Lithium iron phosphate wastewater treatment process

Abstract

The invention relates to the technical field of lithium iron phosphate wastewater treatment, in particular to a lithium iron phosphate wastewater treatment process. According to the device, equipment cleaning water is pretreated through filtration, meanwhile, tail gas absorption water can be pretreated through electrolytic catalytic oxidation and nano air floatation so as to improve the biodegradability of the tail gas absorption water, and then the pretreated equipment cleaning water and tail gas absorption water are mixed and subjected to multi-stage biochemical treatment and filtration; and meanwhile, the equipment cleaning water and the tail gas absorption water are mixed after being pretreated so as to synchronously perform biochemical treatment and filtration, so that the wastewater treatment flow is effectively shortened, and the wastewater treatment efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of lithium iron phosphate wastewater treatment, and in particular to a lithium iron phosphate wastewater treatment process. Background Art

[0002] During the production process of lithium iron phosphate, the mill needs to be regularly inspected and cleaned. The wastewater after cleaning the equipment will contain suspended matter such as iron phosphate, lithium carbonate and glucose. At the same time, the absorption of the calcination tail gas will produce calcination tail gas absorption water containing tar, COD, suspended matter and other pollutants. These equipment cleaning wastewater and calcination tail gas absorption water need to be purified before they can be discharged.

[0003] During the production process of lithium iron phosphate, the mill needs to be regularly inspected and cleaned. The wastewater after cleaning the equipment will contain suspended matter such as iron phosphate, lithium carbonate and glucose. At the same time, the absorption of the calcination tail gas will produce calcination tail gas absorption water containing tar, COD, suspended matter and other pollutants. These equipment cleaning wastewater and calcination tail gas absorption water need to be purified before they can be discharged.

[0004] The Chinese invention patent with patent number 202310420894.9 records a method and system for recycling and treating lithium iron phosphate cleaning wastewater. The patent uses coagulation and sedimentation pre-treatment, and uses ferrous sulfate and flocculants to flocculate and precipitate SS in the wastewater under alkaline conditions. The excess ferrous sulfate spontaneously precipitates in the alkaline pH environment in the sedimentation tank to reduce the SS in the water quality; the precipitated sludge and water are separated and recovered, and the supernatant is added to adjust the pH and enter the biochemical system to fully degrade impurities such as COD and ammonia nitrogen, and then filtered and desalinated with RO pure water before entering the circulation system. The pretreatment process of this patent is long and the precipitation effect is poor.

[0005] As for the absorption water of calcination tail gas, the Chinese invention patent with patent number 202210798532.9 records a lithium iron phosphate production wastewater treatment system, which includes a wastewater collection tank, a first primary reaction tank, a second primary reaction tank, a first sedimentation tank, a first secondary reaction tank, a second secondary reaction tank, a secondary sedimentation tank, a pH adjustment tank, a biochemical system, and a discharge monitoring tank connected in sequence. The sludge discharge port of the first sedimentation tank, the second sedimentation tank, and the integrated MBR wastewater treatment device are all connected to the sludge tank through a pipeline. The deficiency of this patent is that the problem of lithium iron phosphate wastewater containing tar and being difficult to biodegrade cannot be solved by only using a pretreatment system that sequentially adds Ca2+ / PAC / PAM and Fe3+ / PAC / PAM in a two-stage reaction precipitation, and the biochemical effect of the subsequent A / A / O / MBR biochemical system is affected. The present invention provides a new solution based on the characteristics of equipment cleaning water and tail gas absorption water generated in the production of lithium iron phosphate and the deficiencies of existing related patents. Summary of the invention

[0006] The purpose of the present invention is to provide a lithium iron phosphate wastewater treatment process to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a lithium iron phosphate wastewater treatment process, characterized in that it comprises the following steps: 1) Equipment cleaning water pretreatment: Equipment cleaning water is filtered through a polytetrafluoroethylene filter; 2) Tail gas absorption water pretreatment: The tail gas absorption water undergoes electrolytic catalytic oxidation and nano-flotation to improve the biodegradability of the wastewater and remove some of the difficult-to-degrade pollutants in the wastewater; 3) High-efficiency biochemical treatment of pretreated mixed water: The effluent from the equipment cleaning water pretreatment and the effluent from the tail gas absorption water pretreatment are mixed and then subjected to multi-stage biochemical treatment and filtration through hydrolysis acidification, high-efficiency anaerobic, aerobic biochemical, and membrane bioreactor, and the treated effluent meets the discharge standards.

[0008] Furthermore, the filtration accuracy of the polytetrafluoroethylene filter is 0.1 μm.

[0009] Furthermore, in step 2), the tar in the tail gas absorption water is electrolyzed and catalytically oxidized by electrolytic catalytic oxidation, and the organic matter such as phenol, aniline, pyridine, naphthalene and the like which are difficult to biodegrade in the tar is decomposed, and the B / C ratio of the tail gas absorption water is increased to greater than 0.3, and then the micron and nanometer-scale tiny bubbles generated by nano-flotation are used to form scum to discharge the fine particles and oil in the wastewater, and the electrolytic catalytic oxidation products of the tail gas absorption water are collected.

[0010] Furthermore, in step 3), the pre-treated mixed water is hydrolyzed and acidified in a hydrolysis acidification tank, and the benzene and naphthalene organic pollutants in the wastewater are opened and broken to further improve the biodegradability of the wastewater. Then, an anaerobic biochemical treatment is carried out in a high-efficiency anaerobic reactor, and an anaerobic circulation pump is used to maintain the inlet rising flow rate of the high-efficiency anaerobic reactor at ≥0.5m / H, which can avoid anaerobic sludge precipitation and is conducive to the formation of anaerobic granular sludge, thereby improving the biochemical treatment effect of the high-efficiency anaerobic reactor. Then, an aerobic biochemical treatment is carried out in an aerobic biochemical tank to further reduce the COD of the wastewater. Finally, a high-efficiency aerobic biochemical treatment is carried out in a membrane bioreactor with a high concentration of 8000 to 20000 mg / L of aerobic sludge, and membrane filtration is used to reduce the COD of the treated effluent to ≤50mg / L and the suspended solids to ≤5mg / L, so that the effluent meets the discharge standards.

[0011] In summary, the technical effects and advantages of the present invention are as follows: In the present invention, the equipment cleaning water is pretreated by the provided filtration, and the tail gas absorption water can be pretreated by electrolytic catalytic oxidation and nano-flotation to improve its biodegradability, and then the pretreated equipment cleaning water and tail gas absorption water are mixed and subjected to multi-stage biochemical treatment and filtration, thereby effectively improving the purification effect of the wastewater, and at the same time, the equipment cleaning water and tail gas absorption water are mixed after being pretreated to simultaneously perform biochemical treatment and filtration, thereby effectively shortening the wastewater treatment process and improving the efficiency of wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0013] Figure 1 A schematic diagram of the system structure of a lithium iron phosphate wastewater treatment device in an embodiment of the present invention. In the figure: 1. Equipment cleaning pool; 21. Filter pump; 22. Polytetrafluoroethylene filter; 23. Filter water tank; 231. Filter water pump; 31. Filter collection box; 32. Filter pressure pump; 33. Filter dehydration system; 4. Intermediate pool; 5. Tail gas absorption pool; 51. Pretreatment lifting pump; 6. Electrolytic catalytic oxidation system; 71. Nano gas flotation tank; 72. Scum collection tank; 73. Scum pressure pump Pump; 74, scum dehydration system; 81, hydrolysis acidification tank; 82, high-efficiency anaerobic reactor; 83, biochemical lifting pump; 831, anaerobic circulation pump; 84, anaerobic lifting pump; 85, membrane bioreactor; 851, membrane suction pump; 852, membrane scrubbing fan; 86, aerobic biochemical tank; 87, aerobic aeration fan; 88, treatment water tank; 881, drainage pump; 9, filter backwash pump; 10, membrane backwash pump. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] Please refer to Figure 1A lithium iron phosphate wastewater treatment device shown includes an equipment cleaning water pool 1, the water outlet of the equipment cleaning water pool 1 is connected to a filtering device for filtering and separating equipment cleaning water, the mud discharge port of the filtering device is connected to a sludge treatment device, the water outlet of the sludge treatment device is connected to an intermediate water pool 4, and the water outlet of the sludge treatment device is connected to the second water inlet of the intermediate water pool 4; It also includes a tail gas absorption water pool 5, the water outlet of the tail gas absorption water pool 5 is connected to an electrolytic catalytic oxidation system 6 for treating tail gas absorption water, the water outlet of the electrolytic catalytic oxidation system 6 is connected to a scum treatment device, the scum treatment device includes a scum outlet, the water outlet of the scum treatment device is connected to an intermediate water pool 4, and the water outlet of the scum treatment device is connected to a first water inlet of the intermediate water pool 4; The water outlet of the intermediate water tank 4 is connected to a multi-stage biochemical treatment device, the water outlet of the multi-stage biochemical treatment device is connected to a membrane bioreactor 85, the water outlet of the membrane bioreactor 85 is connected to a membrane suction pump 851, and the water outlet of the membrane suction pump 851 is connected to a treatment water outlet tank 88.

[0016] Preferably, the filtering device includes a filtering pump 21 connected to the water outlet of the equipment cleaning water tank 1, the water outlet of the filtering pump 21 is connected to a polytetrafluoroethylene filter 22, the water outlet of the polytetrafluoroethylene filter 22 is connected to a filtering water tank 23, the mud discharge port of the polytetrafluoroethylene filter 22 is connected to the sludge treatment device, and the water outlet of the filtering water tank 23 is connected to the second water inlet of the intermediate water tank 4.

[0017] Preferably, the sludge treatment device includes a filtrate collecting box 31, the filtrate collecting box 31 has a filtrate dewatering system 33 connected to its filtrate pressure pump 32, the water outlet of the filtrate dewatering system 33 is connected to the second water inlet of the equipment cleaning pool 1, and the filtrate dewatering system 33 is provided with a filtrate outlet.

[0018] Preferably, the scum treatment device includes a solid-liquid separation device, the water inlet of the solid-liquid separation device is connected to the water outlet of the electrolytic catalytic oxidation system 6, the slag outlet of the solid-liquid separation device is connected to a slag collection tank 72, the slag outlet of the slag collection tank 72 is connected to a slag dehydration system 74 through a slag pressure pump 73, the water outlet of the slag dehydration system 74 is connected to the second water inlet of the tail gas absorption tank 5, and the slag dehydration system 74 includes a slag outlet.

[0019] Preferably, the solid-liquid separation device is a nanometer air flotation pool 71 , and the water outlet of the nanometer air flotation pool 71 is connected to the first water inlet of the intermediate water pool 4 .

[0020] Preferably, the multi-stage biochemical treatment device includes a hydrolysis and acidification tank 81 and a high-efficiency anaerobic reactor 82, the water outlet of the intermediate water tank 4 is connected to the water inlet of the hydrolysis and acidification tank 81 through a biochemical lifting pump 83, the water outlet of the hydrolysis and acidification tank 81 is connected to the water inlet of the high-efficiency anaerobic reactor 82 through an anaerobic lifting pump 84, and the water outlet of the high-efficiency anaerobic reactor 82 is connected to the water inlet of the membrane bioreactor 85.

[0021] Preferably, an anaerobic circulation pump 831 is also installed on the high-efficiency anaerobic reactor 82 , the liquid inlet of the anaerobic circulation pump 831 is connected to the circulating liquid outlet of the high-efficiency anaerobic reactor 82 , and the water outlet of the anaerobic circulation pump 831 is connected to the water inlet of the high-efficiency anaerobic reactor 82 .

[0022] Preferably, the multi-stage biochemical treatment device further includes an aerobic biochemical pool 86, the water outlet of the high-efficiency anaerobic reactor 82 is connected to the first water inlet of the aerobic biochemical pool 86, the water outlet of the aerobic biochemical pool 86 is connected to the water inlet of the membrane bioreactor 85, and the aerobic biochemical pool 86 further includes an aerobic aeration fan 87, and the air outlet of the aerobic aeration fan 87 is connected to the air inlet of the aerobic biochemical pool 86.

[0023] Preferably, the polytetrafluoroethylene filter 22 is connected to a filter backwash pump 9 , and the membrane bioreactor 85 is connected to a membrane backwash pump 10 .

[0024] Preferably, the water inlet of the filter backwash pump 9 is connected to the water outlet of the filter water tank 23 , and the water inlet of the membrane backwash pump 10 is connected to the water outlet of the treatment water tank 88 .

[0025] The equipment cleaning water is connected to the first water inlet of the equipment cleaning water pool 1, the water outlet of the equipment cleaning water pool 1 is connected to the water inlet of the polytetrafluoroethylene filter 22 through the filter pump 21, and the mud outlet of the polytetrafluoroethylene filter 22 is connected to the mud inlet of the filtered material collection box 31; Preferably, the filtration accuracy of the polytetrafluoroethylene filter 22 is 0.1 μm, which can effectively intercept the iron phosphate and lithium carbonate in the recovered water, thereby filtering the suspended solids content of the equipment cleaning water from 500 to 1500 mg / L to less than 5 mg / L. The filtrate is filtered by a plate and frame filter press, which can effectively recover the iron phosphate and lithium carbonate in the equipment cleaning water. The recovery rate of iron phosphate and lithium carbonate is greater than 99%, saving phosphorus and lithium resources. The mud outlet of the filter collecting box 31 in the sludge treatment device is connected to the mud inlet of the filter dehydration system 33 through the filter pressure pump 32, the water outlet of the filter dehydration system 33 is connected to the second water inlet of the equipment cleaning pool 1, the mud outlet of the filter dehydration system 33 sends out the filter cake for recovery, and the water outlet of the polytetrafluoroethylene filter 22 is connected to the water inlet of the filter water tank 23; The water outlet of the filter water tank 23 is connected to the backwash water inlet of the polytetrafluoroethylene filter 22 through the filter backwash pump 9, and the water outlet of the filter water tank 23 is connected to the second water inlet of the intermediate water tank 4 through the filter water pump 231; The tail gas absorption water is connected to the first water inlet of the tail gas absorption water pool 5, the water outlet of the tail gas absorption water pool 5 is connected to the water inlet of the electrolytic catalytic oxidation system 6 through the pretreatment booster pump 51, and the water outlet of the electrolytic catalytic oxidation system 6 is connected to the water inlet of the nano-gas flotation tank 71; For the tail gas absorption water containing multiple pollutants such as tar and suspended solids, electrolytic catalytic oxidation can be used to electrolyze and catalytically oxidize the tar in the tail gas absorption water, decompose the organic matter such as phenol, aniline, pyridine, naphthalene and other organic substances that are difficult to biodegrade in the tar, and increase the B / C ratio of the tail gas absorption water from less than 0.1 to more than 0.3; The slag outlet of the nano-gas flotation tank 71 is connected to the slag inlet of the slag collection tank 72, and the slag outlet of the slag collection tank 72 is connected to the slag inlet of the slag dehydration system 74 through the slag pressure pump 73. The water outlet of the slag dehydration system 74 is connected to the second water inlet of the tail gas absorption water tank 5, and the slag outlet of the slag dehydration system 74 sends the slag out for transportation; The nano-flotation tank 71 can remove more than 50% of the difficult-to-degrade pollutants in the wastewater, and reduce the content of tail gas absorption water from 5000-15000 mg / L to 3000-10000 mg / L, thereby improving the biodegradability of the tail gas absorption wastewater; The water outlet of the nanometer air flotation tank 71 is connected to the first water inlet of the intermediate water tank 4, the water outlet of the intermediate water tank 4 is connected to the water inlet of the hydrolysis acidification tank 81 through the biochemical lifting pump 83, the water outlet of the hydrolysis acidification tank 81 is connected to the water inlet of the high-efficiency anaerobic reactor 82 through the anaerobic lifting pump 84, the circulating liquid outlet of the high-efficiency anaerobic reactor 82 is also connected to the water inlet of the high-efficiency anaerobic reactor 82 through the anaerobic circulating pump 831, the water outlet of the high-efficiency anaerobic reactor 82 is connected to the first water inlet of the aerobic biochemical tank 86, and the air outlet of the aerobic aeration fan 87 is connected to the air inlet of the aerobic biochemical tank 86; The hydrolysis acidification tank 81 can hydrolyze and acidify the wastewater, open the ring and break the chain of benzene and naphthalene organic pollutants in the wastewater, further improve the biodegradability of the wastewater, and then pass through the high-efficiency anaerobic reactor 82 for anaerobic biochemical treatment. Under the action of the anaerobic circulation pump 831, the water inlet flow rate of the high-efficiency anaerobic reactor 82 can be increased to ≥0.5m / H, which can avoid the precipitation of anaerobic sludge and is conducive to the formation of anaerobic granular sludge, further improving the biochemical treatment effect of the high-efficiency anaerobic reactor 82, and the removal rate reaches 40-60%; The water outlet of the aerobic biochemical tank 86 is connected to the water inlet of the membrane bioreactor 85, the air outlet of the membrane scrubbing fan 852 is connected to the air inlet of the membrane bioreactor 85, the water outlet of the membrane bioreactor 85 is connected to the water inlet of the treatment water outlet tank 88 through the membrane suction pump 851, the water outlet of the treatment water outlet tank 88 is connected to the backwash water inlet of the membrane bioreactor 85 through the membrane backwash pump 10, the backwash water outlet of the membrane bioreactor 85 is connected to the second water inlet of the aerobic biochemical tank 86, and the water outlet of the treatment water outlet tank 88 also sends out qualified discharge water through the drainage pump 881.

[0026] The lithium iron phosphate wastewater treatment process includes the following steps.

[0027] Equipment cleaning water pretreatment: Equipment cleaning water is filtered through a polytetrafluoroethylene filter 22 with a filtration accuracy of 0.1 μm to effectively intercept and recover iron phosphate and lithium carbonate in the water; Specifically, the equipment cleaning water is filtered using a polytetrafluoroethylene filter 22 with a filtration accuracy of 0.1 μm, effectively intercepting the filtrate in the equipment cleaning water. The suspended solids content of the pretreated effluent from the equipment cleaning water is less than 5 mg / L. The sludge discharged from the polytetrafluoroethylene filter 22 is pressed out of the filter cake and recovered through the filtrate dehydration system 33, and more than 99% of the iron phosphate and lithium carbonate in the equipment cleaning water are recovered.

[0028] Tail gas absorption water pretreatment: Tail gas absorption water undergoes electrolytic catalytic oxidation and nano-flotation to improve the biodegradability of wastewater and remove some difficult-to-degrade pollutants in the wastewater; Specifically, the tar in the exhaust gas absorption water is first electrolyzed and catalytically oxidized by electrolytic catalytic oxidation, and the organic matter such as phenol, aniline, pyridine, naphthalene and other organic substances that are difficult to biodegrade in the tar are decomposed, and the B / C ratio of the exhaust gas absorption water is increased to greater than 0.3. Then, the micron and nanometer-level tiny bubbles generated by nano-flotation are used to form scum to discharge the fine particles and oil in the wastewater, and the electrolytic catalytic oxidation products of the exhaust gas absorption water are collected, and the scum is pressed out and transported out through the scum dehydration system 74, thereby effectively improving the biodegradability of the wastewater and removing more than 50% of the difficult-to-degrade pollutants in the wastewater.

[0029] Pretreatment mixed water high-efficiency biochemical treatment: The pretreatment effluent of equipment cleaning water and the pretreatment effluent of tail gas absorption water are mixed and then subjected to multi-stage biochemical treatment and filtration by hydrolysis acidification, high-efficiency anaerobic, aerobic biochemical, and membrane bioreactor 85, and the treated effluent meets the discharge standards; Specifically, the pre-treated mixed water is firstly hydrolyzed and acidified by the hydrolysis acidification tank 81, and the benzene and naphthalene organic pollutants in the wastewater are opened and broken to further improve the biodegradability of the wastewater. Then, the anaerobic biochemical treatment is carried out by the high-efficiency anaerobic reactor. The anaerobic circulation pump 831 is used to maintain the inlet rising flow rate of the high-efficiency anaerobic reactor 82 ≥ 0.5m / H, which can avoid the precipitation of anaerobic sludge and is conducive to the formation of anaerobic granular sludge, thereby improving the biochemical treatment effect of the high-efficiency anaerobic reactor 82, and the COD removal rate reaches 50-80%. Then, the aerobic biochemical treatment is carried out by the aerobic biochemical tank 86 to further reduce the COD of the wastewater. Finally, the high-concentration aerobic sludge of 8000-20000mg / L in the membrane bioreactor 85 is used for high-efficiency aerobic biochemical treatment, and the membrane filtration is used to reduce the COD of the treated effluent to ≤ 50mg / L and the suspended solids to ≤ 5mg / L, so that the effluent meets the discharge standards.

[0030] Working principle: the equipment cleaning water is filtered through a polytetrafluoroethylene filter 22 with a filtration accuracy of 0.1μm, effectively intercepting iron phosphate and lithium carbonate in the recovered water, and then the sludge discharge port of the polytetrafluoroethylene filter 22 sends the sludge generated by the filtration interception into the filter collection box 31, and the water outlet of the polytetrafluoroethylene filter 22 sends the wastewater generated by the filtration into the filter water tank 23, and then the filtered water in the filter water tank 23 is sent to the intermediate water tank 4 by the filter water pump 231, and then the sludge in the filter collection box 31 is sent to the filter dehydration system 33 by the filter pressure pump 32 for dehydration, and the dehydrated wastewater is sent to the equipment cleaning water tank 1, so that the pretreatment of the equipment cleaning water can be completed.

[0031] The tail gas absorption water is subjected to electrolytic catalytic oxidation and nano-flotation to improve the biodegradability of the wastewater and remove some of the difficult-to-degrade pollutants in the wastewater. Then the wastewater produced in the nano-flotation tank 71 is sent to the intermediate water tank 4, and the scum produced in the nano-flotation tank 71 is sent to the scum collection tank 72. Then the scum in the scum collection tank 72 is sent to the scum dehydration system 74, and the water removed from the scum dehydration system 74 is sent to the tail gas absorption water tank 5. The dehydrated scum in the scum dehydration system 74 is sent out, thus completing the pretreatment of the tail gas absorption water.

[0032] Subsequently, the mixed water of the equipment cleaning water pretreatment effluent and the tail gas absorption water pretreatment effluent in the intermediate water tank 4 is sent to the hydrolysis acidification tank 81, the high-efficiency anaerobic reactor 82, the aerobic biochemical tank 86 and the membrane bioreactor 85 for biochemical treatment and filtration to obtain the treated water that meets the discharge standards after purification, and then the purified treated water is sent to the treated water tank 88, and the lithium iron phosphate wastewater treatment is completed.

[0033] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A lithium iron phosphate wastewater treatment process, characterized in that: The following steps are involved: 1) Equipment cleaning water pretreatment: Equipment cleaning water is filtered through a polytetrafluoroethylene filter; 2) Tail gas absorption water pretreatment: The tail gas absorption water is subjected to electrolytic catalytic oxidation and nano-flotation to improve the biodegradability of the wastewater and remove some of the difficult-to-degrade pollutants in the wastewater; 3) High-efficiency biochemical treatment of pretreated mixed water: The effluent from the equipment cleaning water pretreatment and the effluent from the tail gas absorption water pretreatment are mixed and then subjected to multi-stage biochemical treatment and filtration through hydrolysis acidification, high-efficiency anaerobic, aerobic biochemical, and membrane bioreactor, and the treated effluent meets the discharge standards.

2. A lithium iron phosphate wastewater treatment process according to claim 1, characterized in that: The filtration accuracy of the PTFE filter is 0.1 μm.

3. A lithium iron phosphate wastewater treatment process according to claim 1, characterized in that: In step 2), the tar in the tail gas absorption water is electrolyzed and catalytically oxidized by electrolytic catalytic oxidation, and the organic matter such as phenol, aniline, pyridine, naphthalene and the like which are difficult to biodegrade in the tar is decomposed, and the B / C ratio of the tail gas absorption water is increased to greater than 0.3, and then the micron and nanometer-scale tiny bubbles generated by nano-flotation are used to form scum to discharge the fine particles and oil in the wastewater, and the electrolytic catalytic oxidation products of the tail gas absorption water are collected.

4. A lithium iron phosphate wastewater treatment process according to claim 1, characterized in that: In step 3), the pre-treated mixed water is hydrolyzed and acidified in a hydrolysis acidification tank, and the benzene and naphthalene organic pollutants in the wastewater are opened and broken to further improve the biodegradability of the wastewater. Then, an anaerobic biochemical treatment is carried out in a high-efficiency anaerobic reactor, and an anaerobic circulation pump is used to maintain the inlet rising flow rate of the high-efficiency anaerobic reactor at ≥0.5m / H, which can avoid anaerobic sludge precipitation and is conducive to the formation of anaerobic granular sludge, thereby improving the biochemical treatment effect of the high-efficiency anaerobic reactor. Then, an aerobic biochemical treatment is carried out in an aerobic biochemical tank to further reduce the COD of the wastewater. Finally, a high-efficiency aerobic biochemical treatment is carried out in a membrane bioreactor with a high concentration of 8000 to 20000 mg / L of aerobic sludge, and membrane filtration is used to reduce the COD of the treated effluent to ≤50mg / L and the suspended solids to ≤5mg / L, so that the effluent meets the discharge standards.

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