Recycling and wastewater zero discharge treatment system for high-salt organic wastewater

Abstract

The utility model relates to a high-salt organic wastewater recycling and wastewater zero discharge treatment system which comprises a pretreatment unit (1), an electro-catalysis unit (2), a nanofiltration feeding pump (3), a nanofiltration unit (4), an electrodialysis unit (5), an evaporation crystallization unit (6), a forward osmosis unit (7), a draw solution storage tank unit (8), a draw solution circulating pump (9) and an evaporation solidification unit (10). According to the utility model, the high-salt organic wastewater is combined with nanofiltration, electrodialysis, forward osmosis and evaporation technologies, so that full-quantitative treatment on one side of pollutants and resource utilization of sodium chloride in the wastewater are realized. Sodium chloride in the wastewater is recycled, meanwhile, the regeneration problem of the forward osmosis draw solution is solved, in addition, the recycled sodium chloride product can be reused in the sewage treatment unit to serve as the draw solution of the forward osmosis unit for further wastewater treatment, and the purpose of treating waste with waste is truly achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment and relates to a high-salt organic wastewater treatment system. Background Art

[0002] High-salinity organic wastewater refers to wastewater with a total salt content of at least 1%, which contains a large amount of salt (Cl - , Ca 2+ 、SO4 2- 、Na + plasma) and difficult-to-degrade organic pollutants, some of which even contain a certain amount of toxic heavy metal ions. It has the characteristics of high salinity, difficulty in biodegradation and high toxicity. It is one of the most difficult wastewaters to treat at present.

[0003] In recent years, domestic and foreign scholars have proposed many "zero emission" treatment processes for high-salt organic wastewater. However, in actual operation, these "zero emission" treatment processes often only achieve zero emission of wastewater liquid, and do not recycle the salt in the wastewater well.

[0004] Forward osmosis technology is a new type of membrane separation technology that uses the osmotic pressure of the solution itself as a driving force. It has the advantages of high interception rate, easy pollution cleaning, simple operation, and high water recovery rate. The water recovery rate can reach 70-90%. Compared with membrane separation processes such as ultrafiltration, nanofiltration, and reverse osmosis, forward osmosis technology basically does not require energy consumption and can achieve sewage treatment through osmotic pressure difference. In the application of forward osmosis technology, the efficient regeneration of the draw liquid is crucial to the entire forward osmosis process, and electrodialysis technology is a membrane separation technology that uses ion migration under the action of an electric field to achieve ion separation and concentration. It can concentrate saline solutions to obtain concentrated water and fresh water with higher concentrations. Therefore, forward osmosis-electrodialysis technology can well solve the problem of draw liquid regeneration in the forward osmosis process, and is also conducive to the efficient and cheap recovery of salts in high-salt wastewater, while realizing the recycling of water resources.

[0005] Chinese patent CN 207227084 U discloses a method and device for treating high-salt and high-COD wastewater based on electrodialysis-forward osmosis technology. During the simultaneous operation of the electrodialysis device and forward osmosis, part of the forward osmosis draw liquid is regenerated by electrodialysis concentration. However, the concentration efficiency and concentrated water volume of the electrodialysis concentration chamber for the draw liquid are limited, which still limits the water purification efficiency of forward osmosis, and there is no resource recovery of salt in the wastewater.

[0006] Chinese patent CN 113896384A discloses a novel high-salt and high-organic wastewater treatment device, which realizes the recovery and utilization of sodium chloride salt by MVR evaporation after salt separation through tubular nanofiltration. However, the purity of the recovered sodium chloride is still low, and the nanofiltration permeate is directly evaporated without further concentration, resulting in a large amount of evaporated water and high cost.

[0007] Therefore, a new, efficient and economical system and method for treating high-salt organic wastewater is needed, which can not only realize the resource utilization of sodium chloride in high-salt wastewater, but also effectively and economically treat the wastewater and realize full quantitative treatment of the pollutant side. Utility Model Content

[0008] In view of the shortcomings of the existing technology, the utility model provides a new high-salt organic wastewater resource recovery and wastewater zero-discharge treatment system. The system combines electrocatalytic oxidation, nanofiltration, forward osmosis, electrodialysis technology and evaporation crystallization technology to gradually treat the organic matter and inorganic salts in the wastewater separately, which not only achieves zero liquid discharge in the wastewater, but also can recycle the sodium chloride salt in the wastewater. In addition, the recovered sodium chloride product can be reused in the sewage treatment system as the draw liquid of the forward osmosis system for further wastewater treatment, truly realizing waste treatment with waste.

[0009] In order to achieve the above-mentioned purpose, the utility model adopts the following technical scheme: The utility model relates to a high-salt organic wastewater resource utilization and wastewater zero-discharge treatment system, comprising a pretreatment unit (1), an electrocatalytic unit (2), a nanofiltration feed pump (3), a nanofiltration unit (4), an electrodialysis unit (5), an evaporation crystallization unit (6), a forward osmosis unit (7), an extraction liquid storage tank unit (8), an extraction liquid circulation pump (9), and an evaporation solidification unit (10): characterized in that the pretreatment unit (1) is connected to the electrocatalytic unit element (2); the electrocatalytic unit (2) is connected to the nanofiltration unit (4) via a nanofiltration feed pump (3); the nanofiltration unit (4) is connected to the electrodialysis unit (5) and the forward osmosis unit (7); the electrodialysis unit (5) is connected to the evaporation crystallization unit (6), the forward osmosis unit (7) and the drawn liquid storage tank unit (8); the evaporation crystallization unit (6) is connected to the drawn liquid storage tank unit (8); the forward osmosis unit (7) is respectively connected to the evaporation solidification unit (10), the electrodialysis unit (5) and the drawn liquid storage tank unit (8);

[0010] High-salinity organic wastewater enters the pretreatment unit (1) from the pretreatment unit inlet, and after pretreatment to remove suspended matter and some organic matter, is discharged from the pretreatment unit outlet into the electrocatalytic unit (2);

[0011] The nanofiltration permeate is discharged from the nanofiltration first outlet (4-1) of the nanofiltration unit (4) and enters the electrodialysis unit (5); the nanofiltration concentrate is discharged from the nanofiltration second outlet (4-2) of the nanofiltration unit (4) and enters the forward osmosis unit (7); the nanofiltration permeate enters the electrodialysis unit (5) from the electrodialysis first inlet (5-1) of the electrodialysis unit (5) to treat Cl- and Na- in the wastewater. +The ions and a small amount of residual organic matter are further separated, and sodium chloride concentrate and electrodialysis fresh water are simultaneously produced; part of the sodium chloride concentrate is discharged through the first electrodialysis outlet (5-2) into the draw liquid storage tank unit (8) as the draw liquid of the forward osmosis unit (7), and the remaining sodium chloride concentrate is discharged through the second electrodialysis outlet (5-3) into the evaporation crystallization unit (6); the electrodialysis fresh water is discharged through the third electrodialysis outlet (5-4) in compliance with the discharge standards;

[0012] The nanofiltration concentrate enters the forward osmosis unit (7) through the first forward osmosis inlet (7-1) to undergo a forward osmosis process. The two sides of the selective permeable membrane in the forward osmosis unit (7) are the nanofiltration concentrate and the saturated sodium chloride solution, respectively, wherein the nanofiltration concentrate is used as the raw material liquid and the saturated sodium chloride solution is used as the draw liquid. Under the action of osmotic pressure, water molecules in the raw material liquid pass through the selective permeable membrane and enter the draw liquid region. When the concentration of the draw liquid decreases from 25% to 15%, the diluted draw liquid enters the concentrated liquid chamber of the electrodialysis unit (5) through the first forward osmosis outlet (7-2) to be concentrated. The nanofiltration concentrate is concentrated through the forward osmosis membrane and then discharged from the second forward osmosis outlet (7-3) to enter the evaporation and solidification unit (10).

[0013] Preferably, in the system for treating high-salt organic wastewater, the pretreatment unit adopts one or more processes such as coagulation, sand filtration, chemical softening, ultrafiltration, etc. to remove suspended matter and part of COD in the raw water.

[0014] Preferably, in the system for treating high-salt organic wastewater, the forward osmosis membrane assembly in the forward osmosis membrane unit is at least one of a plate-type forward osmosis membrane assembly, a roll-type forward osmosis membrane assembly or a tubular forward osmosis membrane assembly.

[0015] Preferably, in the system for treating high-salt organic wastewater, the forward osmosis membrane is oriented so that the active layer of the forward osmosis membrane faces the raw material liquid.

[0016] Compared with the prior art, the beneficial effects of the utility model technology are:

[0017] 1. The utility model combines high-salt organic wastewater with nanofiltration, electrodialysis, forward osmosis and evaporation technology to achieve full quantitative treatment of pollutants and resource utilization of sodium chloride in wastewater. While recovering sodium chloride in wastewater, it also solves the problem of regeneration of forward osmosis draw liquid. In addition, the recovered sodium chloride product can be reused in the sewage treatment unit as the draw liquid of the forward osmosis unit for further wastewater treatment, truly achieving waste treatment with waste.

[0018] 2. Use nanofiltration units to separate monovalent salts and divalent salts in wastewater in advance, so as to facilitate the subsequent recovery of sodium chloride resources while reducing the salinity in the nanofiltration concentrate, which is more conducive to water recovery in the forward osmosis unit.

[0019] 3. Make full use of the characteristics of forward osmosis technology such as low energy consumption, pollution resistance, and high water recovery rate to directly process nanofiltration concentrate and achieve low-cost recovery of water resources.

[0020] 4. The electrodialysis unit further purifies the sodium chloride in the nanofiltration permeate to provide a concentrated solution for the evaporation and crystallization of sodium chloride, which can reduce the amount of evaporated crystallization water while also completing the regeneration of the forward osmosis draw solution, saving costs.

[0021] 5. The sodium chloride evaporation and crystallization unit can not only produce economic products and obtain sodium chloride industrial crude salt, but also provide saturated sodium chloride salt solution for the forward osmosis unit, which relieves the pressure of the electrodialysis unit on the concentration and regeneration of the draw liquid, and can further increase the concentration of the draw liquid and enhance the wastewater cleaning capacity of the forward osmosis unit, while reducing the operating costs of the electrodialysis unit and the forward osmosis unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a preferred high-salt organic wastewater treatment system in the present utility model.

[0023] The figure includes: 1. pretreatment unit; 2. electrocatalytic unit; 3. nanofiltration feed pump; 4. nanofiltration unit; 5. electrodialysis unit; 6. evaporation crystallization unit; 7. forward osmosis unit; 8. extraction liquid storage tank unit; 9. extraction liquid circulation pump; 10. evaporation solidification unit. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. Terms such as "connected" and "connected" used in the description of the present invention should be understood in a broad sense, and may be fixed connection, flange connection, threaded connection, etc. For ordinary technicians in this field, the above terms can be understood according to specific circumstances.

[0025] like Figure 1 As shown, the utility model provides a new high-salt organic wastewater resource utilization and wastewater zero-discharge treatment system, wherein the system includes a pretreatment unit, an electrocatalytic unit, a nanofiltration feed pump, a nanofiltration unit, an electrodialysis unit, an evaporation crystallization unit, a forward osmosis unit, an extraction liquid storage tank, an extraction liquid circulation pump and an evaporation solidification unit. The principle of the utility model is mainly to remove organic pollutants in wastewater by electrocatalysis. The electrocatalytic water obtained is separated by the nanofiltration unit and then further separated and purified by the electrodialysis unit. The sodium chloride salt solution is then coupled to the forward osmosis unit for sewage treatment. Secondly, the sodium chloride salt solution is formed into sodium chloride industrial crude salt and saturated sodium chloride solution through the evaporation crystallization unit, which can be reused on the forward osmosis extraction liquid side, which effectively realizes the recovery of sodium chloride while also solving the problem of wastewater treatment. It includes the following steps:

[0026] (1) High-salt organic wastewater raw water enters pretreatment unit 1 from the pretreatment unit inlet, and after pretreatment, suspended matter and some organic matter are removed, it is discharged from the pretreatment unit outlet into electrocatalytic unit 2. The suspended matter content in the wastewater entering electrocatalytic unit 2 is less than 200 mg / L.

[0027] Specifically, the pretreatment may adopt one or more processes such as coagulation, sand filtration, chemical softening, ultrafiltration, etc., which can synergistically remove suspended solids and some organic matter in the raw water that are prone to scaling.

[0028] (2) The wastewater enters the electrocatalytic unit 2 and undergoes an electrocatalytic oxidation process. After most of the organic matter in the wastewater is catalytically oxidized, the effluent is discharged from the outlet of the electrocatalytic unit and enters the nanofiltration unit.

[0029] Preferably, in the electrocatalytic unit, the anode is a titanium-based precious metal oxide coating electrode, the cathode is stainless steel, and the current is 200-500A / m 2 The COD of the water produced by the electrocatalytic unit is less than 200 mg / L and enters the nanofiltration unit through the outlet of the electrocatalytic unit.

[0030] (3) The effluent from the electrocatalytic unit enters the nanofiltration unit 4 through the nanofiltration feed pump 3, and the wastewater passes through the nanofiltration unit 4 to produce permeate and concentrate. The permeate passing through the nanofiltration membrane has the main ion components of Cl-, Na + The monovalent salt ions can be further purified and separated by the subsequent electrodialysis unit 5 to obtain a concentrated sodium chloride salt solution for evaporation and crystallization recovery.

[0031] Most of the remaining organic matter and salt ions are separated by the nanofiltration membrane to form a nanofiltration concentrate. The nanofiltration permeate is discharged from the first outlet 4-1 of the nanofiltration unit and enters the electrodialysis unit 5; the nanofiltration concentrate is discharged from the second outlet 4-2 of the nanofiltration unit and enters the forward osmosis unit 7.

[0032] The filter membrane in the nanofiltration unit is made of any one of aromatic polyamide and acid cellulose, the filter pore size of the membrane is 1-2nm, and the membrane assembly is a combination of one or more stages of membrane assemblies.

[0033] (4) The nanofiltration permeate enters the electrodialysis unit 5 from the first inlet 5-1 of the electrodialysis unit to treat Cl-, Na + Ions and a small amount of residual organic matter are further separated, and sodium chloride concentrate and electrodialysis fresh water are produced at the same time. Part of the sodium chloride concentrate is discharged through the first electrodialysis outlet 5-2 into the draw liquid storage tank unit 8 as the draw liquid of the forward osmosis unit, and the remaining sodium chloride concentrate is discharged through the second electrodialysis outlet 5-3 into the evaporation crystallization unit 6; the electrodialysis fresh water is discharged through the third electrodialysis outlet 5-4 in compliance with the standards.

[0034] In the electrodialysis unit 5, the electrodialysis current density is 20-50 mA / cm 2 The voltage applied to the electrodialysis membrane unit is 0.2-1V, and the mass fraction of sodium chloride after concentration is 16-22%.

[0035] (5) The nanofiltration concentrate enters the forward osmosis unit 7 through the first forward osmosis inlet 7-1 and undergoes a forward osmosis process. The two sides of the selective permeable membrane in the forward osmosis unit are the nanofiltration concentrate and the saturated sodium chloride solution, respectively, wherein the nanofiltration concentrate is used as the raw material liquid and the saturated sodium chloride solution is used as the draw liquid; the water molecules in the raw material liquid pass through the selective permeable membrane under the action of osmotic pressure and enter the draw liquid area. In this process, the raw material liquid is continuously concentrated to form the forward osmosis concentrate, and the draw liquid is continuously diluted. When the concentration of the draw liquid is reduced from 25% to 15%, the diluted draw liquid enters the concentrated liquid chamber of the electrodialysis unit 5 through the first forward osmosis outlet 7-2 for concentration. After the nanofiltration concentrate is concentrated by the forward osmosis membrane, it is discharged from the second forward osmosis outlet 7-3 and enters the evaporation and curing unit 10.

[0036] The forward osmosis membrane assembly in the forward osmosis membrane unit 8 is at least one of a plate forward osmosis membrane assembly, a roll forward osmosis membrane assembly or a tubular forward osmosis membrane assembly, and the forward osmosis membrane orientation is selected so that the active layer side of the forward osmosis membrane faces the raw material liquid.

[0037] (6) The sodium chloride concentrate obtained in step (4) enters the evaporation crystallization unit 6 through the inlet of the evaporation crystallization unit 6. After evaporation, the sodium chloride concentrate produces sodium chloride industrial salt, sodium chloride saturated solution and condensed water. The sodium chloride saturated solution is discharged into the draw liquid storage tank unit 8 through the first outlet 6-1 of the evaporation crystallization to replenish the draw liquid of the forward osmosis unit; the draw liquid storage tank unit 8 is connected to the draw liquid circulation pump 9, and the draw liquid regenerated in the draw liquid storage tank unit 8 enters the forward osmosis unit from the second inlet 7-4 of the forward osmosis unit through the draw liquid circulation pump 9; the condensed water is discharged through the second outlet 6-2 of the evaporation crystallization unit to meet the standards. The formed sodium chloride industrial salt is transported out from the third outlet 6-3 and can be sold as a chemical product. If necessary, it re-enters the draw liquid storage tank unit 8 to dissolve and increase the osmosis draw liquid.

[0038] The evaporation crystallization unit 6 is one or more of the crystallization processes of MVR, multi-effect isothermal crystallization salt production, and freezing combined with recrystallization.

[0039] (7) The forward osmosis concentrated liquid obtained in step (5) enters the evaporation and curing unit 10 through the first inlet 10-1 of the evaporation and curing unit. The forward osmosis concentrated liquid is cured and crystallized by evaporation to form a solid, evaporation mother liquor and condensed water. The solid is transported out through the first outlet 10-4 of the evaporation and curing unit for treatment; the evaporation mother liquor is discharged through the second outlet 10-3 of the unit and enters the electrocatalytic unit 2 for further treatment; the condensed water enters the nanofiltration unit 4 through the third outlet 10-2 of the unit for further treatment.

[0040] 1. The utility model combines high-salt organic wastewater with nanofiltration, electrodialysis, forward osmosis and evaporation technology to achieve full quantitative treatment of pollutants and resource utilization of sodium chloride in wastewater. While recovering sodium chloride in wastewater, it also solves the problem of regeneration of forward osmosis draw liquid. In addition, the recovered sodium chloride product can be reused in the sewage treatment unit as the draw liquid of the forward osmosis unit for further wastewater treatment, truly achieving waste treatment with waste.

[0041] 2. Use nanofiltration units to separate monovalent salts and divalent salts in wastewater in advance, so as to facilitate the subsequent recovery of sodium chloride resources while reducing the salinity in the nanofiltration concentrate, which is more conducive to water recovery in the forward osmosis unit.

[0042] 3. Make full use of the characteristics of forward osmosis technology such as low energy consumption, pollution resistance, and high water recovery rate to directly process nanofiltration concentrate and achieve low-cost recovery of water resources.

[0043] 4. The electrodialysis unit further purifies the sodium chloride in the nanofiltration permeate to provide a concentrated solution for the evaporation and crystallization of sodium chloride, which can reduce the amount of evaporated crystallization water while also completing the regeneration of the forward osmosis draw solution, saving costs.

[0044] 5. The sodium chloride evaporation and crystallization unit can not only produce economic products and obtain sodium chloride industrial crude salt, but also provide saturated sodium chloride salt solution for the forward osmosis unit, which relieves the pressure of the electrodialysis unit on the concentration and regeneration of the draw liquid, and can further increase the concentration of the draw liquid and enhance the wastewater cleaning capacity of the forward osmosis unit, while reducing the operating costs of the electrodialysis unit and the forward osmosis unit.

Claims

1. A high-salt organic wastewater resource recovery and wastewater zero-discharge treatment system, comprising a pretreatment unit (1), an electrocatalytic unit (2), a nanofiltration feed pump (3), a nanofiltration unit (4), an electrodialysis unit (5), an evaporation crystallization unit (6), a forward osmosis unit (7), an extraction liquid storage tank unit (8), an extraction liquid circulation pump (9), and an evaporation solidification unit (10): characterized in that: The pretreatment unit (1) is connected to the electrocatalytic unit (2); the electrocatalytic unit (2) is connected to the nanofiltration unit (4) via a nanofiltration feed pump (3); the nanofiltration unit (4) is connected to the electrodialysis unit (5) and the forward osmosis unit (7); the electrodialysis unit (5) is connected to the evaporation crystallization unit (6), the forward osmosis unit (7) and the drawn liquid storage tank unit (8); the evaporation crystallization unit (6) is connected to the drawn liquid storage tank unit (8); the forward osmosis unit (7) is respectively connected to the evaporation solidification unit (10), the electrodialysis unit (5) and the drawn liquid storage tank unit (8); The first nanofiltration outlet (4-1) of the nanofiltration unit (4) is connected to the electrodialysis unit (5); the second nanofiltration outlet (4-2) of the nanofiltration unit (4) is connected to the forward osmosis unit (7); the first electrodialysis outlet (5-2) of the electrodialysis unit (5) is connected to the drawn liquid storage tank unit (8), and the second electrodialysis outlet (5-3) of the electrodialysis unit (5) is connected to the evaporation crystallization unit (6); the first forward osmosis outlet (7-2) of the forward osmosis unit (7) is connected to the electrodialysis unit (5), and the second forward osmosis outlet (7-3) is connected to the evaporation solidification unit (10).

2. The system according to claim 1, characterized in that: The pretreatment unit adopts one or more of coagulation, sand filtration, chemical softening and ultrafiltration processes to remove suspended matter and part of COD in the raw water.

3. The system according to claim 1, characterized in that: The forward osmosis membrane assembly in the forward osmosis membrane unit is at least one of a plate-type forward osmosis membrane assembly, a roll-type forward osmosis membrane assembly or a tubular forward osmosis membrane assembly.

4. The system according to claim 1, characterized in that: The orientation of the forward osmosis membrane is such that the active layer of the forward osmosis membrane faces the feed liquid.

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