A method for resource-based treatment of phosphorus-containing wastewater

Abstract

The present invention relates to the field of wastewater treatment technology and discloses a method for resource-recovery treatment of phosphorus-containing wastewater. The method comprises the following steps: 1) subjecting the phosphorus-containing wastewater to membrane concentration until the organic phosphorus in the membrane concentrate is in solid form, thereby obtaining a concentrated solution a containing solid organic phosphorus and a permeate a; 2) subjecting the membrane concentrate obtained in step 1) to membrane separation to obtain a concentrated solution b containing solid organic phosphorus and a permeate b containing salt, and evaporating and crystallizing the permeate b containing salt to obtain industrial salt; 3) filtering the concentrated solution b containing solid organic phosphorus to obtain a filtered concentrate and a filtered clear solution containing solid organic phosphorus, and drying the filtered concentrate containing solid organic phosphorus to obtain solid organic phosphorus. The present method for treating phosphorus-containing wastewater can recover organic phosphorus simultaneously with inorganic salts. The process is simple and easy to control, thereby improving resource utilization and reducing wastewater treatment costs for enterprises.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment and relates to a method for resource-based treatment of phosphorus-containing wastewater. Background Art

[0002] In recent years, phosphorus-based flame retardants, with their advantages such as low corrosivity and low toxicity, have become an important alternative to brominated flame retardants, with broad market application prospects. Among them, aluminum diethylphosphinate is the most representative of alkylphosphinate flame retardants. It has advantages such as small particle size, high whiteness, good thermal stability, and non-toxicity. It is widely used in flame retardant products such as thermoplastics, thermosets, fibers, and textiles.

[0003] The production of aluminum diethylphosphinate (ADP) generates a large amount of refractory organic wastewater characterized by high COD concentrations and total phosphorus content, with ADP being the primary component. Existing treatment methods, including oxidation, precipitation, extraction, and biochemical treatment, can render the total phosphorus harmless enough for discharge and further treat the inorganic salts in the wastewater for resource reuse. However, organic phosphorus cannot be recovered, resulting in a waste of resources (ADP).

[0004] The invention patent, publication number CN 108609788A, discloses a process for treating phosphorus-based flame retardant wastewater, comprising the following steps: (1) adjusting the pH of the phosphorus-based flame retardant wastewater to 2-9, adding a soluble trivalent iron salt, stirring, and filtering to obtain filtrate I; (2) neutralizing and flocculating filtrate I, separating and removing the precipitate to obtain filtrate II; and (3) evaporating, concentrating, crystallizing, and desalting filtrate II. The evaporated condensate is directly discharged or recycled, and the concentrated liquid is directly returned to step (1) for repeated treatment. The treatment process of the present invention is suitable for the continuous treatment of phosphorus-based flame retardant wastewater. It is based on the main process of dosing pretreatment, neutralization and flocculation, and evaporation and condensation. It is simple to operate, low-cost, and can achieve zero discharge of phosphorus-based flame retardant wastewater.

[0005] The invention patent with publication number CN 108975585 A discloses a method for resource-based treatment of phosphorus-containing flame retardant production wastewater. The method comprises the following steps: (1) wet catalytic oxidation: subjecting the phosphorus-containing flame retardant production wastewater to wet catalytic oxidation treatment to obtain an oxidation liquid; (2) membrane separation: subjecting the oxidation liquid obtained in step (1) to membrane separation to obtain a membrane concentrate and a membrane permeate; (3) crystallization: subjecting the membrane concentrate obtained in step (2) to freeze crystallization to obtain industrial phosphate; and subjecting the membrane permeate obtained in step (2) to evaporation and crystallization for desalination. The method of the present invention mainly utilizes wet catalytic oxidation, combined with membrane separation and crystallization processes to treat phosphorus-containing flame retardant wastewater. The process is simple, can effectively degrade organic phosphorus in the wastewater, and can resource-recover salt in the wastewater, achieving the goal of zero discharge.

[0006] The above patented technical solutions all achieve the discharge of organophosphorus wastewater in compliance with the discharge standards and recover inorganic salts as resources, but do not recover organophosphorus, resulting in a waste of organophosphorus resources. Summary of the Invention

[0007] The present invention solves the problem that organic phosphorus in phosphorus-containing wastewater cannot be recovered, resulting in waste of organic phosphorus, and provides a method for resource-based treatment of phosphorus-containing wastewater. The method can recover organic phosphorus while recovering inorganic salts. The process is simple and easy to control, thereby improving resource utilization and reducing the wastewater treatment cost of enterprises.

[0008] To achieve the purpose of the invention, the present invention adopts the following technical solution: a method for resource-based treatment of phosphorus-containing wastewater, comprising the following steps:

[0009] 1) Performing membrane concentration treatment on the phosphorus-containing wastewater until the organic phosphorus in the membrane concentrate is in solid form, thereby obtaining a concentrated solution a containing solid organic phosphorus and a permeate a;

[0010] 2) performing membrane separation treatment on the membrane concentrate obtained in step 1) to obtain a concentrate b containing solid organic phosphorus and a permeate b containing salt, and evaporating and crystallizing the permeate b containing salt to obtain industrial salt;

[0011] 3) Filtering the concentrated solution b containing solid organic phosphorus to obtain a filtrate concentrate containing solid organic phosphorus and a filtrate clear solution, and drying the filtrate concentrate containing solid organic phosphorus to obtain solid organic phosphorus.

[0012] The present invention treats phosphorus-containing wastewater by first using a membrane concentration process to precipitate diethylaluminum phosphinate organic phosphorus in the wastewater in a solid form, and then using a membrane separation process to separate salt dissolved in the wastewater from the solid diethylaluminum phosphinate, thereby achieving separation and recovery of organic phosphorus and salt. The process is simple and easy to control.

[0013] Preferably, in step 1), the phosphorus-containing wastewater is subjected to filtration pretreatment before being subjected to membrane concentration treatment.

[0014] Preferably, the produced water obtained after the pretreatment enters a subsequent membrane concentration treatment process, and the concentrated water obtained after the pretreatment is returned to the front-end production process.

[0015] Preferably, the filtration pretreatment method is one or more of plate and frame filtration, hollow fiber membrane filtration, tubular membrane filtration, filter bag filtration, and filter element filtration.

[0016] Preferably, the membrane used in the membrane concentration treatment process in step 1) is a nanofiltration membrane and / or a reverse osmosis membrane.

[0017] Preferably, the system used in the membrane concentration process is divided into at least two sections.

[0018] Preferably, the water recovery rate of the membrane concentration system is controlled at 75-90%.

[0019] Preferably, the system used in the membrane concentration treatment process adopts 2 or 3 sections, and each section is composed of 3-6 membrane elements connected in series.

[0020] During the experimental process of the present invention, a single-stage membrane concentration was used in the hair mask concentration process. The concentration multiple of diethylphosphinate aluminum organophosphorus was insufficient, and diethylphosphinate aluminum organophosphorus could not be precipitated in a fixed state from the slurry. Therefore, the membrane concentration system of the present invention adopts at least two stages to precipitate diethylphosphinate aluminum organophosphorus in a fixed state.

[0021] Preferably, when the membrane concentration system has two stages, the operating parameters are: the water recovery rate of the first stage is controlled at 50-60%, and the operating pressure is controlled at 50-70 bar; the water recovery rate of the second stage is controlled at 40-50%, and the operating pressure is controlled at 65-100 bar.

[0022] Preferably, when the membrane concentration system has three sections, the operating parameters are: the water recovery rate of the first section is controlled at 50~60%, and the operating pressure is controlled at 50~70 bar; the water recovery rate of the second section is controlled at 40~50%, and the operating pressure is controlled at 65~100 bar; the water recovery rate of the third section is controlled at 30~50%, and the operating pressure is controlled at 70~100 bar.

[0023] Preferably, in step 1), the phosphorus-containing wastewater is subjected to acid addition to adjust pH and / or temperature reduction treatment before membrane concentration treatment.

[0024] Preferably, the phosphorus-containing wastewater is treated with sulfuric acid to adjust its pH to 2.0-2.5; the temperature of the phosphorus-containing wastewater is reduced to 20-25°C. The present invention can improve the purity of the organophosphorus diethylaluminum phosphinate by acidifying or reducing the pH of the flame retardant wastewater to a certain extent. Furthermore, sulfuric acid is preferably used as the acid for reducing the pH, as it reacts with carbonates in the flame retardant wastewater to form sulfates, thereby increasing the purity of the recovered sodium sulfate.

[0025] Preferably, in step 1), the permeate a enters a primary reverse osmosis concentration treatment to obtain a concentrated liquid c and a permeate c; the permeate c is directly reused or discharged or enters a multi-stage reverse osmosis treatment and then reused; the multi-stage reverse osmosis is not limited to a secondary reverse osmosis, a tertiary reverse osmosis, a quaternary reverse osmosis, and a quintuple reverse osmosis, with a secondary reverse osmosis being preferred; the concentrated water after the multi-stage reverse osmosis treatment is returned to the front end of the primary reverse osmosis, and the multi-stage reverse osmosis produced water is directly reused or discharged.

[0026] Preferably, the concentrated liquid c is returned to the front end of the membrane concentration treatment process in step 1) or the concentrated liquid c is sequentially subjected to medium-pressure reverse osmosis and high-pressure reverse osmosis treatment, or the concentrated liquid c is sequentially subjected to medium-pressure reverse osmosis and butterfly reverse osmosis treatment; the high-pressure reverse osmosis is preferably a spiral high-pressure reverse osmosis; the concentrated water after the high-pressure reverse osmosis or butterfly reverse osmosis treatment is evaporated and crystallized to recover sodium sulfate; the permeate after the above two reverse osmosis treatments is returned to the first-stage reverse osmosis and mixed with the product water of the first-stage reverse osmosis.

[0027] Preferably, the membrane used for membrane separation in step 2) is an ultrafiltration membrane and / or a loose nanofiltration membrane.

[0028] Preferably, the system used for membrane separation is divided into 1, 2 or 3 sections, and each section is composed of 2-4 membrane elements connected in series.

[0029] Preferably, the membrane separation water recovery rate is controlled at 70-95%.

[0030] Preferably, the permeate b containing salt is condensed during the evaporation and crystallization process, and the obtained condensate is reused or directly discharged.

[0031] Preferably, the molecular weight cut-off of the ultrafiltration membrane is 2K~100K.

[0032] Preferably, the divalent salt permeability of the loose nanofiltration membrane is ≥50%.

[0033] Preferably, before filtering the solid organic phosphorus concentrate b in step 3), a diafiltration step is performed to obtain a diafiltration concentrate and a diafiltration permeate. The diafiltration concentrate is then subjected to subsequent filtration, and the diafiltration permeate is evaporated and crystallized to obtain industrial salt. The diafiltration step can significantly improve the purity of the recovered organic phosphorus.

[0034] Preferably, the filtered clear liquid in step 3) is returned to the front-end production process.

[0035] Preferably, the filtered concentrate containing solid organic phosphorus is subjected to condensation treatment during the drying process, and the generated condensate is reused or directly discharged.

[0036] The present invention has the following beneficial effects:

[0037] 1) A membrane concentration process is first used to precipitate the diethylphosphinate aluminum organophosphorus in the waste liquid in a solid form, and then a membrane separation process is used to separate the salt dissolved in the waste water from the solid diethylphosphinate aluminum organophosphorus, thereby achieving separation and recovery of the organophosphorus and salt. The process is simple and easy to control. 2) The diethylphosphinate aluminum organophosphorus and sodium sulfate obtained by resource recovery of the present invention have high purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a process flow chart for resource-based treatment of phosphorus-containing wastewater according to the present invention. Implementation Method

[0039] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following description is given in conjunction with the implementation methods. Example 1

[0040] The water quality indicators of a factory's phosphorus-containing flame retardant production wastewater are: COD content 2500 mg / L, total phosphorus content 800 mg / L, salt content 30000 mg / L (mainly sodium sulfate), pH 3.8, and temperature 55°C.

[0041] like Figure 1 This is the process flow chart for resource-based treatment of phosphorus wastewater in the present invention. The wastewater is first cooled to 25°C through a heat exchanger, and then pre-treated by plate and frame filtration to remove solids. The concentrated water from the plate and frame filtration is returned to the front-end production process, and the produced water enters the subsequent membrane concentration system for further treatment.

[0042] Membrane concentration treatment: The produced water obtained by plate and frame filtration is introduced into the membrane concentration system. The membrane concentration system adopts three sections of membrane concentration units connected in series. The water system recovery rate is 85%. Each section of the membrane concentration unit is composed of four nanofiltration membrane elements connected in series. The operating parameters of each section of the membrane concentration unit are as follows:

[0043] Section 1: Water recovery rate 50%, operating pressure controlled at 55 bar;

[0044] Section 2: Water recovery rate 50%, operating pressure controlled at 70 bar;

[0045] Section 3: Water recovery rate 40%, operating pressure controlled at 75 bar;

[0046] The system maintains the aforementioned operating parameters until the organic phosphorus in the membrane concentrate is precipitated as a fixed substance and suspended in the concentrate. The concentrate enters the membrane separation system for subsequent separation steps. The permeate from the membrane concentration system is filtered through the primary reverse osmosis membrane to produce a primary reverse osmosis permeate and a primary reverse osmosis concentrate. The primary reverse osmosis concentrate is returned to the front end of the membrane concentration process in step 1. The primary reverse osmosis permeate enters the secondary reverse osmosis process, and the secondary reverse osmosis concentrate is returned to the front end of the primary reverse osmosis process. The secondary reverse osmosis permeate is directly reused or discharged. Testing of the secondary reverse osmosis permeate shows a COD content of less than 30 mg / L and a conductivity of less than 50 μs / cm, meeting the water requirements for production processes.

[0047] After treatment by the nanofiltration membrane concentration system, the indicators of the membrane concentration system concentrate water (i.e., the third stage concentrate water) are: COD content 15250 mg / L, total phosphorus content 5107 mg / L, and salt content 166000 mg / L; the indicators of the membrane concentration system product water (mixed product water from stages 1, 2, and 3) are: COD content 250 mg / L, total phosphorus content 40 mg / L, and salt content 6000 mg / L;

[0048] Membrane separation treatment: The concentrated water from the membrane concentration system is introduced into the membrane separation system to obtain membrane separation system product water and membrane separation system concentrated water. The membrane separation system adopts a single-stage type, consisting of three ultrafiltration membrane elements connected in series. The ultrafiltration membrane has a molecular weight cutoff of 2K. The water system recovery rate is controlled at 90%, and the operating pressure is controlled at 3 bar;

[0049] The concentrated water from the membrane separation system was subjected to diafiltration treatment for 3 times. For the first time, water was added in a ratio of 1:1 to the concentrated water from the membrane concentration system to control the system recovery rate to 50%. The second and third diafiltrations were repeated.

[0050] After the above-mentioned diafiltration process, the diafiltration concentrate and diafiltration permeate are obtained. The diafiltration concentrate enters the subsequent filtration process, where the membrane separation system water is mixed with the diafiltration permeate and subjected to evaporation and crystallization to obtain industrial sodium sulfate. After testing, the sodium sulfate yield is 81.5% and the purity is 98.9%.

[0051] Filtration: The concentrated liquid from the membrane separation system is filtered through plate and frame filtration. The filtered supernatant is then returned to the front-end production process. The filtered concentrate is then dried to produce a solid organophosphorus product. The condensate collected during the drying process is then reused or directly discharged. Testing revealed a 62.0% yield and 92.1% purity for the organophosphorus product. Example 2

[0052] The difference between Example 2 and Example 1 is that the primary reverse osmosis concentrated liquid is not returned to the front end of the membrane concentration treatment process in step 1, but is treated by the following method:

[0053] The first-stage reverse osmosis concentrated liquid enters the medium-pressure reverse osmosis treatment to obtain the medium-pressure reverse osmosis permeate and concentrated liquid, and then the medium-pressure reverse osmosis concentrated liquid is introduced into the high-pressure spiral reverse osmosis treatment to obtain the high-pressure spiral reverse osmosis concentrated liquid and permeate. The high-pressure spiral reverse osmosis concentrated liquid is evaporated and crystallized to recover sodium sulfate, and the medium-pressure reverse osmosis and high-pressure spiral reverse osmosis produced water are mixed with the first-stage reverse osmosis permeate and enter the subsequent first-stage reverse osmosis permeate treatment process.

[0054] After calculating the membrane concentration process section, the concentrate was treated with primary reverse osmosis, medium-pressure reverse osmosis and high-pressure spiral reverse osmosis, and then evaporated and crystallized. Finally, after testing, the sodium sulfate yield was 88.6%, the purity was 98.5%, and the organophosphorus product yield was 52.1%, and the purity was 91.1%. Example 3

[0055] The difference between Example 3 and Example 2 is that the high-pressure coil reverse osmosis is replaced by a disc tube reverse osmosis.

[0056] According to the calculated membrane concentration process section, the concentrated liquid is evaporated and crystallized after being treated by first-stage reverse osmosis, medium-pressure reverse osmosis and high-pressure spiral reverse osmosis.

[0057] The yield of sodium sulfate is 88.3% and the purity is 98.7%. The yield of organophosphorus product is 53.2% and the purity is 90.6%. Example 4

[0058] The difference between Example 4 and Example 1 is that the wastewater is cooled to 20° C. using a heat exchanger.

[0059] After testing, the sodium sulfate yield was 81.6%, the purity was 98.6%, the organophosphorus product yield was 65.1%, and the purity was 92.4%. Example 5

[0060] The difference between Example 5 and Example 1 is that no heat exchanger is used to cool the wastewater before the wastewater is treated.

[0061] After testing, the yield of sodium sulfate was 77.3%, the purity was 98.2%, and the yield of organophosphorus product was 50.2%, the purity was 82.0%. Example 6

[0062] The difference between Example 6 and Example 1 is that the wastewater heat exchanger cooling step is replaced by using sulfuric acid to adjust the wastewater pH to 2.

[0063] After testing, the yield of sodium sulfate was 81.5%, the purity was 98.9%, and the yield of organophosphorus product was 62.0%, the purity was 92.1%. Example 7

[0064] The difference between Example 7 and Example 1 is that the wastewater heat exchanger cooling step is replaced by using sulfuric acid to adjust the wastewater pH to 2.5.

[0065] After testing, the yield of sodium sulfate was 81.3%, the purity was 98.7%, and the yield of organophosphorus product was 57.3%, the purity was 91.8%. Example 8

[0066] The difference between Example 8 and Example 1 is that the phosphorus-containing flame retardant production wastewater is not subjected to the plate-and-frame filtration pretreatment step, but is directly introduced into the membrane concentration system for treatment.

[0067] After testing, the yield of sodium sulfate was 80.9%, the purity was 98.3%, and the yield of organophosphorus product was 59.8%, the purity was 91.6%. Example 9

[0068] The difference between Example 9 and Example 1 is that diafiltration is not performed in the membrane separation step.

[0069] Membrane separation treatment: The concentrated water from the membrane concentration system is introduced into the membrane separation system to obtain membrane separation system product water and membrane separation system concentrated water. The membrane separation system adopts a single-stage type, consisting of three ultrafiltration membrane elements connected in series. The ultrafiltration membrane has a molecular weight cutoff of 2K. The water system recovery rate is controlled at 90%, and the operating pressure is controlled at 3 bar;

[0070] The concentrated water from the membrane separation system enters the subsequent filtration process, and the water produced by the membrane separation system is evaporated and crystallized to obtain industrial sodium sulfate.

[0071] After testing, the yield of sodium sulfate was 81.5% and the purity was 98.6%.

[0072] Filtration treatment: The concentrated liquid from the membrane separation system is filtered through plate and frame, and the filtered clear liquid is returned to the front-end production process. The filtered concentrated liquid is then dried to obtain a solid form of organophosphorus product. The condensate collected through condensation during the drying process is reused or directly discharged.

[0073] After testing, the yield of the organophosphorus product was 70.4% and the purity was 55.6%. Example 10

[0074] The difference between Example 10 and Example 1 is that the membrane concentration step adopts a two-stage membrane concentration system, the water system recovery rate is 75%, each membrane concentration unit is composed of four nanofiltration membrane elements connected in series, and the operating parameters set for each membrane concentration unit are as follows:

[0075] Section 1: Water recovery rate 50%, operating pressure controlled at 55 bar;

[0076] Section 2: Water recovery rate 50%, operating pressure controlled at 70 bar.

[0077] After testing, the yield of sodium sulfate was 83.5%, the purity was 98.3%, and the yield of organophosphorus product was 40.2%, the purity was 88.1%.

[0078] Comparative Example 1

[0079] The difference between Comparative Example 1 and Example 1 is that the membrane concentration step adopts a single-stage membrane concentration system. The operating parameters are: water recovery rate 50%, and operating pressure controlled at 55 bar.

[0080] After testing, the sodium sulfate yield was 88.4%, the purity was 95.7%, and the yield of the organophosphorus product was zero.

[0081] Comparative Example 2

[0082] The difference between Comparative Example 2 and Example 1 is that the membrane concentration process is replaced by electrodialysis concentration.

[0083] After testing, the sodium sulfate yield was 81.5%, the purity was 98.6%, and the yield of organophosphorus product was zero.

[0084] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept limited by the claims and the scope of equivalents, the present invention is not limited to the specific details and embodiments described herein.

Claims

1. A method for resource-based treatment of phosphorus-containing wastewater, characterized in that: The following steps are involved: 1) performing membrane concentration treatment on the phosphorus-containing wastewater until the organic phosphorus in the membrane concentrate is in solid form, thereby obtaining a concentrate a containing solid organic phosphorus and a permeate a; The membrane concentration treatment system comprises at least two sections, each section consisting of 3-6 membrane elements connected in series. The operating parameters of the first section are: water recovery rate controlled at 50-60%, and operating pressure controlled at 50-70 bar; the operating parameters of the second section are: water recovery rate controlled at 40-50%, and operating pressure controlled at 65-100 bar. The operation parameters are used until the organic phosphorus in the membrane concentrate is precipitated in solid form and suspended in the concentrate a; 2) performing membrane separation treatment on the membrane concentrate a obtained in step 1) to obtain a concentrate b containing solid organic phosphorus and a permeate b containing salt, and evaporating and crystallizing the permeate b containing salt to obtain industrial salt; 3) filtering the concentrated solution b containing solid organic phosphorus to obtain a filtered concentrated solution containing solid organic phosphorus and a filtered clear solution, and drying the filtered concentrated solution containing solid organic phosphorus to obtain solid organic phosphorus; Wherein, in the step 1), the phosphorus-containing wastewater is cooled or acidified before being subjected to membrane concentration treatment to adjust the pH to 2.0-2.

5.

2. The method for recycling phosphorus-containing wastewater according to claim 1, characterized in that: In the step 1), the phosphorus-containing wastewater is subjected to filtration pretreatment before the membrane concentration treatment; The produced water obtained after the pretreatment enters the subsequent membrane concentration treatment process, and the concentrated water obtained after the pretreatment is returned to the front-end production process; The filtration pretreatment method is one or more of plate and frame filtration, hollow fiber membrane filtration, tubular membrane filtration, filter bag filtration, and filter element filtration.

3. The method for recycling phosphorus-containing wastewater according to claim 1, characterized in that: The membrane used in the membrane concentration treatment process in step 1) is a nanofiltration membrane and / or a reverse osmosis membrane; The water recovery rate of the membrane concentration system is controlled at 75-90%.

4. The method for resource-based treatment of phosphorus-containing wastewater according to claim 3, characterized in that: The system used in the membrane concentration treatment process also includes a third section; The operating parameters of the third stage are: water recovery rate is controlled at 30-50%, and operating pressure is controlled at 70-100 bar.

5. The method for resource-based treatment of phosphorus-containing wastewater according to claim 1, characterized in that: In the step 1), the temperature reduction treatment before the phosphorus-containing wastewater is subjected to membrane concentration treatment is to reduce the temperature of the phosphorus-containing wastewater to 20-25°C.

6. The method for resource-based treatment of phosphorus-containing wastewater according to claim 1, characterized in that: In the step 1), the permeate a enters a first-stage reverse osmosis concentration process to obtain a concentrated solution c and a permeate c; The permeate c is directly reused or is reused after entering multi-stage reverse osmosis treatment; The concentrated liquid c is returned to the front end of the membrane concentration process in step 1) or is sequentially subjected to medium-pressure reverse osmosis and high-pressure reverse osmosis treatments or is sequentially subjected to medium-pressure reverse osmosis and butterfly reverse osmosis treatments.

7. The method for resource-based treatment of phosphorus-containing wastewater according to claim 1, characterized in that: The membrane used for membrane separation in step 2) is an ultrafiltration membrane and / or a loose nanofiltration membrane; The membrane separation system is divided into 1, 2 or 3 sections, each section consists of 2-4 membrane elements connected in series; The membrane separation water recovery rate is controlled at 70-95%; The permeate b containing salt is condensed during the evaporation and crystallization process, and the obtained condensate is reused or directly discharged.

8. The method for resource-based treatment of phosphorus-containing wastewater according to claim 7, characterized in that: The ultrafiltration membrane has a molecular weight cut-off of 2K to 100K; The divalent salt permeability of the loose nanofiltration membrane is ≥50%.

9. The method for resource-based treatment of phosphorus-containing wastewater according to claim 1, characterized in that: In step 3), before filtering the solid organic phosphorus concentrate b, a diafiltration step is performed to obtain a diafiltration concentrate and a diafiltration permeate. The diafiltration concentrate enters a subsequent filtration treatment, and the diafiltration permeate is evaporated and crystallized to obtain industrial salt.

10. The method for resource-based treatment of phosphorus-containing wastewater according to claim 1, characterized in that: The filtered clear liquid in step 3) is returned to the front-end production process; The filtered concentrated liquid containing solid organic phosphorus is subjected to condensation treatment during the drying process, and the generated condensate is reused or directly discharged.

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