A semiconductor industry fluorine-containing wastewater treatment system and method

Abstract

The present invention discloses a system and method for treating fluorine-containing wastewater from the semiconductor industry. The treatment system includes a regulating unit, a pretreatment unit, a phosphorus recovery unit, a biochemical treatment and membrane separation unit, and a phosphorus release and decalcification unit. The phosphorus release and decalcification unit is used to release phosphorus from the membrane separation concentrate and, after cyclone enrichment, enter the phosphorus recovery unit together with the partially hydrolyzed acidified water from the biochemical treatment and membrane separation unit. The phosphorus recovery unit utilizes the high pH value of the pretreatment unit and uses unprecipitated calcium fluoride, newly generated calcium fluoride, and calcium phosphate and calcium fluoride refluxed from the phosphorus release and decalcification unit as crystal nuclei to induce calcium ions and phosphate ions in the wastewater to rapidly form calcium fluoride and calcium phosphate. The calcium fluoride and calcium phosphate are ultimately removed from the system through physical and chemical sludge removal and phosphorus product recovery. This reduces the impact of calcium ions on the MBR membrane, improves phosphorus recovery, reduces the amount of precipitant used and the amount of sludge, reduces chemical consumption, and ensures stable operation of the biochemical system.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a system and method for treating fluorine-containing wastewater in the semiconductor industry. Background Art

[0002] The existing methods for treating fluorine-containing wastewater in the semiconductor industry mainly include chemical precipitation, coagulation and precipitation, adsorption, and crystallization. Among them, the chemical precipitation method is to add chemical agents to the fluorine-containing wastewater to form a precipitate with fluoride ions and precipitants (lime, calcium chloride, calcium carbonate, etc.), and then remove fluorine after solid-liquid separation. The two-stage defluorination process with chemical precipitation as the core, namely "primary reaction + primary flocculation + primary precipitation + secondary reaction + secondary flocculation + secondary precipitation", is currently widely used in the treatment of large-scale high-concentration fluorine-containing wastewater due to its simple operation, low investment, and obvious defluorination effect. The COD value of the wastewater after defluorination is still very high, and it needs to enter the biochemical and membrane separation system for further treatment before it can meet the discharge standards. The main disadvantages of the existing two-stage defluorination process are:

[0003] (1) The calcium fluoride generated by the reaction is wrapped around the surface of the precipitant particles, hindering the further reaction of the precipitant inside the particles, reducing the efficiency of the precipitant, increasing the amount of precipitant used and the amount of sludge. At the same time, the unreacted precipitant and residual calcium fluoride affect the stable operation of the subsequent biochemical treatment system. This is because high concentrations of calcium ions are inhibitors of activated sludge. Usually, continuous inoculation of activated sludge is required to maintain the normal operation of the biochemical treatment system. In addition, calcium fluoride is a membrane contaminant that is extremely difficult to clean and can easily cause membrane clogging and reduce membrane separation efficiency.

[0004] (2) During the precipitation reaction, it is necessary to control the pH of the wastewater to be in the range of 9 to 12 by adding alkali to facilitate the formation of calcium fluoride. After the reaction is completed, it is necessary to adjust the pH of the wastewater to 6 to 9 by adding acid to meet the requirements of the subsequent biochemical treatment system. Therefore, a large amount of acid and alkali reagents are used.

[0005] (3) Wastewater is rich in phosphorus. The existing two-stage defluorination process has a low phosphorus recovery rate. The unrecovered phosphorus enters the biochemical treatment system, increasing the load of the biochemical treatment and causing a waste of phosphorus resources.

[0006] (4) The existing technology mainly uses precipitation method for phosphorus removal. The pH of the wastewater after the two-stage defluorination process is relatively low. When the precipitation method is used for phosphorus removal, it is necessary to control the pH to 9-10 by adding alkali to facilitate the formation of calcium phosphate. After the reaction, it is necessary to control the pH to 6-9 by adding acid to meet the requirements of the subsequent treatment system or discharge. The amount of acid and alkali agents used is relatively large. Summary of the Invention

[0007] In order to solve the technical problems of large amount of precipitant and reagent usage, low phosphorus recovery rate and unstable operation of subsequent biochemical treatment system in the existing fluorine-containing wastewater treatment process, the present invention provides a semiconductor industry fluorine-containing wastewater treatment system and method.

[0008] The technical solution adopted in the present invention is:

[0009] A semiconductor industry fluorine-containing wastewater treatment system, comprising:

[0010] Regulating unit, used to balance the influent water quality and quantity;

[0011] The pretreatment unit is used to add chemical agents to the conditioned wastewater to cause fluoride ions to form precipitation with the precipitant, and then discharge it from the system in the form of physical and chemical sludge after solid-liquid separation to achieve fluoride removal;

[0012] The phosphorus recovery unit is used to add a precipitant to the pretreated wastewater to form phosphate ions. After solid-liquid separation, the precipitate is discharged from the system in the form of physicochemical sludge to achieve further fluoride removal and phosphorus recovery.

[0013] A biochemical treatment and membrane separation unit for removing organic matter from the wastewater after phosphorus recovery through microbial degradation and membrane separation; and

[0014] The phosphorus release and calcium removal unit is used to release the phosphorus in the membrane separation concentrated water and enter the phosphorus recovery unit together with the partially hydrolyzed acidified water from the biochemical treatment and membrane separation units after cyclone enrichment, so that the calcium fluoride and calcium phosphate remaining in the biochemical system are removed from the system in the form of physical and chemical sludge.

[0015] Furthermore, the regulating unit includes a regulating tank, a first aeration device is provided at the bottom of the regulating tank, and the first aeration device is connected to the biochemical aeration main pipe of the biochemical treatment and membrane separation unit.

[0016] Furthermore, the pretreatment unit includes a mixing reaction tank, a coagulation reaction tank, a flocculation reaction tank and a sedimentation tank which are connected in sequence. Part of the sludge in the sedimentation tank is discharged, and part of it flows back to the flocculation reaction tank.

[0017] Furthermore, an alkali solution and precipitant dosing device is provided in the mixing reaction tank, and a second aeration device is provided at the bottom of the coagulation reaction tank. The second aeration device is connected to the membrane scrubbing aeration main pipe of the biochemical treatment and membrane separation unit.

[0018] Furthermore, the phosphorus recovery unit includes a phosphorus recovery tank and a mixing buffer tank. The phosphorus recovery tank is provided with a precipitant dosing device. After solid-liquid separation in the phosphorus recovery tank, the precipitated sludge is partially discharged to recover phosphorus, and partially merged with the sludge in the sedimentation tank of the pretreatment unit; the supernatant of the sedimentation separation enters the mixing buffer tank.

[0019] Furthermore, a sulfuric acid dosing device and a stirrer are provided in the mixing buffer tank.

[0020] Furthermore, the biochemical treatment and membrane separation unit includes a hydrolysis and acidification tank, an anoxic tank, an aerobic tank and an MBR membrane tank connected in sequence; part of the effluent from the hydrolysis and acidification tank is pumped into the phosphorus release unit and enters the phosphorus recovery unit together with the wastewater from the phosphorus release unit to recover phosphorus.

[0021] Furthermore, the hydrolysis and acidification tank is equipped with a domestic sewage inlet pipe. Domestic sewage is rich in phosphorus, and biochemical treatment with the defluoridated wastewater can improve phosphorus recovery efficiency. Continuously inoculating sludge with domestic sewage to the defluoridated wastewater can also reduce the inhibitory effect of high calcium ion concentrations on activated sludge, maintaining the normal operation of the biochemical treatment system.

[0022] Furthermore, the phosphorus release and calcium removal unit includes a reflow tank, a mud phase enrichment cyclone, a biological phosphorus release tank and a water phase enrichment cyclone; the membrane separation concentrated water enters the reflow tank and is pumped to the mud phase enrichment cyclone for centrifugal separation, the separated light components are discharged as biological sludge, and the heavy components enter the biological phosphorus release tank; the mud water in the biological phosphorus release tank is pumped together with the partially hydrolyzed acidified water of the biochemical treatment and membrane separation unit to the water phase enrichment cyclone for centrifugal separation, the separated light components enter the anoxic tank of the biochemical treatment and membrane separation unit, and the heavy components enter the phosphorus recovery unit together with the effluent of the pretreatment unit.

[0023] A method for treating fluorine-containing wastewater in the semiconductor industry using any of the above-mentioned systems comprises the following steps:

[0024] (1) After the fluorine-containing wastewater is regulated in water quality and quantity by the regulating unit, it enters the pretreatment unit;

[0025] (2) In the pretreatment unit, the wastewater is first mixed with NaOH and CaCl2, and then subjected to coagulation and flocculation followed by sedimentation separation. During this process, fluoride ions form calcium fluoride sludge, which is discharged in the form of physical and chemical sludge. The supernatant of sedimentation separation enters the phosphorus recovery unit;

[0026] (3) In the phosphorus recovery unit, fluoride ions are further removed by adding CaCl2 precipitant to the wastewater, and the phosphorus ions in the wastewater react with CaCl2 to form calcium phosphate precipitates. Phosphorus is recovered after solid-liquid separation, and the calcium fluoride sludge is discharged as physical and chemical sludge. The supernatant of the sedimentation separation is adjusted with H2SO4 to adjust the pH value and then enters the biochemical treatment and membrane separation unit;

[0027] (4) In the biochemical treatment and membrane separation unit, the wastewater undergoes hydrolysis and acidification, anoxic treatment, and aerobic treatment in sequence, and then passes through the MBR membrane to separate organic matter, harmful substances, and salts, and is discharged in compliance with the standards; the membrane separation concentrated water enters the phosphorus release unit;

[0028] (5) In the phosphorus release and calcium removal unit, the calcium fluoride and calcium phosphate remaining in the biochemical system are enriched by using a mud phase enrichment cyclone and then sent to the biological phosphorus release pool. The biological phosphorus release pool releases the phosphorus in the mud water, which is then combined with the partially hydrolyzed acidified water from the biochemical treatment and membrane separation units and then enriched by the water phase enrichment cyclone and enters the phosphorus recovery unit.

[0029] Beneficial effects of the present invention:

[0030] By setting up a phosphorus recovery unit between the pretreatment unit and the biochemical treatment and membrane separation unit, the high pH of the effluent from the sedimentation tank of the pretreatment unit can be directly used for precipitation and phosphorus removal, reducing the amount of alkali added. In addition, it is only necessary to add acid once for pH adjustment after phosphorus removal, reducing the amount of acid added, thereby greatly reducing the amount of acid and alkali agents used in the entire system.

[0031] 2. Through the combination of the phosphorus recovery unit and the phosphorus release and calcium removal unit, the phosphorus release and calcium removal unit can enrich the calcium fluoride and calcium phosphate remaining in the biochemical system and then enter the phosphorus recovery unit, and finally remove them from the system in the form of physical and chemical sludge and phosphorus products, thereby reducing the impact of calcium ions on the MBR membrane; the phosphorus recovery unit utilizes the high pH value of the pretreatment unit, and uses unprecipitated calcium fluoride, newly generated calcium fluoride, and calcium phosphate and calcium fluoride refluxed from the phosphorus release and calcium removal unit as crystal nuclei to induce calcium ions and phosphate ions in the wastewater to quickly form calcium fluoride and calcium phosphate, and finally remove them from the system through physical and chemical sludge discharge and phosphorus product recovery, thereby improving the phosphorus recovery rate, reducing the amount of precipitant used and the amount of sludge, and ensuring the stable operation of the biochemical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a flow chart of the fluorine-containing wastewater treatment system of Example 1 of the present invention.

[0033] In the figure: 100 regulating unit, 200 pretreatment unit, 300 phosphorus recovery unit, 400 membrane separation unit, 500 phosphorus release and calcium removal unit, 1 regulating tank, 2 mixing reaction tank, 3 coagulation reaction tank, 4 flocculation reaction tank, 5 sedimentation tank, 6 phosphorus recovery tank, 7 mixing buffer tank, 8 hydrolysis acidification tank, 9 membrane grid, 10 anoxic tank, 11 aerobic tank, 12 MBR membrane tank, 13 reflow tank, 14 water phase enrichment cyclone, 15 biological phosphorus release tank, 16 mud phase enrichment cyclone, 17 biochemical aeration fan, 18 membrane scrubbing fan. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and a preferred embodiment. Example 1

[0035] See Figure 1 This embodiment provides a semiconductor industry fluorine-containing wastewater treatment system, including a regulating unit 100, a pretreatment unit 200, a phosphorus recovery unit 300, a biochemical treatment and membrane separation unit 400, and a phosphorus release and calcium removal unit 500.

[0036] The regulating unit 100 includes a regulating tank 1. In this embodiment, a first aeration device is provided at the bottom of the regulating tank 1. The first aeration device includes an aerator and an aeration branch pipe. The aeration branch pipe is connected to the biochemical aeration main pipe of the biochemical treatment and membrane separation unit 400 through an aeration valve.

[0037] The effluent from the regulating tank 1 flows into the mixing reaction tank 2 by gravity.

[0038] The pretreatment unit 200 includes a mixing reaction tank 2, a coagulation reaction tank 3, a flocculation reaction tank 4 and a sedimentation tank 5 which are connected in sequence.

[0039] The mixing reaction tank 2 is provided with sodium hydroxide and calcium chloride reagent addition points, the main functions of which are to add alkali to adjust the pH and add precipitant to promote the reaction of fluoride ions and calcium ions in the wastewater to generate calcium fluoride.

[0040] In this embodiment, the mixing reaction tank 2 is also equipped with a second aeration device and an agitator. The second aeration device includes an aerator and an aeration branch pipe. The aeration branch pipe is connected to the membrane scrubbing aeration main pipe of the biochemical treatment and membrane separation unit 400 via an aeration valve. The high air volume of the membrane scrubbing aeration system intermittently flushes the calcium fluoride particles generated by the reaction, preventing them from being coated on the surface of the precipitant particles. This improves the efficiency of the precipitant and reduces the amount of precipitant used and the amount of sludge.

[0041] A coagulant addition point is provided in the coagulation reaction tank 3, the main function of which is to add coagulant so that calcium fluoride and coagulant fully react to form flocs, which is conducive to sedimentation and separation.

[0042] A flocculant addition point is provided in the flocculation reaction tank 4, the main function of which is to add flocculant so that calcium fluoride and flocculant fully react to form flocs, which is conducive to sedimentation and separation.

[0043] Sedimentation tank 5 primarily performs sedimentation separation, removing calcium fluoride-rich flocs from the system through settling. After sedimentation and separation, the supernatant overflows into phosphorus recovery tank 6, while the sludge partially flows back into flocculation tank 4. The remaining sludge is discharged to the physicochemical sludge treatment unit.

[0044] The phosphorus recovery unit 300 includes a phosphorus recovery tank 6 and a mixing buffer tank 7 .

[0045] The phosphorus recovery tank 6 is provided with a calcium chloride dosing point, the main functions of which are: (1) further removing fluoride by dosing calcium chloride twice; (2) using the calcium fluoride that has not been completely precipitated in the sedimentation tank and the calcium fluoride generated by the newly added calcium chloride to provide crystal nuclei to induce the rapid formation of calcium fluoride; (3) using the high pH of the sedimentation tank to precipitate calcium phosphate in the wastewater and recover phosphorus in the wastewater; (4) using the calcium phosphate refluxed from the phosphorus release and calcium removal unit 500 to provide crystal nuclei to induce the rapid formation of calcium phosphate.

[0046] After pretreatment, the wastewater undergoes solid-liquid separation in the phosphorus recovery tank 6. The supernatant flows by gravity into the mixing buffer tank 7. The sludge is partially returned to the sludge return line of the sedimentation tank 5, and the remaining portion is discharged to the phosphorus product recovery unit for phosphorus recovery. The calcium phosphate and calcium fluoride rich in the returned sludge act as crystal nuclei to enhance the reaction efficiency of the flocculation reaction tank.

[0047] A sulfuric acid addition point is provided in the mixing buffer tank 7, the main function of which is to add sulfuric acid to neutralize the high pH caused by the addition of sodium hydroxide in the mixing reaction tank, thereby ensuring the normal operation of the biochemical system.

[0048] The biochemical treatment and membrane separation unit 400 includes a hydrolysis and acidification tank 8, a membrane grid 9, an anoxic tank 10, an aerobic tank 11, an MBR membrane tank 12, a biochemical aeration blower 17, and a membrane scrubbing blower 18, all connected in sequence. The anoxic tank, aerobic tank, membrane tank, recirculation tank, and aeration system are designed according to conventional processes. Water from the hydrolysis and acidification tank 8 is partially pumped into an aqueous phase enrichment cyclone 14.

[0049] In addition, a domestic sewage inlet can be provided in the hydrolysis and acidification tank 8. By introducing domestic sewage, the impact of inhibitors such as calcium ions on the biochemical treatment system is reduced, lowering or eliminating the operating costs of continuous inoculation. Furthermore, the high phosphorus content of domestic sewage sludge improves the operating efficiency of the phosphorus recovery unit.

[0050] The produced water from the MBR membrane pool 12 is discharged, and the concentrated water enters the recirculation pool 13.

[0051] The phosphorus release and decalcification unit 500 includes a reflow tank 13 , a mud phase enrichment cyclone 16 , a biological phosphorus release tank 15 and a water phase enrichment cyclone 14 .

[0052] The effluent from the recirculation tank 13 is pumped into the sludge phase enrichment cyclone 16 , and the light components overflowing from the top of the sludge phase enrichment cyclone are discharged to the biological sludge treatment system, while the heavy components at the bottom flow by gravity into the biological phosphorus release tank 15 .

[0053] The functions of the mud phase enrichment cyclone 16 are: (1) to enrich the calcium fluoride and calcium phosphate remaining in the biochemical system, and finally remove them from the system through physical and chemical sludge discharge and phosphorus product recovery, thereby reducing the impact of calcium fluoride and calcium phosphate on the MBR membrane; (2) to increase the sludge concentration, improve the sludge concentration and phosphorus release effect of the biological phosphorus release tank.

[0054] The function of the biological phosphorus release tank 15 is: under anaerobic conditions in the absence of dissolved oxygen and nitrate nitrogen, facultative bacteria convert dissolved organic matter into volatile fatty acids, so that the phosphorus removal bacteria obtain volatile fatty acids. The phosphorus removal bacteria then absorb the volatile fatty acids produced in the anaerobic microbial phosphorus release tank and transport them into the cells, where they are assimilated into fermentation of intracellular sugars and lead to the release of phosphorus.

[0055] The effluent from the biological phosphorus release tank is pumped together with the effluent from the hydrolysis and acidification tank into the water phase enrichment cyclone 14. The light components separated by the water phase enrichment cyclone 14 are returned to the anoxic tank 10 to serve as a biological internal carbon source to promote denitrification and denitrification. The separated heavy components are sent to the phosphorus recovery tank 6 together with the effluent from the sedimentation tank to enrich the calcium fluoride and calcium phosphate remaining in the biochemical system and finally removed from the system through physical and chemical sludge discharge and phosphorus product recovery. Example 2

[0056] This embodiment provides a method for treating fluoride-containing wastewater using the treatment system described in Example 1, wherein the fluoride ion concentration in the fluoride-containing wastewater is 30 mg / L and the total phosphorus concentration is 6 mg / L:

[0057] (1) Fluoride-containing wastewater enters regulating tank 1, where it is adjusted for water quality and quantity before entering mixing reaction tank 2; the hydraulic retention time in the regulating tank is 6 to 12 hours;

[0058] (2) In mixed reaction tank 2, the wastewater reacts with NaOH and CaCl2. The hydraulic retention time of mixed reaction tank 2 is 3-5 minutes, and the pH is 9-12. The molar ratio of calcium ions in the calcium salt added to the mixed reaction tank to fluoride ions in the wastewater is 0.6-0.8. After the reaction is completed, it enters coagulation reaction tank 3 and flocculation reaction tank 4 in sequence. The hydraulic retention time of coagulation reaction tank 3 is 3-5 minutes. The dosage of coagulant polyaluminum chloride (PAC) is 100-300 mg / L, and the hydraulic retention time of flocculation reaction tank 4 is 3-5 minutes. The dosage of flocculant anionic polyacrylamide (PAM) is 1-5 mg / L.

[0059] (3) After coagulation and flocculation, the wastewater enters the sedimentation tank 5 for sedimentation separation. The supernatant of the sedimentation separation enters the phosphorus recovery tank 6. The sludge part is returned to the flocculation reaction tank 4, and the remaining sludge is discharged to the physical and chemical sludge treatment unit. The return ratio of the sludge return from the sedimentation tank is 20~50%; the surface load of the sedimentation tank 5 is 5~10 m 3 / (m 2 ·h), and the hydraulic retention time is 10~30 min.

[0060] Through the above steps, it is detected that the concentration of fluoride ions in the wastewater entering the phosphorus recovery tank 6 is reduced to below 10 mg / L.

[0061] (4) The pH of the wastewater entering the phosphorus recovery tank 6 is 9-12. The unreacted fluoride ions in the wastewater react with the newly added CaCl2 precipitant to form calcium fluoride sludge; the phosphorus ions in the wastewater react with CaCl2 under alkaline conditions to form calcium phosphate sludge. After solid-liquid separation, part of the sludge is returned to the sludge return pipeline of the sedimentation tank 5, and the remaining part is discharged to the phosphorus product recovery unit to recover phosphorus. The reflux ratio is 10-20%. The molar ratio of Ca ions in the calcium chloride agent added to the phosphorus recovery tank 6 to phosphate ions in the wastewater is 3-5; the supernatant of the sedimentation separation flows by gravity into the mixing buffer tank 7. The fluoride ion concentration in the supernatant is detected to be below 1.5 mg / L, and the phosphate concentration is detected to be below 0.3 mg / L.

[0062] (5) The wastewater entering the mixing buffer tank 7 is adjusted with H2SO4 to adjust the pH value and then enters the hydrolysis acidification tank 8. The hydraulic retention time of the mixing reaction tank is 3~5min, and the pH value of the effluent from the mixing reaction tank is 6~9;

[0063] (6) The wastewater entering the hydrolysis and acidification tank 8 is pumped into the water phase enrichment cyclone 14, and the rest is filtered through the membrane grid 9 and then enters the anoxic tank 10, the aerobic tank 11, and the MBR membrane tank 12 in sequence. The amount of acidified water entering the water phase enrichment cyclone 14 accounts for 20% to 50% of the total water inlet of the hydrolysis and acidification tank. The hydraulic retention time of the hydrolysis and acidification tank is 6h to 12h; the water produced by the MBR membrane tank 12 is discharged, and the concentrated water enters the recirculation tank 13;

[0064] (7) The effluent from the recirculation tank 13 is pumped into the sludge phase enrichment cyclone 16. The light fraction overflowing from the top of the sludge phase enrichment cyclone is discharged to the biological sludge treatment system, and the heavy fraction at the bottom flows by gravity into the biological phosphorus release tank 15. The hydraulic retention time of the biological phosphorus release tank is 1~5h, and the ORP value is ≤-250mV. The effluent from the biological phosphorus release tank 15 is pumped together with the effluent from the hydrolysis and acidification tank into the liquid phase enrichment cyclone 14. The light fraction separated by the water phase enrichment cyclone 14 is returned to the anoxic tank 10, and the heavy fraction enters the phosphorus recovery tank 6 together with the effluent from the sedimentation tank. The separation pressure of the sludge phase enrichment cyclone 16 and the water phase enrichment cyclone 14 is 0.1~0.4 MPa.

[0065] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also within the scope of protection of the present invention.

Claims

1. A semiconductor industry fluorine-containing wastewater treatment system, characterized in that: include: Regulating unit, used to balance the influent water quality and quantity; The pretreatment unit is used to add chemical agents to the conditioned wastewater to cause fluoride ions to form precipitation with the precipitant, and then discharge it from the system in the form of physical and chemical sludge after solid-liquid separation to achieve fluoride removal; The phosphorus recovery unit is used to add a precipitant to the pretreated wastewater to form calcium phosphate precipitates. After solid-liquid separation, the precipitates are discharged from the system in the form of physicochemical sludge, thereby achieving further fluoride removal and phosphorus recovery. Biochemical treatment and membrane separation unit, used to remove organic matter from wastewater after phosphorus recovery through microbial degradation and membrane separation; as well as The phosphorus release and calcium removal unit is used to release phosphorus from the membrane separation concentrated water and enter the phosphorus recovery unit together with the partially hydrolyzed acidified water from the biochemical treatment and membrane separation units after cyclone enrichment, so that the calcium fluoride and calcium phosphate remaining in the biochemical system are removed from the system in the form of physical and chemical sludge discharge; The phosphorus release and decalcification unit includes a reflow tank (13), a mud phase enrichment cyclone (16), a biological phosphorus release tank (15) and a water phase enrichment cyclone (14); the membrane separation concentrated water enters the reflow tank (13), is pumped to the mud phase enrichment cyclone (16) for centrifugal separation, the separated light components are discharged as biological sludge, and the heavy components enter the biological phosphorus release tank (15); the mud water in the biological phosphorus release tank (15) is pumped together with the partially hydrolyzed acidified water of the biochemical treatment and membrane separation unit to the water phase enrichment cyclone (14) for centrifugal separation, the separated light components enter the anoxic tank of the biochemical treatment and membrane separation unit, and the heavy components enter the phosphorus recovery unit together with the effluent of the pretreatment unit; The biochemical treatment and membrane separation unit includes a hydrolysis and acidification tank (8), an anoxic tank (10), an aerobic tank (11) and an MBR membrane tank (12) connected in sequence; part of the effluent from the hydrolysis and acidification tank (8) is pumped into the phosphorus release unit and enters the phosphorus recovery unit together with the wastewater from the phosphorus release unit to recover phosphorus.

2. A semiconductor industry fluorine-containing wastewater treatment system according to claim 1, characterized in that: The regulating unit comprises a regulating tank (1), the bottom of which is provided with a first aeration device, which is connected to the biochemical aeration main pipe of the biochemical treatment and membrane separation unit.

3. A semiconductor industry fluorine-containing wastewater treatment system according to claim 1, characterized in that: The pretreatment unit comprises a mixing reaction tank (2), a coagulation reaction tank (3), a flocculation reaction tank (4) and a sedimentation tank (5) which are connected in sequence. Part of the sludge in the sedimentation tank is discharged, and part of it is returned to the flocculation reaction tank (4).

4. A semiconductor industry fluorine-containing wastewater treatment system according to claim 3, characterized in that: The mixing reaction tank (2) is provided with an alkali solution and precipitant dosing device, and the bottom of the coagulation reaction tank (3) is provided with a second aeration device, which is connected to the membrane scrubbing aeration main pipe of the biochemical treatment and membrane separation unit.

5. The semiconductor industry fluorine-containing wastewater treatment system according to claim 1, characterized in that: The phosphorus recovery unit comprises a phosphorus recovery tank (6) and a mixing buffer tank (7). A precipitant dosing device is provided in the phosphorus recovery tank (6). After solid-liquid separation in the phosphorus recovery tank, the precipitated sludge is partially discharged to recover phosphorus, and the remaining portion is combined with the sludge in the sedimentation tank of the pretreatment unit; the supernatant of the sedimentation separation enters the mixing buffer tank (7).

6. A semiconductor industry fluorine-containing wastewater treatment system according to claim 5, characterized in that: A sulfuric acid dosing device and a stirrer are provided in the mixing buffer tank (7).

7. The semiconductor industry fluorine-containing wastewater treatment system according to claim 1, characterized in that: A domestic sewage inlet pipe is provided in the hydrolysis and acidification tank (8).

8. A method for treating fluorine-containing wastewater in semiconductor industry using the system according to any one of claims 1 to 7, characterized in that: The steps include: (1) After the fluorine-containing wastewater is regulated in water quality and quantity by the regulating unit, it enters the pretreatment unit; (2) In the pretreatment unit, the wastewater is first mixed with NaOH and CaCl2, and then subjected to coagulation and flocculation followed by sedimentation separation. During this process, fluoride ions form calcium fluoride sludge, which is discharged in the form of physical and chemical sludge. The supernatant of sedimentation separation enters the phosphorus recovery unit; (3) In the phosphorus recovery unit, fluoride ions are further removed by adding CaCl2 precipitant to the wastewater, and the phosphorus ions in the wastewater react with CaCl2 to form calcium phosphate precipitates. After solid-liquid separation, phosphorus is recovered and the calcium fluoride sludge is discharged as physical and chemical sludge. The supernatant of the sedimentation separation is adjusted with H2SO4 for pH value and then enters the biochemical treatment and membrane separation unit; (4) In the biochemical treatment and membrane separation unit, the wastewater undergoes hydrolysis and acidification, anoxic treatment, and aerobic treatment in sequence, and then passes through the MBR membrane to separate organic matter, harmful substances, and salts, and is discharged in compliance with the standards; the membrane separation concentrated water enters the phosphorus release unit; (5) In the phosphorus release and calcium removal unit, the calcium fluoride and calcium phosphate remaining in the biochemical system are enriched by using a mud phase enrichment cyclone and then sent to the biological phosphorus release pool. The biological phosphorus release pool releases the phosphorus in the mud water, which is then combined with the partially hydrolyzed acidified water from the biochemical treatment and membrane separation units and then enriched by the water phase enrichment cyclone before entering the phosphorus recovery unit.

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