ions, phosphate ions (salts), heavy metal ions, and inorganic salts. The wash water also contains some ammonium ions (sodium ions in the sodium process wastewater), sulfate ions, phosphate ions (salts), etc. In addition to its complex composition, the above wastewater has a significant characteristic of high TDS. The TDS of the mother liquor can reach 50,000-60,000 mg / L, and the TDS of the wash water wastewater can reach 5,000-10,000 mg / L.

[0004] Currently, common pretreatment methods for ferric phosphate wastewater, such as chemical dosing, MAP and stripping, and sedimentation and filtration, have the following drawbacks:

[0005] 1) It is necessary to add ammonia, PAM, defluorinating agents and other agents. Among them, PAM will cause fouling in the reverse osmosis concentration and reuse system and is not easy to clean. At the same time, it increases the amount of sludge and increases the cost of secondary treatment.

[0006] 2) A large sedimentation tank is required for solid-liquid separation, which requires a large area and significant civil engineering investment.

[0007] 3) The filter requires frequent backwashing, which consumes a lot of recycled water. The filter media needs to be replaced regularly, and the replaced filter media needs to be treated twice.

[0008] 4) The UF system requires a large investment, needs regular backwashing, and consumes a large amount of recycled water and chemicals;

[0009] 5) Chemical dosing method: More chemicals are added, resulting in a large amount of sludge and high secondary treatment costs;

[0010] 6) MAP and stripping method: This method requires a large amount of magnesium salts and steam. Although the by-products have some value, the wastewater treatment cost is high, and it is difficult to meet the standards for ammonia nitrogen and phosphate.

[0011] 7) Sedimentation and filtration method: The pretreatment process is complex, the investment cost is high, and the operation and maintenance are complicated.

[0012] In addition, during the treatment of ferric phosphate wastewater, the sludge concentration in the thickening facility is directly related to the subsequent wastewater treatment effect, and the sludge concentration is difficult to control; the flow rate of the inlet pipe of the wastewater treatment system is not adjustable, and when the wastewater flow rate is low, the large-diameter pipes waste electricity in lifting the wastewater; the large-area filter components inside the pipes are costly, difficult to disassemble, and easily damaged during disassembly and cleaning; in addition, the inner wall of the pipes needs to be cleaned frequently, which leads to frequent shutdowns and affects the wastewater treatment efficiency. Summary of the Invention

[0013] The purpose of this invention is to address the above-mentioned problems by providing a ferric phosphate wastewater treatment system and method, which provides targeted solutions to various problems in traditional processes and issues in the treatment system such as sludge concentration control, pipeline flow control, pipeline inner wall cleaning, and filter assembly disassembly.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0015] A ferric phosphate wastewater treatment system includes a circulation facility and a tubular microfiltration membrane module. The sludge discharge port of the circulation thickening facility is connected to a filter press via a sludge pump, and the effluent port of the circulation thickening facility is connected to a regulating pipe for adjusting water flow via a circulation pump. The regulating pipe is equipped with a detachable inner tube assembly and a detachable filter screen assembly. The regulating pipe is connected to the inlet pipe of the tubular microfiltration membrane module. A tubular microfiltration membrane permeate tank and a reverse osmosis membrane module are sequentially connected after the tubular microfiltration membrane module. The reverse osmosis membrane module is connected to an evaporator and the reverse osmosis membrane permeate tank, respectively. The reverse osmosis membrane permeate tank is connected to a recycled water tank, and the reverse osmosis membrane permeate tank is connected to the tubular microfiltration membrane permeate tank via a return pipe.

[0016] Furthermore, the regulating pipe includes an outer pipe, an inner pipe assembly is provided inside the outer pipe, the inner pipe assembly includes an inner pipe, a spacer cavity is provided between the outer pipe and the inner pipe, an elastic splice is provided on the wall of the inner pipe, and an regulating component is provided on the wall of the outer pipe. The regulating component is used to squeeze or stretch the elastic splice to adjust the diameter of the inner pipe. The two ends of the inner pipe are connected to the outer pipe through sealing elements, and the sealing elements are used to seal the spacer cavity between the inner pipe and the outer pipe.

[0017] Furthermore, the inner tube includes multiple arc-shaped tube walls, and adjacent arc-shaped tube walls are spliced ​​together by elastic splicing parts; the sealing element includes multiple elastic sealing strips and elastic connecting parts disposed between adjacent elastic sealing strips, the elastic sealing strips and the arc-shaped tube walls are arranged in a one-to-one correspondence, and the elastic connecting parts are used to be driven to be squeezed or stretched synchronously with the elastic splicing parts when adjusting the diameter of the inner tube.

[0018] Furthermore, the adjusting assembly includes an adjusting plate that penetrates the outer tube wall. The first end of the adjusting plate is connected to the inner tube wall, and the second end of the adjusting plate is located outside the outer tube and is provided with a mounting plate. The mounting plate is provided with a screw hole, and a bearing is provided on the outer tube wall. The adjusting assembly also includes an adjusting rod that is connected to the bearing and axially fixed relative to the bearing. The adjusting rod is a lead screw, and the adjusting rod passes through the screw hole and is threadedly connected to the screw hole.

[0019] Furthermore, the filter assembly includes a filter screen located at one end of the inner tube. The filter screen is mounted on the outer tube via a limiting component symmetrically arranged radially along the filter screen. The limiting component includes a first vertical plate and a second vertical plate arranged in parallel. Both the first and second vertical plates penetrate the outer tube wall, and their ends located outside the outer tube wall are connected by a top plate. The end of the first vertical plate located inside the outer tube is connected to the inner tube. The other end of the first vertical plate is provided with a mounting plate, which has a screw hole for threaded connection with an adjusting rod of a screw structure. A bearing is provided on the outer tube wall, and the bottom of the adjusting rod is connected to the bearing. The filter screen is located between the first vertical plate and the second vertical plate.

[0020] Furthermore, the filter screen is connected to the top plate by a spring, the cross-sectional length of the second vertical plate is longer than that of the first vertical plate, and a support part is provided on the second vertical plate to support the side of the filter screen. A conical tube-shaped guide part is provided at the tail end of the support part.

[0021] In addition, the present invention also discloses a treatment method using the above-mentioned iron phosphate wastewater treatment system, comprising the following steps:

[0022] S100. Pretreatment: The iron phosphate wastewater is pretreated using a tubular microfiltration membrane system, which includes a circulating concentration facility and a tubular microfiltration membrane module.

[0023] S101. Ferric phosphate wastewater first enters the circulating concentration facility for preliminary filtration.

[0024] S102. Wastewater from the circulating concentration facility enters the tubular microfiltration membrane module for microfiltration treatment.

[0025] S200, Reverse Osmosis Membrane Concentration and Reuse:

[0026] S201. The product water from the tubular microfiltration membrane module is pumped to the reverse osmosis membrane module for reverse osmosis filtration treatment.

[0027] S202. The permeate from the reverse osmosis membrane module is treated by the pure water system and then enters the recycled water tank, while the concentrate from the reverse osmosis membrane module enters the evaporation and crystallization system.

[0028] S300, Evaporation and Crystallization:

[0029] S301. The concentrate from the reverse osmosis membrane module is evaporated and concentrated using an evaporator to produce crystalline salt and condensate. The condensate is then transported back to the reverse osmosis membrane module for treatment to meet standards before being reused.

[0030] Furthermore, in the circulating concentration facility, coagulant, defluorinating agent, ammonia (for ammonium process wastewater) or sodium hydroxide (for sodium process wastewater) are added to form a mixed liquid. The mixed liquid enters the tubular microfiltration membrane module through a circulating pump. The mixed liquid achieves solid-liquid separation through the tubular microfiltration membrane module, and the product water enters the reverse osmosis membrane module while the concentrate is returned to the circulating concentration facility through a circulating pump. The sludge generated in the circulating concentration facility in step S101 is discharged and then subjected to pressure filtration to produce solid by-products.

[0031] Furthermore, the tubular microfiltration membrane module adopts a multi-module arrangement. The circulating concentration facility is equipped with a level gauge, a sludge concentration meter, and a pH meter. The number of working modules of the tubular microfiltration membrane module is adjusted according to the changing trends of the level gauge and the sludge concentration meter. When both the level gauge and the sludge concentration meter decrease, the number of working modules is reduced. When both the level gauge and the sludge concentration meter increase, the number of working modules is increased. When the level gauge decreases and the sludge concentration meter increases, the number of working modules is reduced. When the level gauge increases and the sludge concentration meter decreases, the number of working modules is increased.

[0032] Furthermore, the ferric phosphate wastewater includes wash water and mother liquor or a mixture of wash water and mother liquor, and the evaporator in the evaporation crystallization step is a triple-effect evaporator, MVR, or a combination of multi-effect and freeze crystallization evaporator.

[0033] The beneficial effects of this invention are:

[0034] 1. The "tubular microfiltration membrane system" is used to replace the traditional "coagulation sedimentation + filter + ultrafiltration membrane system". The installation requirements of the tubular microfiltration membrane are similar to those of the ultrafiltration membrane system, saving the civil engineering cost and investment of the sedimentation tank, while also saving the investment and installation space of the filter.

[0035] 2. This invention requires only one power lift from the equalization tank to the reverse osmosis membrane concentration raw water tank, solving the problem of high energy consumption from multiple power lifts in traditional processes (the traditional method uses a coagulation + sedimentation + filter + ultrafiltration membrane system to provide pretreatment for reverse osmosis membrane concentration, requiring four power lifts from the equalization tank to the coagulation and sedimentation tank, the sedimentation tank to the filter, the filter to the ultrafiltration membrane system, and the ultrafiltration membrane system to the reverse osmosis membrane concentration raw water tank). The specific design is as follows:

[0036] The tubular microfiltration membrane system adopts a circulating concentration facility + tubular microfiltration membrane module. By designing the residence time of wastewater in the circulating concentration facility, due to the high-flux circulation effect of the tubular microfiltration membrane system, the water quantity and quality can be homogenized quickly, eliminating the need for an equalization tank and reducing the need for upgrading from the equalization tank to subsequent systems.

[0037] The permeate from the tubular microfiltration membrane can be directly fed into the raw water tank of the reverse osmosis concentration system. This eliminates the need for coagulation and sedimentation systems, filters, and ultrafiltration membrane systems, while also reducing the need for booster systems in each system.

[0038] The tubular microfiltration membrane system only requires a circulation pump to circulate the concentration facility and the tubular microfiltration module. Solid-liquid separation is achieved during the water circulation process. From the time the raw water enters the circulation tank to the time it enters the raw water tank of the reverse osmosis concentration membrane system, the entire process only requires a matching circulation water pump to achieve a single power boost.

[0039] 3. This invention improves the permeate recovery rate of the pretreatment system. In traditional methods, the filter and UF system need to be cleaned separately and periodically, which consumes a large amount of reclaimed water (cleaning water accounts for about 6% of the system's treatment capacity). At the same time, cleaning causes process discontinuity and affects process operating efficiency. However, the tubular microfiltration membrane module of this invention adopts a multi-module design, and cleaning can be carried out in groups. Single groups or multiple groups can be cleaned simultaneously, reducing the impact on system operation.

[0040] 4. This invention optimizes the electrical control unit. In traditional processes, each ultrafiltration membrane system requires at least 7 pneumatic (electric) valves, 3 pressure transmitters (or pressure gauges), and a corresponding electrical control system. However, the tubular microfiltration membrane system in this invention only requires 3 pneumatic (electric) valves, 1 pressure transmitter (or pressure gauge), and a corresponding electrical control system per system, significantly reducing the number of electrical control points and consequently lowering operating and maintenance costs.

[0041] 5. The method of this invention uses a tubular microfiltration membrane system without the need to add PAM. Adding PAM itself incurs costs, and all added PAM will generate secondary treatment costs (sludge). This method can reduce sludge by 30%, and the effluent can directly enter the RO (reverse osmosis) system. The effluent does not contain PAM, microorganisms, or SS (suspended solids), and the effluent SDI is less than 3, which protects the RO membrane and extends its service life.

[0042] 6. This invention can achieve separate control of sludge concentration and retention time. If it is necessary to increase the sludge concentration, it can be controlled by producing water through the membrane system without discharging sludge. If it is necessary to reduce the sludge concentration, it can be achieved by combining sludge discharge and water production.

[0043] 7. The treatment method of the present invention can be used separately for the treatment of washing wastewater and mother liquor wastewater, and can also be applied to the treatment of mixed wastewater (washing water and mother liquor mixed and combined).

[0044] 8. The treatment system of this invention has an adjustment pipe at the front end of the tubular microfiltration membrane module. The inner tube of the adjustment pipe is detachable and has a spliced ​​structure design. The diameter of the inner tube can be adjusted by adjusting the component, thereby changing the flow rate of the adjustment pipe to adapt to the treatment needs of different working conditions and avoid wasting electricity. At the same time, the detachable design of the inner tube makes it easy to remove for cleaning or replacement without stopping the machine. In addition, the filter screen component inside the adjustment pipe is detachable, which facilitates the replacement or cleaning of large-area filter components. All of these can effectively improve the wastewater treatment efficiency.

[0045] Of course, any product implementing this invention does not necessarily need to achieve all the advantages described above simultaneously. In addition to the objectives, features, and advantages described above, this invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0046] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0047] Figure 1 This is an overall schematic diagram of the wastewater treatment method of the present invention.

[0048] Figure 2 This is a schematic diagram of the processing technology in Embodiment 1 of the present invention.

[0049] Figure 3 This is a schematic diagram of the processing technology in Embodiment 2 of the present invention.

[0050] Figure 4 This is a partial schematic diagram of a wastewater treatment system according to a preferred embodiment of the present invention.

[0051] Figure 5 This is a schematic diagram of the regulating pipe according to a preferred embodiment of the present invention.

[0052] Figure 6 This is a schematic diagram of the structure of the adjustment component according to a preferred embodiment of the present invention.

[0053] Figure 7 This is a schematic diagram of the installation structure of the inner tube according to a preferred embodiment of the present invention.

[0054] Figure 8 This is a schematic diagram of the installation structure of the filter screen according to a preferred embodiment of the present invention.

[0055] Figure 9 This is a schematic diagram of the limiting component according to a preferred embodiment of the present invention.

[0056] Legend: 1. Tubular microfiltration membrane module; 2. Adjustment pipe; 3. Circulation pump; 4. Sludge pump; 5. Outer pipe; 6. Adjustment rod; 7. Adjustment plate; 8. Mounting plate; 9. Flexible splicing part; 10. Flexible connection part; 11. Seal; 12. Inner pipe; 13. Spacing chamber; 14. Limiting component; 15. Filter screen; 16. Inlet pipe; 17. First vertical plate; 18. Top plate; 19. Spring; 20. Sealing platform; 21. Second vertical plate; 22. Support part; 23. Flow guide part. Detailed Implementation

[0057] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0058] Please refer to Figures 4-9 This invention discloses a ferric phosphate wastewater treatment system, including a circulating thickening facility and a tubular microfiltration membrane module 1. The sludge discharge port of the circulating thickening facility (such as a circulating thickening tank) is connected to a filter press via a sludge pump 4. The outlet of the circulating thickening facility is connected to a regulating pipe 2 for regulating water flow via a circulating pump 3. The regulating pipe 2 is equipped with a detachable inner tube assembly and a detachable filter screen assembly. The regulating pipe 2 is connected to the inlet pipe 16 of the tubular microfiltration membrane module 1. The tubular microfiltration membrane module 1 is followed by a tubular microfiltration membrane permeate tank and a reverse osmosis membrane module. The reverse osmosis membrane module is connected to an evaporator and a reverse osmosis membrane permeate tank, respectively. The reverse osmosis membrane permeate tank is followed by a recycled water tank, and the reverse osmosis membrane permeate tank is connected to the tubular microfiltration membrane permeate tank via a return pipe.

[0059] Specifically, an adjustment pipe 2 is provided at the front end of the tubular microfiltration membrane module 1. The inner tube 12 of the adjustment pipe 2 is detachable and has a splicing structure design. The diameter of the inner tube 12 can be adjusted by adjusting the adjustment component, thereby changing the flow rate of the adjustment pipe to adapt to the treatment needs of different working conditions and avoid wasting electricity. At the same time, the detachable design of the inner tube 12 makes it easy to remove for cleaning or replacement without stopping the machine. In addition, the filter screen component inside the adjustment pipe 2 is detachable, which facilitates the replacement or cleaning of large-area filter components, all of which can effectively improve the wastewater treatment efficiency.

[0060] For preferred options, please refer to [the provided text]. Figure 5 , 6 As shown in Figure 7, the regulating pipe 2 includes an outer pipe 5, and an inner pipe assembly is provided inside the outer pipe 5. The inner pipe assembly includes an inner pipe 12. There is a spacer cavity 13 between the outer pipe 5 and the inner pipe 12. An elastic splice part 9 is provided on the pipe wall of the inner pipe 12. An regulating component is provided on the pipe wall of the outer pipe 5. The regulating component is used to squeeze or stretch the elastic splice part 9 to adjust the diameter of the inner pipe 12. The two ends of the inner pipe 12 are connected to the outer pipe 5 through sealing members 11. The sealing members 11 are used to seal the spacer cavity 13 between the inner pipe 12 and the outer pipe 5.

[0061] In this embodiment, the inner tube 12 includes multiple arc-shaped tube walls, and adjacent arc-shaped tube walls are spliced ​​together by an elastic splicing part 9. The sealing element 11 includes multiple elastic sealing strips and an elastic connecting part 10 disposed between adjacent elastic sealing strips. The elastic sealing strips and the arc-shaped tube walls are arranged in a one-to-one correspondence. The elastic connecting part 10 is used to be driven to be squeezed or stretched synchronously with the elastic splicing part 9 when adjusting the diameter of the inner tube 12. The adjusting assembly includes an adjusting plate 7 penetrating the tube wall of the outer tube 5. The first end of the adjusting plate 7 is connected to the tube wall of the inner tube 12, and the second end of the adjusting plate 7 is located outside the outer tube 5 and is provided with a mounting plate 8. The mounting plate 8 is provided with a screw hole. The tube wall of the outer tube 5 is provided with a bearing. The adjusting assembly also includes an adjusting rod 6 connected to the bearing and axially fixed relative to the bearing. The adjusting rod 6 is a lead screw, and the adjusting rod 6 passes through the screw hole and is threadedly connected to the screw hole.

[0062] Understandably, since the elastic splicing part 9 of the inner tube 12 is an elastic element (such as an elastic soft plate, corrugated soft sheet, etc.), it can be folded or extended, thereby realizing the adjustable diameter of the inner tube 12. The two ends of the inner tube 12 are connected to the outer tube 5 through the sealing element 11 (also an elastic element of the splicing structure, which can be folded or extended synchronously with the inner tube 12; the sealing element 11 can be installed by bolts with the threaded holes on the inner tube 12 and the outer tube 5) to play a sealing role, preventing wastewater from entering the partition cavity 13 and ensuring that wastewater only flows through the inner tube 12.

[0063] When it is necessary to adjust the diameter of the inner tube 12, the adjusting plate 7 is raised or lowered by turning the adjusting rod 6. Since the lower end of the adjusting plate 7 is connected to the inner tube 12, the inner tube 12 wall can be raised or lowered simultaneously, thereby realizing the adjustment of the overall diameter of the inner tube 12.

[0064] Meanwhile, the inner tube 12 is designed to be detachable. When it is necessary to remove the inner tube 12, simply loosen the mounting bolts of the seal 11 to easily remove the seal 11 and the inner tube 12.

[0065] For preferred options, please refer to [the provided text]. Figure 8 , 9 As shown, the filter assembly includes a filter screen 15, which is located at one end of the inner tube 12. The filter screen 15 is mounted on the outer tube 5 via a limiting component 14 symmetrically arranged radially along the filter screen 15. The limiting component 14 includes a first vertical plate 17 and a second vertical plate 21 arranged in parallel. Both the first vertical plate 17 and the second vertical plate 21 penetrate the wall of the outer tube 5, and their ends located outside the wall of the outer tube 5 are connected by a top plate 18. The end of the first vertical plate 17 located inside the outer tube 5 is connected to the inner tube 12. The other end of the first vertical plate 17 is provided with a mounting plate 8, which has a screw hole for threaded connection with the adjusting rod 6 of the screw structure. The outer tube 5 has a bearing on its wall, and the bottom of the adjusting rod 6 is connected to the bearing. The filter screen 15 is located between the first vertical plate 17 and the second vertical plate 21.

[0066] It is understandable that the limiting component 14 has a frame-like structure to limit the installation of the filter screen 15. The limiting component 14 is located at the outer end of the inner tube 12, preferably at the inlet port 16 of the tubular microfiltration membrane module 1. A sealing platform 20 can be provided on the end face of the inlet port 16 to cooperate with the sealing ring to achieve a sealing installation. The first vertical plate 17 and the second vertical plate 21 of the limiting component 14, together with the top plate 18, form a limiting frame to install the filter screen 15. The outer end of the filter screen 15 is connected to the top plate 18 by a spring 19, so that the filter screen 15 has a certain amount of room to move within the limiting frame, which plays a role in buffering and protecting the filter screen 15. When the rigid connection of the wall is subjected to a large amount of water impact, the filter screen 15 has no displacement margin in all directions and is prone to large deformation.

[0067] In this embodiment, the filter screen 15 is connected to the top plate 18 by a spring 19. The cross-sectional length of the second vertical plate 21 is longer than that of the first vertical plate 17. A support part 22 is provided on the second vertical plate 21 to support the side of the filter screen 15. A conical cylindrical guide part 23 is provided at the tail end of the support part 22. The guide part 23 can reduce the impact of turbulence on the filter screen 15.

[0068] The height of the first vertical plate 17 can also be adjusted via the adjusting rod 6. When the diameter of the inner pipe 12 changes, the water flow rate changes. The lifting and lowering of the first vertical plate 17 drives the lifting and lowering of the second vertical plate 21, thereby adjusting the working area of ​​the filter screen 15. Because the second vertical plate 21 is relatively long and is equipped with a support part 22, it can simultaneously support and protect the side of the filter screen 15 and adjust the working area of ​​the filter screen 15.

[0069] In addition, the present invention also discloses a treatment method using the above-mentioned iron phosphate wastewater treatment system, comprising the following steps:

[0070] S100, Pretreatment: The iron phosphate wastewater is pretreated using a tubular microfiltration membrane system, which includes a circulating concentration facility (such as a circulating concentration tank) and a tubular microfiltration membrane module 1; S101, The iron phosphate wastewater first enters the circulating concentration facility for preliminary filtration; After the sludge generated in the circulating concentration facility is discharged, it is pressure filtered to produce solid by-products.

[0071] S102. Wastewater from the circulating concentration facility enters the tubular microfiltration membrane module 1 for microfiltration treatment.

[0072] S200, Reverse Osmosis Membrane Concentration and Reuse:

[0073] S201. The product water of the tubular microfiltration membrane module 1 is pumped to the reverse osmosis membrane module for reverse osmosis filtration treatment.

[0074] S202. The permeate from the reverse osmosis membrane module is treated by the pure water system and then enters the recycled water tank, while the concentrate from the reverse osmosis membrane module enters the evaporation and crystallization system.

[0075] S300, Evaporation and Crystallization:

[0076] S301. The concentrate from the reverse osmosis membrane module is evaporated and concentrated using an evaporator to produce crystalline salt and condensate. The condensate is then transported back to the reverse osmosis membrane module for treatment to meet standards before being reused.

[0077] In this invention, the tubular microfiltration membrane system is a pretreatment system. After pretreatment by the tubular microfiltration membrane system, the solution enters the reverse osmosis membrane concentration and reuse system. The concentrate produced by the reverse osmosis membrane module is used for evaporation and crystallization. The condensate from the evaporation and crystallization enters the reuse system. The water produced by the concentration unit is recycled after meeting the reuse standard.

[0078] The tubular microfiltration membrane system, used as a pretreatment, eliminates the need for PAM reagents, reducing fouling of the subsequent reverse osmosis membrane system and reducing sludge volume. The cleaning system, previously requiring separate systems for filters and ultrafiltration membranes, is reduced to a single system for the tubular microfiltration membrane. This system replaces traditional filters and ultrafiltration membranes, significantly lowering investment costs. Under the same requirements, the investment cost of tubular microfiltration is comparable to that of ultrafiltration, reducing investment costs while minimizing reclaimed water loss. The tubular microfiltration process eliminates the need for sedimentation tanks, significantly saving land and construction costs. Control is simple, reducing electrical automation costs and on-site maintenance complexity compared to a filter + ultrafiltration system. The tubular microfiltration system employs a modular design; for example, a 10-core membrane module can produce 12m³ of water per unit. 3 The system can be adjusted according to the incoming water volume, allowing for multiple sets and columns of configurations. This invention also optimizes the electrical control unit. For example, in traditional processes, each ultrafiltration membrane system requires at least 7 pneumatic (electric) valves, 3 pressure transmitters (or pressure gauges), and a corresponding electrical control system. However, the tubular microfiltration membrane system in this invention only requires 3 pneumatic (electric) valves, 1 pressure transmitter (or pressure gauge), and a corresponding electrical control system per system, significantly reducing the number of electrical control points and consequently lowering operating and maintenance costs.

[0079] Preferably, in the circulating concentration facility, when adding coagulant, defluorinating agent, ammonia water or sodium hydroxide when adding ammonium wastewater, a mixed liquid is formed. The mixed liquid enters the tubular microfiltration membrane module 1 through the circulating pump. The mixed liquid achieves solid-liquid separation through the tubular microfiltration membrane module 1, and the product water enters the reverse osmosis membrane module while the concentrate is returned to the circulating concentration facility through the circulating pump.

[0080] Understandably, in the circulating concentration facility, coagulants, defluoridators, and ammonia (sodium hydroxide for sodium-process wastewater) are added to remove heavy metal ions, phosphate ions, and fluoride ions from the water, forming precipitates. The pretreated wastewater is then pumped through a circulating pump and circulated by the membrane system before entering the subsequent tubular microfiltration membrane module 1. The wastewater in the circulating concentration facility is pumped to the tubular microfiltration membrane module 1. Due to the high-speed, intense turbulence generated by the wastewater, a large shear force is created on the membrane surface, causing the deposits on the micropores to return to the liquid. During the circulation process, permeate enters the tubular microfiltration membrane permeate tank, while the concentrate is returned to the concentration facility.

[0081] Preferably, the tubular microfiltration membrane module 1 adopts a multi-module arrangement. The circulating concentration facility is equipped with a level gauge, a sludge concentration meter, and a pH meter. The number of working modules of the tubular microfiltration membrane module 1 is adjusted according to the changing trends of the level gauge and the sludge concentration meter. When both the level gauge and the sludge concentration meter decrease, the number of working modules is reduced. When both the level gauge and the sludge concentration meter increase, the number of working modules is increased. When the level gauge decreases and the sludge concentration meter increases, the number of working modules is reduced. When the level gauge increases and the sludge concentration meter decreases, the number of working modules is increased.

[0082] The method of this invention utilizes the high-flux circulation of a tubular microfiltration membrane system and the large-area sludge concentration within the circulation tank (sludge concentration design value: operation between 2500 mg / L and 80000 mg / L) to achieve the following functions:

[0083] 1) This invention solves the problem of water quality impacting system load: Tubular microfiltration membrane elements commonly have 1, 4, or 10 cores, with circulating water volumes reaching 16m³ / h. 3 / h、32m 3 / h、86m 3 / h, can quickly homogenize water quality, such as a water volume of 120m³. 3 The system uses a 10-core membrane element and a 5-hour residence time in the circulation tank. The water in the circulation tank can complete one cycle in just 0.69 hours, achieving rapid and uniform water quality.

[0084] 2) This invention solves the problem of water volume impact load on the system: In the iron phosphate synthesis reaction process, due to the non-uniqueness of impurities in ferrous sulfate, the particle size and surface impurities of iron phosphate after the reaction may not meet the standards. Therefore, the water quality and quantity are different when washing each batch of materials. How to maintain the stable operation of the treatment system has always been a problem in the industry.

[0085] In the circulating concentration facility of the tubular microfiltration membrane system of this invention, in addition to the matching level gauge, a sludge concentration meter and a level gauge are also provided. The following functions are achieved by interlocking the level gauge and the sludge concentration meter:

[0086]

[0087] Based on the information in the table above, an effective method is provided to address the impact of water surges and maintain system stability.

[0088] Preferably, the ferric phosphate wastewater includes wash water and mother liquor, or a mixture of wash water and mother liquor. The evaporator in the evaporation and crystallization step is a triple-effect evaporator, an MVR evaporator, or a combination of multi-effect and freeze crystallization evaporator. For ammonium process wastewater, the evaporation system separates ammonium sulfate, monoammonium phosphate, and miscellaneous salts. For sodium process wastewater, the evaporation system separates sodium sulfate and miscellaneous salts. The condensate from the evaporation system is treated in a pure water system and reused after meeting standards.

[0089] Example 1

[0090] This embodiment describes a comprehensive treatment method for ferric phosphate wastewater (ammonia method). The influent water quality indicators are shown in the table below:

[0091] Table 1. Influent water quality in Example 1

[0092] Mother liquor index unit Wash water index unit ammonia nitrogen content 6.18 g / L ammonia nitrogen content 0.751 g / L phosphate 6.05 g / L phosphate 0.731 g / L sulfate 0.44 mol / L sulfate 0.054 mol / L <![CDATA[Fe 3+ ]]> 50 mg / L <![CDATA[Fe 3+ ]]> 5 mg / L <![CDATA[F - ]]> 67 mg / L <![CDATA[F - ]]> 7 mg / L <![CDATA[Ca 2+ ]]> 30 mg / L <![CDATA[Ca 2+ ]]> 5 mg / L <![CDATA[Mg 2+ ]]> 800 mg / L <![CDATA[Mg 2+ ]]> 150 mg / L <![CDATA[Mn 2+ ]]> 120 mg / L <![CDATA[Mn 2+ ]]> 30 mg / L

[0093] Product and reuse requirements in this embodiment:

[0094] Based on the characteristics of the wastewater, industrial products such as ammonium sulfate, monoammonium phosphate (monoammonium dihydrogen phosphate), and calcium magnesium phosphate fertilizer can be recovered. Condensate and pure water can also be recovered for reuse within the plant. Byproducts: Ammonium sulfate, ammonium dihydrogen phosphate (ammonium dihydrogen phosphate w / % ≥ 80%), and magnesium ammonium phosphate after drying (at least qualified products).

[0095] Reclaimed water requirements: The conductivity of reclaimed water is less than 10 μS / cm, pH: 6-7, which meets the water requirements for ferric phosphate production.

[0096] Please refer to the attached instruction manual for the process flow diagram. Figure 2 This embodiment consists of a wash water treatment system and a mother liquor treatment system, and the process flow is described below:

[0097] 1. Equalization Tank. This tank stores and buffers wastewater while also homogenizing it. However, by adjusting the wastewater retention time in a circulating thickening system, the high-flow-rate circulation of the tubular microfiltration membrane and the thickening system can quickly homogenize both the quantity and quality of the water, thus eliminating the need for an equalization tank and reducing the need for a booster pump to subsequent systems.

[0098] 2. Pretreatment. A tubular microfiltration membrane system is used. Tubular microfiltration membranes are characterized by wide flow channels, strong corrosion resistance, turbulent material flow within the tubes, ease of cleaning, and tolerance for relatively high solids content within the membrane tubes, typically 1%-5%, making them suitable for materials with high solids content. The principle is based on sieving, using pressure difference to drive membrane separation.

[0099] In this embodiment, the tubular microfiltration membrane system consists of a circulating concentration facility and a tubular microfiltration membrane module 1. PAC, defluorinating agent, ammonia, etc., are added to the circulating concentration facility. A circulating pump enables the circulating concentration facility and the tubular microfiltration membrane to achieve circulation and concentration. Simultaneously, the membrane system completes solid-liquid separation during concentration. The circulating concentration facility can discharge sludge periodically, or the discharge can be initiated after the design value is reached, as measured by a sludge concentration meter.

[0100] This invention eliminates the need for PAM addition, which incurs costs and generates secondary treatment costs (sludge). This method reduces sludge production by 30%, and the effluent can directly enter the RO system. The effluent is free of PAM, microorganisms, and suspended solids (SS), with an SDI of less than 3, thus protecting the RO membrane and extending its lifespan.

[0101] 3. Reverse osmosis membrane concentration and reuse. The primary function of a reverse osmosis unit is desalination, utilizing the characteristics of the reverse osmosis membrane to remove soluble salts, colloids, organic matter, and microorganisms from the water. The final product water from the reverse osmosis system is sent to the reuse system, while the concentrate, after reaching the designed concentration, enters the evaporation and crystallization system.

[0102] 4. Evaporation and Crystallization. The concentrated water from the reverse osmosis concentration and reuse system contains ammonium sulfate and monoammonium phosphate. By utilizing the evaporation and concentration action of the evaporator, ammonium sulfate, monoammonium phosphate, and other salts are separated under the action of steam.

[0103] The washing water treatment system design in this embodiment is as follows:

[0104] Water treatment capacity 185m³ 3 / h, after homogenization in the wash water equalization tank, the water is pumped to the wash water circulation concentration facility using a lift pump. An appropriate amount of ammonia water is added to the wash water circulation concentration facility (pH adjusted to 8-9), and a quantitative amount of defluorinating agent is added simultaneously. Under alkaline conditions, most metal ions form insoluble precipitates. The mixed liquid achieves solid-liquid separation through the wash water tubular microfiltration membrane module 1. Its permeate enters the wash water tubular microfiltration membrane permeate tank, and the concentrated water is returned to the wash water circulation concentration facility. The sludge in the wash water circulation concentration facility enters the sludge tank through the sludge pump 4 and is then filtered by the filter press.

[0105] The permeate from the wash water tubular microfiltration membrane system is pumped to the wash water RO system. The permeate from the wash water RO system then undergoes primary and secondary purification systems to produce pure water for reuse. The concentrate from the wash water RO system enters the concentrate tank of the concentrate RO system, and then flows through the wash water concentrate RO system. The concentrate from the wash water concentrate RO system enters the mother liquor tubular microfiltration membrane permeate tank, and the permeate is then delivered to the wash water RO system permeate tank.

[0106] The mother liquor treatment system design in this embodiment is as follows:

[0107] Water treatment capacity 90m³ 3 / h, after homogenization in the mother liquor equalization tank, the mixture is pumped to the mother liquor concentration facility using a lift pump. An appropriate amount of ammonia water is added to the mother liquor concentration facility (pH adjusted to 8-9), and a quantitative amount of defluorinating agent is added simultaneously. Under alkaline conditions, most metal ions form insoluble precipitates. The mixed liquor achieves solid-liquid separation through the mother liquor tubular microfiltration membrane. The permeate enters the mother liquor tubular microfiltration membrane permeate tank, and the concentrated water is returned to the mother liquor concentration facility. The sludge in the mother liquor concentration facility enters the sludge tank through the sludge pump 4 and is then filtered by a filter press.

[0108] The permeate from the mother liquor tubular microfiltration membrane system is pumped to the mother liquor RO system by a booster pump. The concentrate from the mother liquor RO system enters the MVR feed tank, and the permeate is sent to the permeate tank of the wash water RO system.

[0109] The concentrated water entering the evaporation and crystallization system must have a TDS of not less than 160 g / L.

[0110] The evaporation crystallization system can adopt triple-effect, MVR, or a combination of multi-effect and freeze crystallization processes. This case adopts the MVR solution. The evaporation system separates ammonium sulfate, miscellaneous salts and ammonium phosphate, etc. The condensate from the evaporation system enters the pure water system for treatment and is reused after meeting the standards.

[0111] Example 2

[0112] This embodiment describes a comprehensive treatment method for ferric phosphate wastewater (sodium method). The influent water quality indicators are shown in the table below:

[0113] Table 2. Influent water quality in Example 2

[0114] Serial Number project Sodium process mother liquor Sodium washing water 1 Water temperature (°C) 45 45 2 pH 2-2.5 2-2.5 3 F (ppm) Not detected Not detected 4 Na (ppm) 39322 254 5 <![CDATA[NH4 + (ppm)]]> 37 19 6 <![CDATA[SO4 2- (ppm)]]> 67018 433 7 P (ppm) 1145 240 8 Fe (ppm) 984 170 9 Ca (ppm) 264 103 10 Mg (ppm) 1209 84 11 Mn (ppm) 546 37 12 COD (ppm) 149 19

[0115] Product and reuse requirements for this embodiment:

[0116] Based on the characteristics of the wastewater, anhydrous sodium sulfate (sodium sulfate) industrial products can be reused.

[0117] Reclaimed water requirements: The conductivity of reclaimed water is less than 10 μS / cm, pH is 6-7, and it meets the water requirements for ferric phosphate production.

[0118] Please refer to Appendix 3 of the instruction manual for the process flow diagram. The main process of this embodiment is the same as that of Embodiment 1, and it is also divided into a washing water treatment system and a mother liquor treatment system. The specific washing water and mother liquor treatment process flow is described as follows:

[0119] Washing water treatment system design:

[0120] Water treatment capacity 670m³ 3The water is homogenized in the wash water equalization tank and then pumped to the wash water circulation and concentration facility. An appropriate amount of sodium hydroxide is added to the wash water circulation and concentration facility (pH adjusted to 8-9), and a quantitative amount of defluorinating agent is added simultaneously. Under alkaline conditions, most metal ions form insoluble precipitates. The mixed liquid is separated into solid and liquid by passing through the wash water tubular microfiltration membrane. The permeate enters the wash water tubular microfiltration membrane permeate tank, and the concentrated water is returned to the wash water circulation and concentration facility. The sludge in the wash water circulation and concentration facility is pumped into the sludge tank and then filtered by a filter press.

[0121] The permeate from the wash water tubular microfiltration membrane system is pumped to the wash water RO system. The permeate from the wash water RO system then undergoes primary and secondary purification systems to produce pure water for reuse. The concentrate from the wash water RO system enters the concentrate tank of the concentrate RO system, and then flows through the wash water concentrate RO system. The concentrate from the wash water concentrate RO system enters the mother liquor tubular microfiltration membrane permeate tank, and the permeate is then delivered to the wash water RO system permeate tank.

[0122] Mother liquor treatment system design:

[0123] Water treatment capacity 270m³ 3 / h, after homogenization in the mother liquor equalization tank, the mixture is pumped to the mother liquor circulation concentration facility using a lift pump. An appropriate amount of sodium hydroxide is added to the mother liquor circulation concentration facility (to level 8-9 in the equalization tank), and a quantitative amount of defluorinating agent is added simultaneously. Under alkaline conditions, most metal ions form insoluble precipitates. The mixed liquor undergoes solid-liquid separation through a mother liquor tubular microfiltration membrane. The permeate enters the mother liquor tubular microfiltration membrane permeate tank, while the concentrated water is returned to the mother liquor concentration facility. The sludge in the mother liquor concentration facility is pumped into the sludge tank and then filtered by a filter press.

[0124] The permeate from the mother liquor tubular microfiltration membrane system is pumped to the mother liquor RO system by a booster pump. The concentrate from the mother liquor RO system enters the MVR feed tank, and the permeate is sent to the permeate tank of the wash water RO system.

[0125] The permeate from the mother liquor tubular microfiltration membrane system is concentrated and separated by a membrane concentration and reuse system. The final permeate is recovered and reused, and the TDS of the concentrated water is required to be no less than 130 g / L before entering the evaporation and crystallization system.

[0126] The evaporation crystallization system can employ a triple-effect, MVR, or multi-effect combined with freeze crystallization processes. This embodiment uses an MVR + freeze crystallization solution. The evaporation system separates sodium sulfate, miscellaneous salts, and freeze-crystallized sodium phosphate, etc. The condensate from the evaporation system is treated in a pure water system and reused after meeting standards.

[0127] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0128] This document describes the principles and implementation methods of the present invention. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A ferric phosphate wastewater treatment system, characterized in that, The system includes a circulating thickening facility and a tubular microfiltration membrane module (1). The sludge discharge port of the circulating thickening facility is connected to a filter press via a sludge pump (4). The outlet of the circulating thickening facility is connected to a regulating pipe (2) for regulating water flow via a circulating pump (3). The regulating pipe (2) is equipped with a detachable inner tube assembly and a detachable filter screen assembly. The regulating pipe (2) is connected to the inlet pipe (16) of the tubular microfiltration membrane module (1). The tubular microfiltration membrane module (1) is followed by a tubular microfiltration membrane permeate tank and a reverse osmosis membrane module. The reverse osmosis membrane module is connected to a steam distillation tank and a reverse osmosis membrane module, respectively. The generator and the reverse osmosis membrane permeate tank are connected. The reverse osmosis membrane permeate tank is connected to the return water tank, and the reverse osmosis membrane permeate tank is connected to the tubular microfiltration membrane permeate tank through a return pipe. The filter assembly includes a filter screen (15), which is located at one end of the inner tube (12). The filter screen (15) is installed on the outer tube (5) by a limiting component (14) symmetrically arranged along the radial direction of the filter screen (15). The limiting component (14) includes a first vertical plate (17) and a second vertical plate (21) arranged in parallel. Both the first vertical plate (17) and the second vertical plate (21) penetrate the outer tube. 5) The pipe wall is set and the two are located outside the outer pipe (5) at one end, which is connected by the top plate (18). The first vertical plate (17) is located inside the outer pipe (5) at one end, which is connected to the inner pipe (12). The other end of the first vertical plate (17) is provided with a mounting plate (8). The mounting plate (8) is provided with a screw hole for threaded connection with the adjusting rod (6) of the screw structure. The outer pipe (5) is provided with a bearing. The bottom of the adjusting rod (6) is connected to the bearing. The filter screen (15) is located between the first vertical plate (17) and the second vertical plate (21). The adjusting pipe (2) includes the outer pipe (5). (5) An inner tube assembly is provided inside, the inner tube assembly includes an inner tube (12), and there is a spacer cavity (13) between the outer tube (5) and the inner tube (12). An elastic splice part (9) is provided on the tube wall of the inner tube (12), and an adjustment component is provided on the tube wall of the outer tube (5). The adjustment component is used to squeeze or stretch the elastic splice part (9) to adjust the diameter of the inner tube (12). The two ends of the inner tube (12) are connected to the outer tube (5) through a sealing element (11). The sealing element (11) is used to seal the spacer cavity (13) between the inner tube (12) and the outer tube (5).

2. The ferric phosphate wastewater treatment system according to claim 1, characterized in that, The inner tube (12) includes multiple arc-shaped tube walls, and adjacent arc-shaped tube walls are spliced ​​together by an elastic splicing part (9); the sealing element (11) includes multiple elastic sealing strips and an elastic connecting part (10) provided between adjacent elastic sealing strips. The elastic sealing strips and the arc-shaped tube walls are provided in a one-to-one correspondence. The elastic connecting part (10) is used to be driven to be squeezed or stretched synchronously with the elastic splicing part (9) when adjusting the diameter of the inner tube (12).

3. The ferric phosphate wastewater treatment system according to claim 1, characterized in that, The adjustment assembly includes an adjustment plate (7) that penetrates the wall of the outer tube (5). The first end of the adjustment plate (7) is connected to the wall of the inner tube (12). The second end of the adjustment plate (7) is located outside the outer tube (5) and is provided with a mounting plate (8). The mounting plate (8) is provided with a screw hole. The wall of the outer tube (5) is provided with a bearing. The adjustment assembly also includes an adjustment rod (6) that is connected to the bearing and axially fixed relative to the bearing. The adjustment rod (6) is a lead screw. The adjustment rod (6) passes through the screw hole and is threadedly connected to the screw hole.

4. The ferric phosphate wastewater treatment system according to claim 1, characterized in that, A spring (19) is pressed between the filter screen (15) and the top plate (18). The cross-sectional length of the second vertical plate (21) is longer than that of the first vertical plate (17). A support part (22) is provided on the second vertical plate (21). The support part (22) is used to support the side of the filter screen (15). A conical tube-shaped guide part (23) is provided at the tail end of the support part (22).

5. A method for treating ferric phosphate wastewater, using the ferric phosphate wastewater treatment system according to any one of claims 1-4, characterized in that, Includes the following steps: S100, Pretreatment: The iron phosphate wastewater is pretreated using a tubular microfiltration membrane system, which includes a circulating concentration facility and a tubular microfiltration membrane module (1). S101. Ferric phosphate wastewater first enters the circulating concentration facility for preliminary filtration. S102. Wastewater from the circulating concentration facility enters the tubular microfiltration membrane module (1) for microfiltration treatment; S200, Reverse Osmosis Membrane Concentration and Reuse: S201. The product water from the tubular microfiltration membrane module (1) is pumped to the reverse osmosis membrane module for reverse osmosis filtration. S202. The permeate from the reverse osmosis membrane module is treated by the pure water system and then enters the recycled water tank, while the concentrate from the reverse osmosis membrane module enters the evaporation and crystallization system. S300, Evaporation and Crystallization: S301. The concentrate from the reverse osmosis membrane module is evaporated and concentrated using an evaporator to produce crystalline salt and condensate. The condensate is then transported back to the reverse osmosis membrane module for treatment to meet standards before being reused.

6. The method for treating ferric phosphate wastewater according to claim 5, characterized in that, In step S101, coagulant, defluorinating agent, ammonia or sodium hydroxide are added to the circulating concentration facility to form a mixed liquid. The mixed liquid enters the tubular microfiltration membrane module (1) through the circulating pump. The mixed liquid achieves solid-liquid separation through the tubular microfiltration membrane module (1), and the product water enters the reverse osmosis membrane module while the concentrate is returned to the circulating concentration facility by the circulating pump. The sludge generated in the circulating concentration facility in step S101 is discharged and then pressure filtered to produce solid by-products.

7. The method for treating ferric phosphate wastewater according to claim 5, characterized in that, The tubular microfiltration membrane module (1) adopts a multi-module arrangement. The circulating concentration facility is equipped with a level gauge, a sludge concentration meter and a pH meter. The number of working modules of the tubular microfiltration membrane module is adjusted according to the changing trends of the level gauge and the sludge concentration meter. When both the level gauge and the sludge concentration meter decrease, the number of working modules is reduced. When both the level gauge and the sludge concentration meter increase, the number of working modules is increased. When the level gauge decreases and the sludge concentration meter increases, the number of working modules is reduced. When the level gauge increases and the sludge concentration meter decreases, the number of working modules is increased.

8. The method for treating ferric phosphate wastewater according to claim 5, characterized in that, The ferric phosphate wastewater includes wash water and mother liquor or a mixture of wash water and mother liquor. The evaporator in step S301 is a triple-effect evaporator, an MVR evaporator, or a combination of multi-effect and freeze crystallization evaporator.

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