A high-efficiency treatment process for salt-containing industrial wastewater

Abstract

The application discloses a kind of efficient treatment process for salt-containing industrial wastewater, it is related to wastewater treatment technical field, salt-containing industrial wastewater is sequentially through conditioning tank, silicon-removing and hardness-removing unit, biochemical unit, secondary sedimentation tank, fluoride-removing unit, filtration unit, ozone catalytic oxidation unit, moving bed biological membrane reactor processing unit, powder carbon precipitation unit and ultrafiltration-RO double membrane unit processing, water production is reused, concentrated water enters evaporation concentration unit;The silicon-removing and hardness-removing unit is treated to wastewater by adding flocculant and composite coagulant aid;The flocculant is chitosan-based flocculant, and the addition amount of flocculant is 10-20mg / L;The composite coagulant aid is composed of magnesium-aluminum hydrotalcite coagulant aid and alginic acid-silicate hybrid microgel according to the mass ratio of 2:1-4, and the addition amount of composite coagulant aid is 5-15mg / L.The application significantly improves the treatment effect of salt-containing industrial wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, and particularly relates to a high-efficiency treatment process for salt-containing industrial wastewater. BACKGROUND

[0002] Salt-containing industrial wastewater widely exists in chemical industry, electroplating, electronics, pharmaceuticals and sugar manufacturing industries, and the water quality thereof usually contains high concentrations of calcium and magnesium ions, silicates, fluorides, organic matters and trace heavy metal ions. The water quality of such wastewater is complex and the salt content is high, and direct discharge or simple treatment will cause water eutrophication, scaling, equipment corrosion and even affect the safety of downstream industrial water.

[0003] Therefore, how to efficiently, stably and economically treat salt-containing industrial wastewater is a technical problem to be solved in the field. SUMMARY

[0004] Based on the technical problems in the background art, the present application provides a high-efficiency treatment process for salt-containing industrial wastewater, which significantly improves the treatment effect of salt-containing industrial wastewater.

[0005] The high-efficiency treatment process for salt-containing industrial wastewater provided by the present application comprises the following steps: the salt-containing industrial wastewater is sequentially subjected to a conditioning tank, a silicate and hardness removal unit, a biochemical unit, a secondary sedimentation tank, a fluoride removal unit, a filtration unit, an ozone catalytic oxidation unit, a moving bed biofilm reactor treatment unit, a powdered carbon precipitation unit and an ultrafiltration-reverse osmosis double membrane unit, the produced water is reused, and the concentrated water is subjected to an evaporation and concentration unit.

[0006] The silicate and hardness removal unit is used for treating the wastewater by adding a flocculant and a composite coagulant.

[0007] The flocculant is a chitosan-based flocculant, and the addition amount of the flocculant is 10-20 mg / L.

[0008] The composite coagulant is composed of a magnesium-aluminum hydrotalcite coagulant and a seaweed acid-silicate hybrid microgel at a mass ratio of 2:1-4, and the addition amount of the composite coagulant is 5-15 mg / L.

[0009] Preferably, the preparation method of the chitosan-based flocculant is as follows:

[0010] S11: carboxymethyl chitosan is dissolved in an ice acetic acid aqueous solution, glycidol trimethylammonium chloride is then added, and the reaction is carried out at 55-65 DEG C for 4-8 h; after the reaction, filtration, washing and drying are carried out to obtain quaternary ammonium chitosan;

[0011] S12: the quaternary ammonium chitosan is dissolved in an ice acetic acid aqueous solution, acrylamide, dimethyl diallyl ammonium chloride, ammonium persulfate and ascorbic acid are then added, and the reaction is carried out at 50-60 DEG C for 2-4 h under an inert atmosphere to obtain the chitosan-based flocculant.

[0012] Preferably, the mass ratio of carboxymethyl chitosan and glycidyltrimethylammonium chloride in S11 is 1:1-2.

[0013] Preferably, the mass ratio of quaternary ammonium chitosan, acrylamide, dimethyl diallyl ammonium chloride, ammonium persulfate and ascorbic acid in S12 is 1:2-3:1-2:0.01-0.03:0.005-0.015.

[0014] Preferably, the preparation method of magnesium aluminum hydrotalcite coagulant is as follows: MgCl2·6H2O and AlCl3·6H2O are dissolved in deionized water under an inert atmosphere, and sodium hydroxide and sodium carbonate are added and reacted at 55-65°C for 8-16h to obtain magnesium aluminum hydrotalcite coagulant.

[0015] Preferably, the mass ratio of MgCl2·6H2O, AlCl3·6H2O, sodium hydroxide and sodium carbonate is 1:0.3-0.5:0.8-1.2:0.4-0.5.

[0016] Preferably, the preparation method of alginate-silicate hybrid microgel is as follows:

[0017] S21: Sodium alginate is dissolved in deionized water, 2,3-epoxypropyltrimethylammonium chloride is added and reacted at 60-70°C under alkaline conditions for 3-5h, and after reaction, filtration, washing and drying, quaternary ammonium sodium alginate is prepared;

[0018] S22: Quaternary ammonium sodium alginate is dissolved in hydrochloric acid, tetraethoxysilane and ammonia are added and stirred at room temperature for 1-3h, and then glutaraldehyde is added and reacted for 20-40min to obtain alginate-silicate hybrid microgel.

[0019] Preferably, the mass ratio of sodium alginate and 2,3-epoxypropyltrimethylammonium chloride in S21 is 1:0.5-1.

[0020] Preferably, the mass ratio of quaternary ammonium sodium alginate and tetraethoxysilane in S22 is 1:1-2.

[0021] Preferably, a scale inhibitor with a mass fraction of 20-40mg / L is further added to the reverse osmosis system in the ultrafiltration-reverse osmosis double membrane unit, and the scale inhibitor is composed of sodium carboxymethyl cellulose, itaconic acid-sodium methacrylsulfonate and modified polyepoxysuccinic acid with a mass ratio of 1:0.4-0.6:0.4-0.6.

[0022] Preferably, the preparation method of modified polyepoxysuccinic acid is as follows: polyepoxysuccinic acid is dissolved in deionized water, 2-phospho-1,2,4-butane tricarboxylic acid is added under alkaline conditions, and reacted at 85-95°C for 2-4h, and then histidine is added and reacted for 1-3h to obtain modified polyepoxysuccinic acid.

[0023] Preferably, the mass-volume ratio of polyepoxysuccinic acid, 2-phospho-1,2,4-tricarboxylic acid butane and arginine is 1g:0.5-1ml:0.05-0.15g.

[0024] The beneficial technical effects of the present application are:

[0025] (1) In the silicon and hardness removal stage, the present application uses the synergistic effect of chitosan-based flocculants and composite coagulant aids to greatly improve the removal efficiency of silicate, calcium and magnesium ions in wastewater. The chitosan-based flocculants adsorb negatively charged colloids and suspended solids in water through their cationic structure, and promote the formation of micro-flocs; while the composite coagulant aid is composed of magnesium-aluminum hydrotalcite and alginate-silicate hybrid microgel, which can adsorb free ions and induce micro-floc aggregation through the coordination of porous layered structure and carboxyl / quaternary ammonium groups; in this process, the coagulant aid not only improves the adsorption capacity of the flocculant, but also promotes the rapid nucleation and growth of the flocs, making the floc density increase, the particle size larger, and the settling speed faster, thereby significantly reducing the load of the secondary sedimentation tank and subsequent membrane unit; the synergistic regulation of the composite coagulant aid in spatial structure and surface chemistry makes the micro-flocs generated by the flocculant more easily aggregated and the settling more uniform, thereby effectively improving the stability and efficiency of wastewater treatment.

[0026] (2) In the membrane treatment stage, the scale inhibitor introduced in the ultrafiltration-reverse osmosis double membrane system of the present application is composed of sodium carboxymethyl cellulose, itaconic acid-sodium methacrylsulfonate and modified polyepoxysuccinic acid, which form a stable scale inhibition network through synergistic effect, significantly delaying the deposition of calcium and magnesium hardness salts and silicates on the membrane surface, and the synergistic effect is reflected in the multidimensional regulation of scale inhibition mechanism, not only preventing crystal formation, but also reducing crystal adhesion. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A flow chart of a high-efficiency treatment process for salt-containing industrial wastewater is proposed for the present application. DETAILED DESCRIPTION

[0028] The present application will be further illustrated below in conjunction with specific examples. Example 1

[0029] The salt-containing industrial wastewater of a factory in an industrial park is first introduced into a regulating tank, and the water quality is homogenized by a stirring and aeration device. The adjusted wastewater is first lifted into a silicon and hardness removal unit by a lifting pump, and the silicon and hardness in the wastewater are removed by adding flocculants and coagulants through a coagulation sedimentation and filtration method. The effluent after the silicon and hardness removal enters a biochemical unit, and a multi-stage A / O process is used to remove the ammonia nitrogen, total nitrogen, organic matter and other water pollutants in the wastewater. The effluent of the biochemical unit is separated from the sludge in a radial flow secondary sedimentation tank. The effluent of the secondary sedimentation tank enters a fluorine removal unit through an intermediate lifting pump, and a fluorine removal agent (an existing fluorine removal agent for wastewater treatment) is used to remove the fluorine ions in the water to reduce the influence of the fluorine ions on the subsequent membrane system. The effluent is treated by a filtration unit (V-type filter tank) and then enters an ozone catalytic oxidation unit. The ozone catalytic oxidation unit uses two-stage catalysis to mainly remove the refractory organic matter in the wastewater by hydroxyl radical oxidation of the refractory organic matter or to improve the biodegradability of the wastewater. The wastewater treated by the ozone catalytic oxidation unit enters a moving bed biofilm reactor (MBBR) treatment unit to further remove the organic matter in the water by a biofilm technology. After the wastewater is treated by the MBBR treatment unit, it enters a powdered carbon sedimentation tank for emergency treatment to deal with the over-standard organic matter in special situations. After the wastewater passes through the powdered carbon tank, it enters an ultrafiltration-reverse osmosis double membrane unit. The product water after the membrane separation of the ultrafiltration-reverse osmosis double membrane unit is reused, and the concentrated water enters an evaporation and concentration unit.

[0030] The flocculant is a chitosan-based flocculant, and the addition amount of the flocculant is 15 mg / L.

[0031] The composite coagulant is composed of magnesium-aluminum hydrotalcite coagulant and alginate-silicate hybrid microgel at a mass ratio of 1:1, and the addition amount of the composite coagulant (dry basis) is 10 mg / L. The solid content of the magnesium-aluminum hydrotalcite coagulant and the alginate-silicate hybrid microgel is controlled to be 10%.

[0032] The preparation method of the chitosan-based flocculant is as follows:

[0033] S11: Dissolve carboxymethyl chitosan in an ice acetic acid aqueous solution, then add glycidyltrimethylammonium chloride, and react at 60℃ for 6h. After the reaction, filter, wash and dry to obtain quaternized chitosan.

[0034] S12: Dissolve the quaternized chitosan in an ice acetic acid aqueous solution, then add acrylamide, dimethyldiallylammonium chloride, ammonium persulfate and ascorbic acid, and react at 55℃ for 3h under an inert atmosphere to obtain the chitosan-based flocculant.

[0035] The mass ratio of carboxymethyl chitosan to glycidyltrimethylammonium chloride in S11 is 1:1.5.

[0036] The mass ratio of quaternary ammonium chitosan, acrylamide, dimethyl diallyl ammonium chloride, ammonium persulfate and ascorbic acid in S12 is 1:2.5:1.5:0.02:0.01.

[0037] The preparation method of the magnesium-aluminum hydrotalcite coagulant aid is as follows: MgCl2·6H2O and AlCl3·6H2O are dissolved in deionized water under an inert atmosphere, and then sodium hydroxide and sodium carbonate are added, and the reaction is carried out at 60°C for 12h to obtain the magnesium-aluminum hydrotalcite coagulant aid.

[0038] The mass ratio of MgCl2·6H2O, AlCl3·6H2O, sodium hydroxide and sodium carbonate is 1:0.4:1:0.45.

[0039] The preparation method of the alginate-silicate hybrid microgel is as follows:

[0040] S21: Sodium alginate is dissolved in deionized water, 2,3-epoxypropyl trimethyl ammonium chloride is added, and the reaction is carried out at 65°C under alkaline conditions for 4h, and then filtration, washing and drying are carried out after the reaction to obtain quaternary ammonium sodium alginate;

[0041] S22: Quaternary ammonium sodium alginate is dissolved in hydrochloric acid, tetraethoxysilane and ammonia water are added, stirring at room temperature for 2h, and then glutaraldehyde is added and the reaction is continued for 30min to obtain alginate-silicate hybrid microgel.

[0042] The mass ratio of sodium alginate and 2,3-epoxypropyl trimethyl ammonium chloride in S21 is 1:0.8.

[0043] The mass ratio of quaternary ammonium sodium alginate and tetraethoxysilane in S22 is 1:1.5.

[0044] In the reverse osmosis system in the ultrafiltration-reverse osmosis double membrane unit, 30mg / L of scale inhibitor is also added, and the scale inhibitor is composed of carboxymethyl cellulose sodium, itaconic acid-methyl methacrylate sulfonic acid sodium and modified polyepoxysuccinic acid with a mass ratio of 1:0.5:0.5.

[0045] The preparation method of the modified polyepoxysuccinic acid is as follows: polyepoxysuccinic acid is dissolved in deionized water, 2-phospho-1,2,4-tricarboxylic acid butane is added under alkaline conditions, and the reaction is carried out at 90°C for 3h, and then histidine is added and the reaction is continued for 2h to obtain the modified polyepoxysuccinic acid.

[0046] The mass volume ratio of polyepoxysuccinic acid, 2-phospho-1,2,4-tricarboxylic acid butane and histidine is 1g:0.8ml:0.1g.

[0047] The content of each substance in the effluent after treatment of each unit is determined, and the test results are shown in Table 1.

[0048] Table 1 Sewage treatment effect

[0049]

[0050] Example 2

[0051] In this example, the flocculant is a chitosan-based flocculant, and the addition amount of the flocculant is 10 mg / L.

[0052] The composite coagulant is composed of a magnesium-aluminum hydrotalcite coagulant and a sodium alginate-silicate hybrid microgel at a mass ratio of 2:1, and the addition amount of the composite coagulant (calculated on a dry basis) is 5 mg / L. The solid content of the magnesium-aluminum hydrotalcite coagulant and the sodium alginate-silicate hybrid microgel is controlled to be 10%.

[0053] The preparation method of the chitosan-based flocculant is as follows:

[0054] S11: Dissolve carboxymethyl chitosan in an ice acetic acid aqueous solution, then add glycidyl trimethylammonium chloride, and react at 55°C for 8h. After the reaction, filter, wash and dry to obtain quaternized chitosan.

[0055] S12: Dissolve the quaternized chitosan in an ice acetic acid aqueous solution, then add acrylamide, dimethyl diallyl ammonium chloride, ammonium persulfate and ascorbic acid, and react at 50°C for 4h under an inert atmosphere to obtain the chitosan-based flocculant.

[0056] The mass ratio of carboxymethyl chitosan to glycidyl trimethylammonium chloride in S11 is 1:1.

[0057] The mass ratio of quaternized chitosan, acrylamide, dimethyl diallyl ammonium chloride, ammonium persulfate and ascorbic acid in S12 is 1:2:1:0.01:0.005.

[0058] The preparation method of the magnesium-aluminum hydrotalcite coagulant is as follows: under an inert atmosphere, dissolve MgCl2·6H2O and AlCl3·6H2O in deionized water, then add sodium hydroxide and sodium carbonate, and react at 55°C for 16h to obtain the magnesium-aluminum hydrotalcite coagulant.

[0059] The mass ratio of MgCl2·6H2O, AlCl3·6H2O, sodium hydroxide and sodium carbonate is 1:0.3:0.8:0.4.

[0060] The preparation method of the sodium alginate-silicate hybrid microgel is as follows:

[0061] S21: Dissolve sodium alginate in deionized water, then add 2,3-epoxypropyl trimethylammonium chloride under alkaline conditions and react at 60°C for 5h. After the reaction, filter, wash and dry to obtain quaternized sodium alginate.

[0062] S22: The quaternary ammonium sodium alginate is dissolved in hydrochloric acid, tetraethoxysilane and ammonia water are added, and stirring is carried out at room temperature for 1 h, then glutaraldehyde is added and the reaction is continued for 20 min to prepare the alginate-silicate hybrid microgel.

[0063] The mass ratio of sodium alginate to 2,3-epoxypropyl trimethyl ammonium chloride in S21 is 1:0.5.

[0064] The mass ratio of quaternary ammonium sodium alginate to tetraethoxysilane in S22 is 1:1.

[0065] The reverse osmosis system in the ultrafiltration-reverse osmosis double membrane unit is additionally added with 20 mg / L of scale inhibitor, and the scale inhibitor is composed of sodium carboxymethyl cellulose, itaconic acid-sodium methallyl sulfonate and modified polyepoxysuccinic acid in a mass ratio of 1:0.4:0.4.

[0066] The preparation method of the modified polyepoxysuccinic acid is as follows: polyepoxysuccinic acid is dissolved in deionized water, 2-phospho-1,2,4-butane tricarboxylic acid is added under alkaline conditions, and the reaction is carried out at 85℃ for 4 h, then histidine is added and the reaction is continued for 1 h to prepare the modified polyepoxysuccinic acid.

[0067] The mass-volume ratio of polyepoxysuccinic acid, 2-phospho-1,2,4-butane tricarboxylic acid and histidine is 1 g:0.5 ml:0.05 g.

[0068] The remaining conditions are the same as those in Example 1. Example 3

[0069] In this example, the flocculant is a chitosan-based flocculant, and the addition amount of the flocculant is 20 mg / L.

[0070] The composite coagulant is composed of magnesium-aluminum hydrotalcite coagulant and alginate-silicate hybrid microgel in a mass ratio of 1:2, and the addition amount (dry basis) of the composite coagulant is 15 mg / L, and the solid content of the magnesium-aluminum hydrotalcite coagulant and the alginate-silicate hybrid microgel is controlled to be 10%.

[0071] The preparation method of the chitosan-based flocculant is as follows:

[0072] S11: Carboxymethyl chitosan is dissolved in an aqueous glacial acetic acid solution, then glycidyl trimethyl ammonium chloride is added, and the reaction is carried out at 65℃ for 4 h, after the reaction, filtration, washing and drying are carried out to prepare quaternary ammonium chitosan.

[0073] S12: Quaternary ammonium chitosan is dissolved in an aqueous glacial acetic acid solution, then acrylamide, dimethyl diallyl ammonium chloride, ammonium persulfate and ascorbic acid are added, and the reaction is carried out at 60℃ for 2 h under an inert atmosphere to prepare the chitosan-based flocculant.

[0074] The mass ratio of carboxymethyl chitosan and glycidyltrimethylammonium chloride in S11 is 1:2.

[0075] The mass ratio of quaternary ammonium chitosan, acrylamide, dimethyl diallyl ammonium chloride, ammonium persulfate and ascorbic acid in S12 is 1:3:2:0.03:0.015.

[0076] The preparation method of the magnesium aluminum hydrotalcite coagulant aid is as follows: MgCl2·6H2O and AlCl3·6H2O are dissolved in deionized water under an inert atmosphere, and sodium hydroxide and sodium carbonate are added to react at 65℃ for 8h to obtain the magnesium aluminum hydrotalcite coagulant aid.

[0077] The mass ratio of MgCl2·6H2O, AlCl3·6H2O, sodium hydroxide and sodium carbonate is 1:0.5:1.2:0.5.

[0078] The preparation method of the alginate-silicate hybrid microgel is as follows:

[0079] S21: Sodium alginate is dissolved in deionized water, 2,3-epoxypropyltrimethylammonium chloride is added, and the reaction is carried out at 70℃ under alkaline conditions for 3h, and after the reaction, filtration, washing and drying are carried out to obtain quaternary ammonium sodium alginate;

[0080] S22: Quaternary ammonium sodium alginate is dissolved in hydrochloric acid, tetraethoxysilane and ammonia water are added and stirred at room temperature for 3h, and then glutaraldehyde is added and reacted for 40min to obtain alginate-silicate hybrid microgel.

[0081] The mass ratio of sodium alginate and 2,3-epoxypropyltrimethylammonium chloride in S21 is 1:1.

[0082] The mass ratio of quaternary ammonium sodium alginate and tetraethoxysilane in S22 is 1:2.

[0083] In the reverse osmosis system in the ultrafiltration-reverse osmosis double membrane unit, 40mg / L of scale inhibitor is also added, and the scale inhibitor is composed of sodium carboxymethyl cellulose, itaconic acid-sodium methacrylsulfonate and modified polyepoxysuccinic acid in a mass ratio of 1:0.6:0.6.

[0084] The preparation method of the modified polyepoxysuccinic acid is as follows: polyepoxysuccinic acid is dissolved in deionized water, 2-phospho-1,2,4-tricarboxylic acid butane is added under alkaline conditions, and the reaction is carried out at 95℃ for 2h, and then histidine is added and reacted for 3h to obtain the modified polyepoxysuccinic acid.

[0085] The mass volume ratio of polyepoxysuccinic acid, 2-phospho-1,2,4-tricarboxylic acid butane and histidine is 1g:1ml:0.15g.

[0086] The remaining conditions are the same as those in Example 1. Comparative Example 1

[0087] The composite coagulant of the present scheme is a magnesium-aluminum hydrotalcite coagulant, and the remaining conditions are the same as those of Example 1. Comparative Example 2

[0088] The composite coagulant of the present scheme is a magnesium-aluminum hydrotalcite coagulant, and the remaining conditions are the same as those of Example 1. Comparative Example 3

[0089] The scale inhibitor of the present scheme is composed of itaconic acid-sodium methallyl sulfonate and modified polyepoxysuccinic acid at a mass ratio of 1:1; the remaining conditions are the same as those of Example 1. Comparative Example 4

[0090] The scale inhibitor of the present scheme is composed of sodium carboxymethyl cellulose and itaconic acid-sodium methallyl sulfonate at a mass ratio of 1:0.5. The remaining conditions are the same as those of Example 1. Comparative Example 5

[0091] The scale inhibitor of the present scheme is composed of sodium carboxymethyl cellulose and modified polyepoxysuccinic acid at a mass ratio of 1:0.5; the remaining conditions are the same as those of Example 1.

[0092] The contents of various substances in the effluent of the desilication and hardness removal unit in Comparative Examples 1-2 were determined, and the test results are shown in Table 2.

[0093] Table 2 Determination results of contents of various substances in effluent of desilication and hardness removal unit

[0094]

[0095] As can be seen from the test results in Table 2, in the desilication and hardness removal stage, the present application uses the synergistic effect of chitosan-based flocculant and composite coagulant to greatly improve the removal efficiency of silicate, calcium and magnesium ions in wastewater. The chitosan-based flocculant adsorbs negatively charged colloids and suspended solids in water through its cationic structure, and at the same time promotes the formation of micro-flocs; while the composite coagulant is composed of magnesium-aluminum hydrotalcite and alginate-silicate hybrid microgel, which can adsorb free ions and induce micro-floc aggregation through the complexation of porous layered structure and carboxyl / quaternary ammonium groups; in this process, the coagulant not only improves the adsorption capacity of the flocculant, but also promotes the rapid nucleation and growth of the flocs, making the floc density increase, the particle size larger and the settling speed faster, thereby significantly reducing the load of the secondary sedimentation tank and subsequent membrane unit; the synergistic regulation of the composite coagulant in spatial structure and surface chemistry makes the micro-flocs generated by the flocculant more easily aggregated and the settling more uniform, thereby effectively improving the stability and efficiency of wastewater treatment.

[0096] In addition, the scale inhibition performance of the scale inhibitors of Example 1 and Comparative Examples 3-5 was determined according to GB / T16632-2019, and the test results are shown in Table 3.

[0097] Table 3 Scale inhibitor scale inhibition performance

[0098]

[0099] As can be seen from the experimental results in Table 3, the scale inhibitor introduced in the ultrafiltration-reverse osmosis double membrane system of the present application is composed of sodium carboxymethyl cellulose, itaconic acid-sodium methacrylsulfonate and modified polyepoxysuccinic acid, which has a synergistic effect in improving the scale inhibition effect, because the three components form a stable scale inhibition network through synergistic effect, significantly delaying the deposition of calcium magnesium hardness salt and silicate on the membrane surface, and the synergistic effect is reflected in the multidimensional regulation of the scale inhibition mechanism, not only preventing crystal formation, but also reducing crystal adhesion.

[0100] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the present application, the scope of the present application is defined by the appended claims and their equivalents, and all should be included within the protection scope of the present application.

Claims

1. A process for efficient treatment of salt containing industrial wastewater, characterized in that, The salt-containing industrial wastewater is sequentially treated by a conditioning tank, a silicon and hardness removal unit, a biochemical unit, a secondary sedimentation tank, a fluorine removal unit, a filtration unit, an ozone catalytic oxidation unit, a moving bed biofilm reactor treatment unit, a powdered carbon precipitation unit and an ultrafiltration-reverse osmosis double membrane unit, the produced water is reused, and the concentrated water is introduced into an evaporation concentration unit; The silicon and hardness removal unit is used for treating the wastewater by adding a flocculant and a composite coagulant; The flocculant is a chitosan-based flocculant, and the addition amount of the flocculant is 10-20 mg / L; The composite coagulant is composed of a magnesium-aluminum hydrotalcite coagulant and a sodium alginate-silicate hybrid microgel at a mass ratio of 2:1-4, and the addition amount of the composite coagulant is 5-15 mg / L; The preparation method of the sodium alginate-silicate hybrid microgel is as follows: S21: sodium alginate is dissolved in deionized water, 2,3-epoxypropyl trimethylammonium chloride is added, and the reaction is carried out at 60-70 DEG C under alkaline conditions for 3-5 h, and after the reaction, filtration, washing and drying are carried out to prepare quaternary ammonium sodium alginate; wherein the mass ratio of sodium alginate and 2,3-epoxypropyl trimethylammonium chloride is 1:0.5-1; S22: quaternary ammonium sodium alginate is dissolved in hydrochloric acid, tetraethoxysilane and ammonia water are added, stirring is carried out at room temperature for 1-3 h, then glutaraldehyde is added and the reaction is continued for 20-40 min to prepare a sodium alginate-silicate hybrid microgel; wherein the mass ratio of quaternary ammonium sodium alginate and tetraethoxysilane is 1:1-2; The reverse osmosis system in the ultrafiltration-reverse osmosis double membrane unit further adds a scale inhibitor at 20-40 mg / L, and the scale inhibitor is composed of carboxymethyl cellulose sodium, itaconic acid-methyl methacrylate sulfonic acid sodium and modified polyepoxysuccinic acid at a mass ratio of 1:0.4-0.6:0.4-0.6; The preparation method of the modified polyepoxysuccinic acid is as follows: polyepoxysuccinic acid is dissolved in deionized water, 2-phospho-1,2,4-tricarboxylic acid butane is added under alkaline conditions, the reaction is carried out at 85-95 DEG C for 2-4 h, then histidine is added and the reaction is continued for 1-3 h to prepare the modified polyepoxysuccinic acid; The mass-volume ratio of polyepoxysuccinic acid, 2-phospho-1,2,4-tricarboxylic acid butane and histidine is 1 g:0.5-1 ml:0.05-0.15 g.

2. A process for efficient treatment of salt containing industrial wastewater as claimed in claim 1 wherein, The preparation method of the chitosan-based flocculant is as follows: S11: carboxymethyl chitosan is dissolved in an ice acetic acid aqueous solution, then glycidyl trimethylammonium chloride is added and the reaction is carried out at 55-65 DEG C for 4-8 h, and after the reaction, filtration, washing and drying are carried out to prepare quaternary ammonium chitosan; S12: quaternary ammonium chitosan is dissolved in an ice acetic acid aqueous solution, then acrylamide, dimethyl diallyl ammonium chloride, ammonium persulfate and ascorbic acid are added, the reaction is carried out at 50-60 DEG C under an inert atmosphere for 2-4 h to prepare the chitosan-based flocculant.

3. A process for efficient treatment of salt containing industrial wastewater as claimed in claim 2 wherein, The mass ratio of carboxymethyl chitosan and glycidyl trimethylammonium chloride in S11 is 1:1-2; The mass ratio of quaternary ammonium chitosan, acrylamide, dimethyl diallyl ammonium chloride, ammonium persulfate and ascorbic acid in S12 is 1:2-3:1-2:0.01-0.03:0.005-0.

015.

4. A process for efficient treatment of salt containing industrial wastewater as claimed in claim 1, wherein, The preparation method of the magnesium-aluminum hydrotalcite coagulant is as follows: MgCl2.6H2O and AlCl3.6H2O are dissolved in deionized water under inert atmosphere, and then sodium hydroxide and sodium carbonate are added, and the reaction is carried out at 55-65 DEG C for 8-16 h to obtain the magnesium-aluminum hydrotalcite coagulant.

5. A process for efficient treatment of salt containing industrial wastewater as claimed in claim 4 wherein, The mass ratio of MgCl2.6H2O, AlCl3.6H2O, sodium hydroxide and sodium carbonate is 1:0.3-0.5:0.8-1.2:0.4-0.5.

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