Process for separating high-chloride organic wastewater by cold method

Abstract

The application provides a process method for cold salt separation of high-chloride organic wastewater, which sequentially comprises a pretreatment section, a concentration section and a salt separation section; the pretreatment section comprises a softening adjustment unit, an electrodialysis I, aerobic biochemical treatment, ozone catalytic oxidation, anaerobic biochemical treatment, secondary biochemical treatment, methane purification and a reuse water pool; the concentration section comprises tubular microfiltration, medium-high pressure reverse osmosis, low pressure reverse osmosis, electrodialysis II and a biological reactor; the salt separation section comprises nanofiltration I, nanofiltration II, a freezing crystallizer and a salt crystallizer; the modified anion exchange membrane and the improved electrodialysis in the pretreatment section can effectively realize the separation of salt and organic matters in the high-chloride organic wastewater, and solve the problem that the organic matters in the high-chloride organic wastewater are difficult to treat; the concentration section realizes the concentration of salt, and also retains most of the organic matters in the desalination liquid, so that high-purity sodium chloride and sodium sulfate decahydrate are obtained in the salt separation section; the cold method is realized for the treatment of the high-chloride organic wastewater, the overall operation condition is mild, the operation is simple, the control is easy, and the cost advantage is obvious.

Description

TECHNICAL FIELD

[0001] The present application relates to a process method for treating wastewater by using a high-chloride salt organic wastewater cold salt separation system, and belongs to the technical field of wastewater treatment. BACKGROUND

[0002] High-chloride salt organic wastewater widely exists in various industries such as chemical industry, pharmaceutical industry, papermaking industry, food processing industry, and mining industry. Due to the high salt content of such wastewater, if a conventional aerobic process is used, the bacteria used need to have strong salt tolerance and impact resistance, and the aerobic process needs a large amount of aeration, which has high energy consumption. From the perspective of energy utilization, the organic matter is finally converted into carbon dioxide, which is contrary to the development concept of "carbon peak and carbon neutral". If the high-chloride salt organic wastewater is treated by an anaerobic process, in addition to the requirement of salt tolerance of anaerobic bacteria, it is also necessary to ensure that the reaction of sulfate-reducing bacteria (SRB) reducing sulfate is as little as possible to ensure the smooth progress of the methanogenesis reaction. However, when the sulfate concentration in the high-chloride salt wastewater is also high, the control of the sulfate reduction and methanogenesis reaction is very difficult, so the method generally requires that the sulfate concentration in the anaerobic reactor is less than 2000 mg / L. Therefore, the method is not suitable for high-chloride salt organic wastewater with a sulfate concentration greater than 2000 mg / L.

[0003] Under the environment of increasingly strict wastewater discharge, the treatment of high-chloride salt organic wastewater also faces a big problem, i.e. proper disposal of salt. At present, the salt separation technology mainly focuses on thermal salt separation, involving high-temperature evaporation crystallization, medium-temperature evaporation crystallization, and cooling system. Not only is the energy consumption large, but also the material is easy to cause crystallization plugging of pipelines and equipment during the transformation between high and low temperatures. At the same time, the purity of the product is greatly affected by the temperature parameters and discharge parameters of each crystallizer, and the overall operation is difficult.

[0004] Membrane separation technology is a new technology that uses separation membranes as the core for separation, concentration, and purification. Commonly used membrane separation technologies include ultrafiltration, nanofiltration, reverse osmosis, etc. The membrane pore size of the above-mentioned membranes is in the nanometer level, which is very easy to be blocked by organic matter and suspended matter. Therefore, the membrane separation technology is mainly used for domestic water purification, and is only limited to end desalination in wastewater treatment. Electrodialysis is a new technology formed on the basis of membrane separation combined with electrochemistry. The semi-permeable membrane used in electrodialysis is an ion exchange membrane, which realizes the separation of anions and cations under the driving of an external direct current electric field. Due to its simple operation and long service life, electrodialysis has been widely used in seawater desalination, brackish water desalination, etc. However, for industrial wastewater, especially high-chloride salt organic wastewater, the water not only contains soluble inorganic salts, but also contains a large amount of organic matter and hardness. During the separation and concentration process, the ion exchange membrane will be polluted and scaled, which seriously affects the service life of the membrane, thereby restricting the further development of the technology. SUMMARY

[0005] In order to solve the above problems, the application provides a process method for cold salt separation of high-chloride organic wastewater, which utilizes membrane technology, especially improved electrodialysis, and combines with freezing crystallization technology, so that most of the organic matters in the wastewater are finally utilized as resources in the form of methane, and the salt is converted into high-purity sodium chloride product and sodium sulfate decahydrate, the wastewater is zero discharged, and the process method has the advantages of mild operation condition, simple operation and low energy consumption.

[0006] In order to achieve the above technical purposes, the application adopts the technical scheme as follows:

[0007] The application provides a process method for cold salt separation of high-chloride organic wastewater, the mass concentration of chloride salt in the high-chloride organic wastewater is greater than the mass concentration of sulfate salt, the total salt mass concentration is greater than 8000 mg / L, the sulfate salt mass concentration is greater than 2000 mg / L, and the COD is greater than 2000 mg / L.

[0008] The process method sequentially comprises a pretreatment section, a concentration section and a salt separation section.

[0009] The pretreatment section comprises a softening adjustment unit, electrodialysis I, aerobic biochemical treatment, ozone catalytic oxidation, anaerobic biochemical treatment, secondary biochemical treatment, methane purification and a reuse water pool; after being subjected to softening adjustment, the wastewater enters the electrodialysis I, the concentrated liquid of the electrodialysis I enters the tubular microfiltration of the concentration section in sequence after being subjected to the aerobic biochemical treatment and the ozone catalytic oxidation treatment, the dilution liquid of the electrodialysis I enters the reuse water pool in sequence after being subjected to the anaerobic biochemical treatment and the secondary biochemical treatment, and the methane generated by the anaerobic biochemical treatment is subjected to the methane purification unit treatment and then is recycled.

[0010] The concentration section comprises tubular microfiltration, medium-high pressure reverse osmosis, low-pressure reverse osmosis, electrodialysis II and a biological reactor; the tubular microfiltration effluent enters the medium-high pressure reverse osmosis, the medium-high pressure reverse osmosis concentrated water enters the electrodialysis II, and the water production enters the low-pressure reverse osmosis; the concentrated liquid of the electrodialysis II enters the nanofiltration I of the salt separation section, and the dilution liquid of the electrodialysis II enters the low-pressure reverse osmosis after being subjected to the biological reactor treatment; the low-pressure reverse osmosis concentrated water enters the ozone catalytic oxidation unit of the pretreatment section, and the low-pressure reverse osmosis water production enters the reuse water pool of the pretreatment section.

[0011] The salt separation section comprises nanofiltration I, nanofiltration II, a freezing crystallizer and a salt crystallizer; the water production of the two-stage nanofiltration is mixed and then enters the salt crystallizer, the nanofiltration I concentrated water enters the nanofiltration II, the nanofiltration II concentrated water enters the freezing crystallizer, and the mirabilite mother liquor generated by the freezing crystallizer and the salt mother liquor generated by the salt crystallizer are backflowed to the electrodialysis II for secondary treatment; the freezing crystallizer obtains the product sodium sulfate decahydrate (mirabilite), and the salt crystallizer obtains the product sodium chloride.

[0012] Further, the electrodialysis I and the electrodialysis II are composed of anion exchange membranes and cation exchange membranes, the anion exchange membranes are modified anion exchange membranes, and the cation exchange membranes are general cation exchange membranes.

[0013] The modified anion exchange membrane is prepared by the following method:

[0014] Step a: linear high polymer is dissolved in an organic solvent, then styrene, divinylbenzene, dioctyl phthalate, benzoyl peroxide and hydrophilic modifier are added respectively, and the reaction is stirred to obtain a high polymer solution, wherein the hydrophilic modifier is selected from one or more of α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin;

[0015] Step b: the high polymer solution prepared in step a is supplemented with an organic solvent, anhydrous zinc chloride and chloromethyl methyl ether are added, and the reaction is stirred, then a precipitant is added, and after filtration, drying and crushing, a powdered chloromethylated polymer is obtained;

[0016] Step c: the polymer prepared in step b is dissolved in N,N-dimethylformamide, and trimethylamine gas is introduced for quaternary amination reaction to obtain a quaternary aminated polymer solution; the quaternary aminated polymer solution is made into a film, the obtained film is immersed in a sodium hydroxide solution for alkalization, then washed with water until neutral, and an anion exchange membrane is obtained;

[0017] Step d: dopamine is dissolved in a Tris-HCl buffer solution, and the pH is adjusted with hydrochloric acid to obtain a dopamine Tris buffer solution;

[0018] Step e: the anion exchange membrane obtained in step c is placed in the dopamine Tris buffer solution, and copper sulfate is added, and the reaction is stirred under the condition of air flow, and the modified anion exchange membrane is obtained after the reaction is completed.

[0019] Further, the linear high polymer in step a is selected from at least one of polyethylene, polypropylene, polyvinyl chloride or polyvinylidene fluoride, and is preferably polyvinyl chloride.

[0020] Further, the organic solvent in step a is selected from at least one of dichloromethane, dichloroethane or chloroform, and is preferably dichloromethane.

[0021] Further, the mass volume concentration of the linear high polymer in step a in the organic solvent is 30-100 mg / mL, and the mass volume concentrations of the styrene, divinylbenzene, dioctyl phthalate, benzoyl peroxide and hydrophilic modifier in the organic solvent are 20-100 mg / mL, 20-100 mg / mL, 5-20 mg / mL, 2-10 mg / mL and 30-50 mg / mL, respectively.

[0022] Further, the stirring reaction temperature in step a is 50-90°C, and the stirring reaction time is 0.5-6 h.

[0023] Further, the supplementing amount of the organic solvent in step b is 0.5-1 times of the amount of the organic solvent used in step a.

[0024] Further, the mass-volume concentration of the anhydrous zinc chloride and the solvent in step b is 15-30 mg / mL, and the volume ratio of the chloromethyl methyl ether to the organic solvent is 0.5:1-2:1.

[0025] Further, the stirring reaction temperature in step b is 30-55℃, and the stirring reaction time is 2-24 h.

[0026] Further, the precipitant in step b is methanol and / or ethanol.

[0027] Further, the mass-volume concentration of the polymer and N,N-dimethylformamide in step c is 15-40 mg / mL.

[0028] Further, the trimethylamine gas in step c is obtained by heating and vaporizing an aqueous trimethylamine solution and drying it with an alkaline drying agent. The alkaline drying agent is one of potassium hydroxide, sodium hydroxide, quicklime and soda lime.

[0029] Further, the quaternary amination reaction time in step c is 10-120 minutes.

[0030] Further, the quaternary aminated polymer solution in step c is cast or flow-casted to form a film, and then dried at a temperature of 50-70℃ for 12-24 h.

[0031] Further, the concentration of the sodium hydroxide solution used for alkalization in step c is 0.1-1 mol / L.

[0032] Further, the concentration of the Tris-HCl buffer in step d is 10-50 mmol / L.

[0033] Further, the mass concentration of dopamine in the solution formed in step d is 0.4-4 g / L, and the hydrochloric acid is adjusted to a pH of 8-9.

[0034] Further, copper sulfate is added in step e to a concentration of 1-20 mmol / L, and the stirring reaction time is 1-12 h. Copper sulfate can induce rapid polymerization of dopamine to form a negatively charged polydopamine electrolyte layer on the surface of the anion exchange membrane, thereby modifying the surface of the membrane.

[0035] Further, the modified anion exchange membrane obtained is stored in a sodium chloride solution; the mass concentration of the sodium chloride solution is 5-20 g / L.

[0036] The skilled person in the art should understand that most of the organic pollutants existing in natural water bodies or sewage, such as surfactants, humic acid, proteins, etc., are negatively charged, and dopamine has strong self-aggregation ability and adsorption capacity, and can increase the negative charge density of the membrane surface, so the surface of the anion exchange membrane modified by polydopamine is negatively charged, has electrostatic repulsion to the negatively charged organic matter in water, and can inhibit the pollution of the organic matter to the anion exchange membrane. The skilled person in the art should also understand that the negative surface charge prevents the pollution of the organic matter through electrostatic action, and also affects the migration rate of inorganic anions, and the more the ionic charge number, the greater the influence, so the influence on sulfate ions is greater than that on chloride ions. The addition of β-cyclodextrin to the anion exchange membrane can impart strong hydrophilicity to the membrane and change the migration rate of anions, among which the migration number of anions with low hydration degree such as bromide ions and nitrate ions relative to chloride ions is reduced, and the migration number of anions with high hydration degree such as sulfate ions relative to chloride ions is increased. On the other hand, the hydrophilicity of the membrane is improved, the van der Waals force between the membrane and the organic matter solute is reduced, the attraction is reduced, and at the same time, a hydration layer can be formed between the hydrophilic membrane and water molecules due to hydrogen bonding, which can further hinder the adsorption of pollutants on the membrane surface. Therefore, after the anion exchange membrane of the present application is modified by β-cyclodextrin and polydopamine, the anti-pollution ability of the membrane is greatly increased, and the selective permeability of sulfate ions is increased.

[0037] Further, the softening of the softening adjustment unit is dehardening, preferably a combined agent of sodium hydroxide and sodium carbonate, sodium hydroxide is added according to 1-4 times the mass concentration of magnesium ions, and sodium carbonate is added according to 1-3 times the mass concentration of calcium ions; the adjustment of the softening adjustment unit is pH adjustment, the acid used is sulfuric acid or hydrochloric acid, the base used is sodium hydroxide, and the pH adjustment range is 6-9.

[0038] Further, the treatment time of the electrodialysis I and the electrodialysis II is 0.5-3h, and the current density is 1-80mA / cm 2 .

[0039] Further, the biological bacteria species of the aerobic biochemical process is a salt-tolerant bacteria, and a full aerobic process is adopted, and one of a BAF, an MBR, a contact oxidation tank, and an MBBR process is selected. The salt-tolerant bacteria is a strain that can tolerate a salt mass concentration of 10-50g / L; and preferably, the salt-tolerant bacteria GXNYJ-DL-1 disclosed in CN114686391A is used, and the preservation number is CGMCC No.20350.

[0040] Further, in the ozone catalytic oxidation, the ozone dosage is 0.1-2 times the required oxidant dosage calculated according to the COD value of the wastewater, the reaction time is 10-120 minutes, and the catalyst is a conventional solid supported metal catalyst.

[0041] Further, the dissolved oxygen of the anaerobic biochemical unit is controlled below 0.1 mg / L, the hydraulic retention time is controlled between 2-96 h, and the water temperature is controlled between 25-38℃.

[0042] Further, the methane purification unit adopts one of the solid desulfurization agent adsorption, biological desulfurization, alkali desulfurization, and amine desulfurization technology to purify the gas generated by the anaerobic biochemical unit, and obtains methane with a purity greater than 96%.

[0043] Further, the secondary biochemical unit adopts common biological strains and one of the A / O, BAF, MBR, SBR, contact oxidation tank, and MBBR processes.

[0044] Further, the tubular microfiltration is mainly used to filter suspended solids, colloids, microorganisms, and the like to prevent the subsequent reverse osmosis membrane from being blocked.

[0045] Further, the medium-high pressure reverse osmosis unit is multi-stage and is composed of multiple medium-high pressure reverse osmosis membrane components, the operating pressure is between 2.0-4.2 Mpa, the salt content of the wastewater can be concentrated to 40-110 g / L, and the overall concentration ratio is 2-10; the low pressure reverse osmosis is single-stage, the operating pressure is 1.0-2.0 Mpa, and the water production rate is 50%-80%.

[0046] Further, the biological reactor adopts the BAF or MBR process, and the biological strains adopt salt-tolerant bacteria.

[0047] Further, the nanofiltration has good selective permeability to chloride ions and good interception effect on sulfate ions, and the sulfate ion interception rate is greater than 90%; the water production rate of the nanofiltration I is 40%-75%, and the water production rate of the nanofiltration II is 30%-65%.

[0048] Further, the operation temperature of the salt crystallizer is controlled between 35-60℃, and concentrated mother liquor is obtained in addition to the sodium chloride product; further, when the salt crystallizer works for a period of time, the concentrated mother liquor returns to the second treatment of the electrodialysis II when the sodium sulfate concentration is as high as 300 g / L, according to the solubility of sodium sulfate between (40 g-49 g) / 100 g water at 35-60℃, when the sodium sulfate concentration is lower than 300 g / L, the sodium sulfate in the salt crystallizer can be kept in a dissolved state, which does not affect the purity of the precipitated sodium chloride product, and ensures that the purity of the sodium chloride product is above 99%.

[0049] Further, the freezing crystallizer operating temperature is controlled at 1-10 DEG C, in addition to obtaining sodium sulfate decahydrate product, there will also be concentrated mother liquor; further, when the freezing crystallizer works for a period of time, the concentrated mother liquor returns to the secondary treatment of electrodialysis II when the sodium chloride concentration is as high as 250 g / L, according to the solubility of sodium sulfate at 1-10 DEG C is between 4.9-9.1 g / 100 g water, and the solubility of sodium chloride is greater than 35 g / 100 g water, therefore at this temperature, sodium sulfate decahydrate can be precipitated by cooling method, and sodium chloride is in dissolved state, when the sodium chloride concentration reaches a certain value, the concentrated liquid is discharged, this method can ensure that the purity of sodium sulfate decahydrate product is always above 99%; further, the sodium sulfate decahydrate can be further dehydrated to obtain sodium sulfate.

[0050] Compared with the prior art, the present application has the following advantages:

[0051] (1) In the pretreatment section, the modified anion exchange membrane and the improved electrodialysis of the present application can effectively separate salt and organic matter in high-chloride organic wastewater, solving the problem of difficult treatment of organic matter in high-chloride organic wastewater; the modified anion exchange membrane has the characteristics of strong anti-pollution ability and high ion exchange rate, and has high application value; most of the separated organic matter is converted into methane under anaerobic reaction conditions, realizing resource recycling;

[0052] (2) In the concentration section, the modified anion exchange membrane and the improved electrodialysis of the present application not only realize the concentration of salt, but also retain most of the organic matter in the dilution liquid, thereby reducing the organic matter content in the salt separation section and greatly increasing the product purity.

[0053] (3) In the salt separation section, since the nanofiltration membrane has a very high rejection rate for sulfate, the proportion of sodium chloride in the salt crystallizer is very high, and the purity of the sodium chloride obtained by crystallization is also very high; the separation of sodium chloride by two-stage nanofiltration also greatly increases the proportion of sodium sulfate in the total salt in the freezing crystallizer, and in addition, the freezing crystallization method for preparing sodium sulfate is to convert sodium sulfate from liquid phase to solid phase by cooling without obvious concentration of wastewater, at this time, sodium chloride is in liquid phase and dissolved state, therefore, sodium sulfate decahydrate with higher purity can be obtained.

[0054] (4) The freezing crystallization method for preparing sodium sulfate has a heat exchange temperature difference of only 25-30 DEG C, compared with the heat exchange temperature difference of 70-100 DEG C in the traditional hot method, the energy consumption advantage is significant, and in addition, the membrane technologies such as improved electrodialysis, reverse osmosis, nanofiltration, etc. make the separation of salt and organic matter, the separation of sodium sulfate and sodium chloride, and the crystallization of sodium sulfate and sodium chloride all under normal temperature or low temperature conditions, truly realizing the full "cold method" treatment of high-chloride organic wastewater, the overall operation condition is mild, the operation is simple and easy to control, and the cost advantage is obvious.

[0055] Other features and advantages of the present application will be described in detail in the following detailed description section. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 Process flow chart of treating high-chloride salt organic wastewater in Example 1. DETAILED DESCRIPTION

[0057] The present application will be further described in detail below in conjunction with specific examples. The examples are implemented on the premise of the technical solution of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0058] Example 1

[0059] The process flow chart of treating high-chloride salt organic wastewater is shown in Figure 1 As shown in the process flow chart, the high-chloride salt organic wastewater first enters a softening adjusting tank, and after being subjected to hardening removal and pH adjustment, enters electrodialysis I; the dilute liquid of the electrodialysis I enters anaerobic biochemistry, and the effluent of the anaerobic biochemistry is subjected to secondary biochemical treatment and then enters a reuse water tank; the methane produced by the anaerobic biochemistry is treated by a methane purification unit and then recycled; the concentrated liquid of the electrodialysis I enters aerobic biochemistry, and the effluent of the aerobic biochemistry enters ozone catalytic oxidation; the effluent of the ozone catalytic oxidation is filtered by a tubular microfiltration, and then enters medium-high pressure reverse osmosis; the water produced by the medium-high pressure reverse osmosis is treated by low pressure reverse osmosis, and then the water produced is discharged to the reuse water tank, and the concentrated water is sent back to the ozone catalytic oxidation for secondary treatment; the concentrated water of the medium-high pressure reverse osmosis flows to electrodialysis II, the dilute liquid of the electrodialysis II flows to a biological reactor, and the effluent of the biological reactor enters low pressure reverse osmosis; the concentrated liquid of the electrodialysis II enters two-stage nanofiltration, and the water produced by the two-stage nanofiltration is mixed and then enters a salt crystallizer; the concentrated water of the nanofiltration I enters the nanofiltration II, the concentrated water of the nanofiltration II enters a refrigeration crystallizer, the refrigeration crystallizer obtains product sodium sulfate decahydrate (mirabilite), the salt crystallizer obtains product sodium chloride, and the mirabilite mother liquor produced by the refrigeration crystallizer and the salt mother liquor produced by the salt crystallizer are refluxed together to the electrodialysis II for secondary treatment.

[0060] The high-chloride salt organic wastewater is treated by the process method of the present application.

[0061] A high-chloride salt organic wastewater has the following water quality: COD 2200 mg / L, sulfate 2500 mg / L, chloride salt concentration 5000 mg / L, calcium ion concentration 150 mg / L, magnesium ion concentration 50 mg / L, total salt content 12100 mg / L, pH 5, wastewater flow rate 20 t / h, mass ratio of chloride salt to sulfate 2:1, and neutral organic matter (uncharged) as the main organic matter in the wastewater.

[0062] The electrodialysis I and the electrodialysis II provided in the embodiment are both modified electrodialysis, wherein the anion exchange membrane is a modified anion exchange membrane, which has strong anti-pollution ability and high ion permeability, and the cation exchange membrane is a general cation exchange membrane (CJ-MC-3, China Hefei Kaijie Polymer Co., Ltd.).

[0063] The modified anion exchange membrane is prepared by the following method:

[0064] In step a, linear high polymer polyvinyl chloride is dissolved in 1 volume of organic solvent dichloromethane, the mass-volume concentration of the linear high polymer in the organic solvent is 58 mg / mL, and styrene, divinylbenzene, dioctyl phthalate, benzoyl peroxide and hydrophilic modifier β-cyclodextrin are added in mass-volume concentrations of 48 mg / mL, 42 mg / mL, 9 mg / mL, 7 mg / mL and 46 mg / mL respectively, and the mixture is stirred and reacted at a temperature of 75 °C for 3 h to obtain a high polymer solution;

[0065] In step b, 0.65 volumes of organic solvent dichloromethane are added to the high polymer solution prepared in step a, anhydrous zinc chloride and chloromethyl methyl ether are added, the mass-volume concentration of anhydrous zinc chloride in dichloromethane is 24 mg / mL, and the volume ratio of chloromethyl methyl ether to solvent is 1.3:1, and after stirring and reacting at a temperature of 45 °C for 12 h, a precipitant methanol is added, and the mixture is filtered, dried and crushed to obtain a powdered chloromethylated polymer;

[0066] In step c, the polymer prepared in step b is dissolved in N,N-dimethylformamide, and the mass-volume concentration of the polymer in N,N-dimethylformamide is 28 mg / mL; a trimethylamine aqueous solution is heated and vaporized, and the trimethylamine gas is dried by a basic drying agent and then introduced into the above-mentioned N,N-dimethylformamide solution of the polymer, and the reaction time is 70 minutes to obtain a quaternary aminated polymer solution; the quaternary aminated polymer solution is cast to form a film, and the film is dried at 60 °C for 18 h to form a membrane; the obtained membrane is immersed in a 0.55 mol / L sodium hydroxide solution for alkalization, and then washed with deionized water until neutral to obtain an anion exchange membrane;

[0067] In step d, dopamine is dissolved in a 20 mmol / L Tris-HCl buffer solution, and the pH is adjusted to 8.5 with hydrochloric acid to obtain a dopamine Tris buffer solution, and the mass concentration of dopamine in the buffer solution is 1 g / L;

[0068] In step e, the polyvinyl alcohol anion exchange membrane to be modified is placed in the dopamine Tris buffer solution, and 5 mmol / L copper sulfate is added, and the mixture is stirred and reacted for 6 h while maintaining air flow, wherein the copper sulfate can induce rapid polymerization of dopamine to form a negatively charged polydopamine electrolyte layer on the surface of the anion exchange membrane, and the modified anion exchange membrane is obtained after the reaction is completed.

[0069] Step f: The modified anion exchange membrane prepared in step e was taken out and placed in a 10 g / L sodium chloride solution for use.

[0070] The specific operation parameters for treating high-chloride organic wastewater are as follows:

[0071] The wastewater first enters the softening adjustment tank, and the hardness removal agent is added according to the mass concentration of sodium hydroxide 110 mg / L and the mass concentration of sodium carbonate 300 mg / L, and the pH is adjusted to 7 by adding sodium hydroxide. After clarification, the supernatant calcium ion concentration is reduced to below 10 mg / L, and the magnesium ion concentration is reduced to below 5 mg / L. The effluent enters the electrodialysis I; the treatment time of electrodialysis I is 1 h, and the current density is 25 mA / cm 2 After treatment, the dilution liquid in electrodialysis I has a COD concentration of 2816 mg / L and a salt content of 2630 mg / L, a flow rate of 15 t / h, a concentrated liquid COD concentration of 352 mg / L, a salt content of 40510 mg / L, a flow rate of 5 t / h, a sulfate ion selective permeability of 79.1%, a chloride ion selective permeability of 85.5%, and an organic matter interception rate of 96%; the dilution liquid of electrodialysis I enters the anaerobic biochemical unit, with a residence time of 16 h and a water temperature of 32℃, and the dissolved oxygen is less than 0.1 mg / L. The produced methane is purified by alkali solution, and the purity reaches 98.2%. The COD concentration of the effluent of the anaerobic biochemical unit is 255 mg / L, and the salt content is 2560 mg / L, which enters the secondary biochemical unit; the secondary biochemical unit adopts A / O process, and the conventional activated sludge is added, with a residence time of 10 h. The final effluent COD concentration is 46 mg / L, and the salt content is 2555 mg / L, which meets the reuse standard and enters the reuse tank; the electrodialysis concentrated liquid enters the aerobic biochemical unit, which adopts MBR process, with a salt concentration close to 40 g / L, and the salt-tolerant bacteria are added. The high-efficiency salt-tolerant bacteria GXNYJ-DL-1 in the patent CN114686391A are selected, with a preservation number of CGMCC No.20350, and the residence time is 8 h. The effluent COD is as low as 120 mg / L, and then enters the ozone catalytic oxidation unit. The ozone addition concentration is 80 mg / L, and the reaction time is 30 min. The effluent COD is 56 mg / L, which is filtered by tubular microfiltration and then enters the medium-high pressure reverse osmosis unit.

[0072] The operating pressure of the medium-high pressure reverse osmosis is between 3-4.2 Mpa, the salt content of the concentrated water is close to 100 g / L after concentration, and the concentration multiple is 2.5; the salt content of the water produced by the medium-high pressure reverse osmosis is 3-10 g / L, which enters the low pressure reverse osmosis, the low pressure reverse osmosis is a first stage, the operating pressure is 1.5 Mpa, the water production rate is 71%, the salt content of the concentrated water is greater than 10 g / L, and the COD is higher than 60 mg / L, which is returned to the ozone catalytic oxidation unit for secondary treatment, the COD of the water produced by the low pressure reverse osmosis is lower than 60 mg / L, the salt content is lower than 2500 mg / L, and the reuse requirement is met; the concentrated water of the medium-high pressure reverse osmosis enters the electro-dialysis II, the salt content of the concentrated water of the medium-high pressure reverse osmosis is about 100 g / L, the COD is 168 mg / L, the treatment time of the electro-dialysis II is 1.2 h, and the current density is 25 mA / cm 2 After treatment, the salt content of the concentrated liquid of the electro-dialysis II is about 200 g / L, the COD is 33 mg / L, the water amount of the concentrated liquid accounts for 38% of the total amount of the inlet water, the salt content of the diluted liquid is about 39 g / L, the COD is 251 mg / L, and the water amount of the diluted liquid accounts for 62% of the total amount of the inlet water; the diluted liquid of the electro-dialysis II enters the biological reactor, the BAF process is adopted, the salt-tolerant bacteria are added, the high-efficiency salt-tolerant bacteria GXNYJ-DL-1 in the patent CN114686391A is selected, the residence time is 6 h, the COD of the outlet water is as low as 75 mg / L, the COD is less than 40 mg / L after the low pressure reverse osmosis treatment, and the salt content is lower than 2500 mg / L, which meets the reuse requirement.

[0073] The concentrated liquid of the electro-dialysis II enters two-stage nanofiltration, the water production rate of the first-stage nanofiltration is 50%, the water production rate of the second-stage nanofiltration is 40%, the salt content of the mixed water produced by the two-stage nanofiltration is about 172 g / L, the proportion of chloride salt is more than 90%, the salt content of the concentrated water of the nanofiltration II is about 265 g / L, and the proportion of sulfate is more than 80%; the water produced by the two-stage nanofiltration enters the salt crystallizer, the temperature of the salt crystallizer is controlled at 50 DEG C, sodium chloride with a purity of 99.2% is obtained through crystallization, the mother liquor is continuously concentrated to a sodium sulfate mass concentration of 300 g / L, the concentrated mother liquor is returned to the electro-dialysis II for secondary treatment without affecting the product purity; the concentrated water of the nanofiltration II enters the refrigeration crystallizer, the temperature is controlled at 4 DEG C, sodium sulfate decahydrate is precipitated due to the reduction of solubility, the product purity is 99.6%, and the mother liquor is continuously concentrated to a sodium chloride mass concentration of 250 g / L, the concentrated mother liquor is returned to the electro-dialysis II for secondary treatment without affecting the product purity.

[0074] It can be seen from the embodiment that the application can effectively treat high-chloride organic wastewater, most of the wastewater is recycled after simple biochemical treatment through the improved pretreatment of electro-dialysis, and high-purity methane is obtained; the high-salt component is moderately treated through aerobic biochemical treatment and ozone catalytic oxidation, concentrated and separated through membrane technologies such as reverse osmosis, improved electro-dialysis and nanofiltration, and finally realizes zero discharge, and high-purity sodium chloride and sodium sulfate decahydrate are prepared. The overall operation condition of the process route is mild, the operation is simple, and the energy consumption is low.

[0075] Example 2

[0076] Utilizing Figure 1 The process shown is used to treat a high-chloride organic wastewater.

[0077] The wastewater quality is as follows: COD 4500 mg / L, sulfate 3000 mg / L, chloride concentration 7500 mg / L, which is a high-chloride organic wastewater. In addition, the calcium ion concentration is 100 mg / L, the magnesium ion concentration is 100 mg / L, the total salt content is 17000 mg / L, the pH is 10, the wastewater flow is 20 t / h, the mass ratio of chloride to sulfate is 5:2, and the organic matter in the wastewater is mainly neutral organic matter (uncharged).

[0078] The process route and implementation steps for treating the high-chloride organic wastewater in this example are the same as in Example 1. The electrodialysis I and electrodialysis II in the process route are both modified electrodialysis, as in Example 1, in which the anion exchange membrane is a modified anion exchange membrane, and the cation exchange membrane is a general-purpose cation exchange membrane (Hefei Kaitie Polymer Co., Ltd., China, model CJ-MC-3). In the preparation of the modified anion exchange membrane, in addition to the linear polymer in step a being polyethylene, the mass-volume concentration of β-cyclodextrin is 55 mg / ml, the volume ratio of chloromethyl methyl ether to solvent in step b is 1.5:1, and the stirring reaction time is 12 h, the other steps are the same as in Example 1.

[0079] The specific operation parameters for treating the high-chloride organic wastewater are as follows:

[0080] The wastewater first enters the softening adjustment tank, and the hardness removal reagent is added according to the mass concentration of sodium hydroxide 200 mg / L and the mass concentration of sodium carbonate 200 mg / L, and sulfuric acid is added to adjust the pH to 7. After clarification, the supernatant calcium ion concentration is reduced to below 10 mg / L, and the magnesium ion concentration is reduced to below 5 mg / L. The effluent enters the electrodialysis I; the treatment time of the electrodialysis I is 1.15 h, the current density is 30 mA / cm 2, the COD concentration of the diluted liquid in the electro-dialysis I after treatment is 6542 mg / L, the salt content is 3020 mg / L, the flow rate is 13 t / h, the COD concentration of the concentrated liquid is 707 mg / L, the salt content is 42962 mg / L, the flow rate is 7 t / h, the selectivity permeation rate of sulfate ions is 85.2%, the selectivity permeation rate of chloride ions is 90.5%, and the interception rate of organic matter is 94.5%; the diluted liquid in the electro-dialysis I enters the anaerobic biochemical unit, the residence time is 30 h, the water temperature is 32℃, the dissolved oxygen is less than 0.1 mg / L, the purity of the generated methane after purification by alkali liquid reaches 98.8%, the COD concentration of the effluent of the anaerobic biochemical unit is 458 mg / L, the salt content is 2950 mg / L, and the effluent enters the secondary biochemical unit; the secondary biochemical unit adopts the SBR process, the conventional activated sludge is added, the residence time is 16 h, the COD concentration of the final effluent is 55 mg / L, the salt content is 2935 mg / L, which meets the recycling standard, and the effluent enters the recycling pool; the concentrated liquid of the electro-dialysis enters the aerobic biochemical unit, the aerobic biochemical unit adopts the BAF process, the salt concentration is close to 43 g / L, the salt-tolerant bacteria are added, the high-efficiency salt-tolerant bacteria GXNYJ-DL-1 in the patent CN114686391A is selected, the residence time is 16 h, the COD concentration of the effluent is as low as 150 mg / L, and then the effluent enters the ozone catalytic oxidation unit, the ozone adding concentration is 100 mg / L, the reaction time is 30 min, the COD concentration of the effluent is 61 mg / L, and the effluent is filtered by the tubular microfiltration and then enters the medium-high pressure reverse osmosis unit.

[0081] The operating pressure of the medium-high pressure reverse osmosis is between 3 and 4.2 Mpa, the salt content of the concentrated water after concentration is close to 100 g / L, and the concentration multiple is 2.3; the salt content of the water produced by the medium-high pressure reverse osmosis is 3-10 g / L, the water enters the low-pressure reverse osmosis, the low-pressure reverse osmosis is the first level, the operating pressure is 1.5 Mpa, the water production rate is 72%, the salt content of the concentrated water is greater than 10 g / L, and the COD is higher than 60 mg / L, which is returned to the ozone catalytic oxidation unit for secondary treatment, the COD of the water produced by the low-pressure reverse osmosis is lower than 60 mg / L, the salt content is lower than 2500 mg / L, which meets the recycling requirements; the concentrated water of the medium-high pressure reverse osmosis enters the electro-dialysis II, the salt content of the concentrated water of the medium-high pressure reverse osmosis is about 100 g / L, the COD is 190 mg / L, the treatment time of the electro-dialysis II is 1.2 h, the current density is 30 mA / cm 2, the salt content of the concentrated solution of the electro-dialysis II is about 205 g / L, the COD is 35 mg / L, the water volume of the concentrated solution accounts for 40% of the total water volume of the influent, the salt content of the dilute solution is about 30 g / L, the COD is 293 mg / L, and the water volume of the dilute solution accounts for 60% of the total water volume of the influent; the dilute solution of the electro-dialysis II enters a biological reactor, an MBR process is adopted, salt-tolerant bacteria are added, the high-efficiency salt-tolerant bacteria GXNYJ-DL-1 in the patent CN114686391A is selected, the preservation number is CGMCC No. 20350, the residence time is 8 h, the effluent COD is as low as 80 mg / L, the COD is less than 40 mg / L after the effluent is treated by low-pressure reverse osmosis, and the salt content is less than 2300 mg / L, which meets the recycling requirements.

[0082] The concentrated solution of the electro-dialysis II enters two-stage nanofiltration, the water yield of the first-stage nanofiltration is 60%, the water yield of the second-stage nanofiltration is 50%, the salt content of the mixed water produced by the two-stage nanofiltration is about 190 g / L, the proportion of chloride salt is more than 90%, the salt content of the concentrated water of the nanofiltration II is about 240 g / L, and the proportion of sulfate salt is more than 80%; the water produced by the two-stage nanofiltration enters a salt crystallizer, the temperature of the salt crystallizer is controlled at 52 ℃, sodium chloride with a purity of 99.3% is obtained by crystallization, when the mother liquor is concentrated to a sodium sulfate mass concentration of 300 g / L, in order not to affect the product purity, the concentrated mother liquor is returned to the electro-dialysis II for secondary treatment; the concentrated water of the nanofiltration II enters a refrigeration crystallizer, the temperature is controlled at 3 ℃, sodium sulfate decahydrate is precipitated due to the reduction of solubility, the product purity is 99.7%, and when the sodium chloride mass concentration of the mother liquor is concentrated to 250 g / L, in order not to affect the product purity, the concentrated mother liquor is returned to the electro-dialysis II for secondary treatment.

[0083] It can be seen from the embodiment that the application can effectively treat high-chloride salt organic wastewater with different concentrations, most of the organic matters are realized as resource utilization in the form of methane, the wastewater is finally realized as zero emission, and high-purity sodium chloride and sodium sulfate decahydrate are prepared. The overall process route has mild operation conditions, simple operation, and low energy consumption.

[0084] Comparative Example 1

[0085] The high-chloride salt organic wastewater treated in Comparative Example 1 has the same water quality as that in Example 2, the process route and implementation steps are also the same as those in Example 2, and the difference is that the anion exchange membrane and the cation exchange membrane of the electro-dialysis I are both general membranes and are not modified, the anion exchange membrane is a product of Asahi Glass Company, Japan (SELEMION AMV), and the cation exchange membrane is a product of Hefei Kaitai Polymer Co., Ltd., China (model CJ-MC-3).

[0086] Specifically, the wastewater first enters a softening adjustment tank, the adding amount of sodium hydroxide and sodium carbonate is the same as that in Example 2, and the effluent enters the ordinary electro-dialysis I; the treatment time of the ordinary electro-dialysis I is 1.15 h, the current density is 30 mA / cm 2, the COD concentration of the dilute liquid after treatment in the first electrodialysis was 5607 mg / L, the salt content was 6407 mg / L, the flow rate was 13 t / h, the COD concentration of the concentrated liquid was 2444 mg / L, the salt content was 36671 mg / L, the flow rate was 7 t / h, the selective permeation rate of sulfate ions was 71.5%, and the selective permeation rate of chloride ions was 78.4%, which was significantly lower than that in Example 2, and the membrane flux decreased significantly, which might be related to membrane clogging. In addition, the rejection rate of organic matter decreased to 81%, indicating that a large amount of negatively charged organic matter passed through the anion membrane, increasing the possibility of membrane clogging. The dilute liquid after treatment in the first electrodialysis entered the anaerobic biochemical unit, with a residence time of 30 h, a water temperature of 32°C, and a dissolved oxygen of less than 0.1 mg / L. The COD concentration of the effluent from the anaerobic biochemical unit was 3658 mg / L, and the salt content was 5950 mg / L, which entered the secondary biochemical unit. The secondary biochemical unit used the SBR process, and the conventional activated sludge was added, with a residence time of 16 h. The final effluent COD concentration was 2813 mg / L, and the salt content was 5735 mg / L, which did not meet the reuse standard. Analysis showed that the high salt concentration led to poor biochemical effect. The concentrated liquid from the first electrodialysis entered the aerobic biochemical unit, which used the BAF process. The salt concentration was close to 37 g / L, and the salt-tolerant bacteria were added. The high-efficiency salt-tolerant bacteria GXNYJ-DL-1 in the patent CN114686391A were selected, with a preservation number of CGMCC No. 20350. The residence time was 16 h, the effluent COD was as low as 1680 mg / L, and then it entered the ozone catalytic oxidation unit. The ozone addition concentration was 100 mg / L, the reaction time was 30 min, the effluent COD was 1535 mg / L, and after pipe microfiltration, it entered the medium-high pressure reverse osmosis unit. Due to the high COD concentration, the reverse osmosis unit was seriously clogged.

[0087] From the present comparative example, it can be seen that the first electrodialysis uses unmodified cation and anion exchange membranes, which cannot effectively separate organic matter and salt, resulting in high salt content in the biochemical unit, and the wastewater cannot be treated to meet the reuse standard. In addition, the organic matter concentration in the concentration unit is too high, and the salt concentration section and the salt separation section cannot operate normally.

[0088] Comparative Example 2

[0089] Comparative Example 2 treated high-chloride salt organic wastewater in the same way as Example 2. The process route and implementation steps were the same as those in Example 2. The first electrodialysis was the same as Example 2, which was also modified electrodialysis. The difference was that the cation and anion exchange membranes in the second electrodialysis were general type membranes, which were not modified. The anion exchange membrane used the product of Japan Asahi Glass Company (SELEMION AMV), and the cation exchange membrane used the product of Hefei Kaitai Polymer Co., Ltd. (model CJ-MC-3).

[0090] Specifically: consistent with Example 2, after the wastewater is treated by the pretreatment section and the concentration section, the high-pressure reverse osmosis unit concentrated water enters the electrodialysis II, the high-pressure reverse osmosis concentrated water salt content is about 100 g / L, the COD is 190 mg / L, the electrodialysis II treatment time is 1.2 h, and the current density is 30 mA / cm 2 After treatment, the electrodialysis II concentrated liquid salt content is about 167 g / L, the COD is 130 mg / L, the concentrated liquid water accounts for 40% of the total amount of the influent, the desalination liquid salt content is about 56 g / L, the COD is 230 mg / L, and the desalination liquid water accounts for 60% of the total amount of the influent; the electrodialysis II desalination liquid enters the biological reactor, the MBR process is adopted, the salt-tolerant bacteria are added, the high-efficiency salt-tolerant bacteria GXNYJ-DL-1 in the patent CN114686391A is selected, the preservation number is CGMCC No. 20350, the residence time is 8 h, the effluent COD is as low as 58 mg / L, and the low-pressure reverse osmosis is entered; the low-pressure reverse osmosis water production rate is 72%, the effluent COD is less than 40 mg / L after treatment, and the salt content is 4070 mg / L; generally, the industrial water such as circulating water requires that the salt is less than 3000 mg / L, so the reverse osmosis water cannot meet the recycling requirements; the electrodialysis II concentrated liquid salt content is relatively low, the COD is relatively high, and finally the subsequent crystallization efficiency is reduced, the product sodium sulfate decahydrate purity is reduced to 98.8%, and the sodium chloride purity is reduced to 98.6%.

[0091] It can be known from the present comparative example that the electrodialysis II adopts unmodified anion and cation exchange membranes, the separation ability of the organic matter and the salt is poor, the anion exchange membrane is easily polluted by the organic matter, the desalination liquid is difficult to treat to reach the standard recycling, and the purity of the sodium sulfate decahydrate and the sodium chloride prepared from the concentrated liquid is reduced.

Claims

1. A process for separating salts from high-chloride organic wastewater by cooling method, wherein the chloride concentration in the high-chloride organic wastewater is greater than the sulfate concentration, the total salt concentration is greater than 8000 mg / L, the sulfate concentration is greater than 2000 mg / L, and the COD is greater than 2000 mg / L; The process method includes, in sequence, a pretreatment section, a concentration section, and a salt separation section; The pretreatment section includes a softening and conditioning unit, electrodialysis I, aerobic biochemical treatment, ozone catalytic oxidation, anaerobic biochemical treatment, secondary biochemical treatment, methane purification, and a reclaimed water tank. After softening and conditioning, the wastewater enters electrodialysis I. The concentrate from electrodialysis I is then treated sequentially by aerobic biochemical treatment and ozone catalytic oxidation before entering the tubular microfiltration section of the concentration unit. The desalinated liquid from electrodialysis I is then treated sequentially by anaerobic biochemical treatment and secondary biochemical treatment before entering the reclaimed water tank. The methane produced by anaerobic biochemical treatment is purified and then recycled. The concentration section includes tubular microfiltration, medium- and high-pressure reverse osmosis, low-pressure reverse osmosis, electrodialysis II, and a bioreactor. The effluent from the tubular microfiltration enters the medium- and high-pressure reverse osmosis, the concentrate from the medium- and high-pressure reverse osmosis enters the electrodialysis II, and the permeate enters the low-pressure reverse osmosis. The concentrate from the electrodialysis II enters the nanofiltration I in the salt separation section, and the desalinated solution from the electrodialysis II is treated by the bioreactor before entering the low-pressure reverse osmosis. The concentrate from the low-pressure reverse osmosis enters the ozone catalytic oxidation in the pretreatment section, and the permeate from the low-pressure reverse osmosis enters the reclaimed water tank in the pretreatment section. The salt separation section includes nanofiltration I, nanofiltration II, a cryogenic crystallizer, and a salt crystallizer. The permeate from the two nanofiltration stages is mixed and then enters the salt crystallizer. The concentrate from nanofiltration I enters nanofiltration II, and the concentrate from nanofiltration II enters the cryogenic crystallizer. The sodium sulfate mother liquor produced by the cryogenic crystallizer and the salt mother liquor produced by the salt crystallizer are refluxed together to electrodialysis II for secondary treatment. The cryogenic crystallizer produces sodium sulfate decahydrate, and the salt crystallizer produces sodium chloride. Electrodialysis I and electrodialysis II are composed of anion and cation exchange membranes, wherein the anion exchange membrane is a modified anion exchange membrane and the cation exchange membrane is a general-purpose cation exchange membrane; The modified anion exchange membrane is prepared by the following method: Step a: Dissolve the linear polymer in an organic solvent, then add styrene, divinylbenzene, dioctyl phthalate, benzoyl peroxide, and a hydrophilic modifier, respectively, and stir to obtain a polymer solution. The hydrophilic modifier is selected from one or more of α-cyclodextrin, β-cyclodextrin or γ-cyclodextrin; Step b: Add organic solvent to the polymer solution obtained in step a, add anhydrous zinc chloride and chloromethyl methyl ether, stir to react, then add precipitant, and then filter, dry and pulverize to obtain powdered chloromethylated polymer; Step c: Dissolve the chloromethylated polymer obtained in step b in N,N-dimethylformamide, introduce trimethylamine gas, and carry out a quaternization reaction to obtain a quaternized polymer solution; prepare a membrane from the quaternized polymer solution, immerse the membrane in sodium hydroxide solution for alkalization, and then wash it with water until neutral to obtain an anion exchange membrane. Step d: Dissolve dopamine in Tris-HCl buffer, adjust the pH with hydrochloric acid to obtain dopamine Tris buffer solution; Step e: Place the anion exchange membrane obtained in step c in a dopamine Tris buffer solution, add copper sulfate, and stir the reaction while maintaining air circulation. After the reaction is complete, the modified anion exchange membrane is obtained.

2. The process method according to claim 1, characterized in that, The linear polymer mentioned in step a is selected from at least one of polyethylene, polypropylene, polyvinyl chloride or polyvinylidene fluoride; the organic solvent is selected from at least one of dichloromethane, dichloroethane or chloroform.

3. The process method according to claim 1, characterized in that, The temperature of the stirring reaction in step a is 50–90°C, and the stirring reaction time is 0.5–6 h.

4. The process method according to claim 1, characterized in that, The amount of organic solvent added in step b is 0.5 to 1 times the amount of organic solvent used in step a; the mass-volume concentration of anhydrous zinc chloride and organic solvent is 15 to 30 mg / mL, and the volume ratio of chloromethyl ether to organic solvent is 0.5:1 to 2:1; the temperature of the stirring reaction in step b is 30 to 55°C, and the stirring reaction time is 2 to 24 h.

5. The process method according to claim 1, characterized in that, In step c, the mass-volume concentration of the chloromethylated polymer and N,N-dimethylformamide is 15–40 mg / mL; the trimethylamine gas is obtained by heating and vaporizing an aqueous trimethylamine solution and then drying it with an alkaline drying agent; the quaternization reaction time is 10–120 minutes.

6. The process method according to claim 1, characterized in that, The mass concentration of dopamine in the solution formed in step d is 0.4–4 g / L, and the pH is adjusted to 8–9 by hydrochloric acid; in step e, copper sulfate is added to make its concentration 1–20 mmol / L, and the reaction is stirred for 1–12 h.

7. The process method according to claim 1, characterized in that, The softening adjustment unit softens the material by removing hardness, using a combination of sodium hydroxide and sodium carbonate. Sodium hydroxide is added at 1 to 4 times the mass concentration of magnesium ions, and sodium carbonate is added at 1 to 3 times the mass concentration of calcium ions. The pH adjustment range is 6 to 9.

8. The process method according to claim 1, characterized in that, The electrodialysis I and electrodialysis II treatment times are 0.5–3 hours, and the current density is 1–80 mA / cm². 2 .

9. The process method according to claim 1, characterized in that, The aerobic biochemical bacteria are salt-tolerant bacteria, and the process is fully aerobic, selected from one of the following processes: BAF, MBR, contact oxidation tank, and MBBR.

10. The process method according to claim 1, characterized in that, In the ozone catalytic oxidation process, the amount of ozone used is 0.1 to 2 times the amount of oxidant required based on the COD value of the wastewater, and the reaction time is 10 to 120 minutes.

11. The process method according to claim 1, characterized in that, The dissolved oxygen in the anaerobic biological treatment is controlled below 0.1 mg / L, the hydraulic retention time is controlled between 2 and 96 h, and the water temperature is controlled between 25 and 38 °C.

12. The process method according to claim 1, characterized in that, The methane purification process employs one of the following technologies: solid desulfurizing agent adsorption, biological desulfurization, alkaline desulfurization, or amine desulfurization, to purify the gas produced by anaerobic biochemical processes, thereby obtaining methane with a purity greater than 96%.

13. The process method according to claim 1, characterized in that, The secondary biochemical process employs one of the following processes: A / O, BAF, MBR, SBR, contact oxidation tank, and MBBR.

14. The process method according to claim 1, characterized in that, The medium- and high-pressure reverse osmosis is multi-stage, consisting of multiple medium- and high-pressure reverse osmosis membrane modules, with an operating pressure between 2.0 and 4.2 MPa. It can concentrate the salinity of wastewater to 40 to 110 g / L, with an overall concentration factor of 2 to 10. The low-pressure reverse osmosis is single-stage, with an operating pressure of 1.0 to 2.0 MPa and a water production rate of 50% to 80%.

15. The process method according to claim 1, characterized in that, The bioreactor uses BAF or MBR technology, and the bacterial strains used are salt-tolerant bacteria.

16. The process method according to claim 1, characterized in that, The water production rate of nanofiltration I is 40%–75%, and that of nanofiltration II is 30%–65%.

17. The process method according to claim 1, characterized in that, The salt crystallizer operates at a temperature of 35–60°C. In addition to obtaining sodium chloride product and concentrated mother liquor, the concentrated mother liquor is returned to electrodialysis II for secondary treatment when the sodium sulfate concentration reaches 300 g / L.

18. The process method according to claim 1, characterized in that, The operating temperature of the cryo-crystallizer is controlled between 1 and 10°C to obtain sodium sulfate decahydrate product and concentrated mother liquor. When the sodium chloride concentration of the concentrated mother liquor reaches 250 g / L, it is returned to electrodialysis II for secondary treatment.

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