Wastewater resource recovery zero-discharge device and method

Abstract

The present invention relates to the technical field of zero-discharge of wastewater resources. The zero-discharge device for wastewater resources includes flocculation and precipitation of impure salts, addition of soda ash to obtain calcium carbonate precipitation, addition of caustic soda to obtain magnesium hydroxide, membrane filtration, pH value adjustment, ion exchange softening, advanced oxidation, biofilm biochemistry, membrane filter, nanofiltration, addition of lime milk to nanofiltration intercepted water to obtain calcium sulfate, and reflux of supernatant to the impure salt precipitation tank, nanofiltration permeate water is concentrated by reverse osmosis A and then concentrated by a brine concentrator, and the brine concentrator fresh water is concentrated by reverse osmosis B and refluxed to the brine concentrator, and the brine concentrator concentrated water enters the evaporation crystallization device, and then obtains sodium chloride and sodium nitrate respectively by heat separation and cold separation, and most of the crystallization mother liquor is refluxed for treatment, and a small part is dried for treatment; reverse osmosis produced water and distilled water are reused. The present invention recovers commercial calcium carbonate, magnesium hydroxide, calcium sulfate, sodium chloride, sodium nitrate salts and high-quality recycled water, with less solid waste discharge and low operating costs.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and relates to a liquid zero-discharge method for obtaining recycled water by sewage treatment and crystallizing and separating main salts in the water. Background Art

[0002] As human economic activities intensify, water resources will inevitably become a bottleneck for economic development. Therefore, in more and more cases, sewage needs to be regenerated into recycled water that can replace raw water; in some cases, zero liquid discharge needs to be achieved.

[0003] Common recycled water technology is to perform flocculation sedimentation, ultrafiltration, and reverse osmosis treatment on sewage after traditional biochemical treatment or other sewage with low organic pollution. The main problem at present is that due to the lack of in-depth treatment of organic pollutants before entering the membrane system, organic pollutants in the water are still at a high level, reverse osmosis cleaning is frequent, and reverse osmosis concentrated water cannot meet the discharge standards.

[0004] Liquid zero-discharge sewage treatment methods generally include sewage chemical softening and flocculation precipitation, ultrafiltration, reverse osmosis, concentrated water reverse osmosis, brine concentration and evaporation crystallization devices, among which brine brine concentration devices include electrodialysis, steam mechanical compression evaporator, forward osmosis, membrane distillation, high-pressure reverse osmosis, etc. The main problem at present is that due to the lack of in-depth treatment of organic pollutants before entering the membrane system, the reverse osmosis membrane needs frequent chemical cleaning. Similarly, due to the lack of in-depth treatment of organic pollutants before entering the membrane system, the organic content in the reverse osmosis concentrated water is too high, making the concentrated water evaporation and crystallization difficult. Evaporation and crystallization obtains a large amount of mixed salts and mixed salt mixtures of organic pollutants. Most of this mixed salt mixture dissolves in water, and improper treatment will cause environmental pollution again; therefore, the further treatment cost of the main mixture is high, and it even needs to be treated as hazardous waste.

[0005] The Chinese patent application (201510522599.X) focuses on solving the problem of organic interference in the zero-discharge process of sewage, but does not recover insoluble salts, resulting in too high a volume of chemical sludge; sodium sulfate is obtained by evaporation and crystallization, which increases the evaporation and crystallization processing capacity, but the obtained sodium sulfate crystals containing crystallization water have almost no reuse value, increasing the processing cost.

[0006] The main cations in common sewage are sodium, calcium, and magnesium, and the main anions are chloride, sulfate, nitrate, and bicarbonate. There are also small amounts of potassium, fluoride, and phosphate ions. The purpose of this sewage resource zero-discharge device and treatment method is to recycle and resource all the main cations and anions in the water, while reducing the total amount of solid waste and operating costs. Summary of the invention

[0007] The present invention aims to solve the technical problems that the reverse osmosis cleaning of recycled water technology is frequent and the reverse osmosis concentrated water cannot meet the discharge standards; the reverse osmosis membrane in the liquid zero-discharge sewage treatment method needs frequent chemical cleaning, the concentrated water evaporation and crystallization operation is difficult, and the evaporation and crystallization obtains a large amount of mixed salts and organic pollutants. The whole system is difficult to operate stably for a long time, the salt recovery rate is low, the amount of chemical sludge is large, and the operating cost is high.

[0008] In order to achieve the above objectives, the present invention discloses a wastewater resource zero-discharge treatment device, which comprises, in sequence, a flocculant adding device, a coagulant aid adding device, a salt precipitation tank, a soda ash adding device, a calcium carbonate precipitation tank, a caustic soda adding device, a magnesium hydroxide precipitation tank, an acid adding device, a cation exchanger, an oxidant adding device, an oxidation contactor, a biofilm reactor and a blower, a membrane filter B, a nanofiltration membrane separator, a brine concentrator, an evaporation crystallization device, a hot separator, a cold separator, and a mother liquor dryer; it also comprises a cation exchanger regeneration wastewater return pipe for returning the cation exchanger regeneration wastewater to the salt precipitation tank, a membrane filter B wastewater return pipe for returning the membrane filter B wastewater to the salt precipitation tank, and a mother liquor dryer for treating the wastewater. A calcium sulfate precipitation tank for the retained water of the nanofiltration membrane separator, a nanofiltration concentrated water reflux pipeline for returning the retained water of the nanofiltration membrane separator to the calcium sulfate precipitation tank, and a lime milk adding device for adding lime to the retained water of the nanofiltration membrane separator; a calcium sulfate precipitation tank produced water reflux pipeline for returning the produced water of the calcium sulfate precipitation tank to the mixed salt precipitation tank, a reverse osmosis B concentrated water reflux pipeline for returning the concentrated water of the reverse osmosis separator B to the brine concentrator, a mother liquor reflux crystallizer pipeline for returning part of the crystallization mother liquor to the evaporator, and a mother liquor reflux mixed salt precipitation tank pipeline for returning part of the crystallization mother liquor to the mixed salt precipitation tank; it also includes multiple sediment filter pressing and drying devices, multiple membrane backwashing and chemical cleaning devices, at least one cation exchanger regeneration device, multiple lifting pumps and automatic control devices.

[0009] A membrane filter A and a membrane filter A wastewater return pipeline for returning the wastewater of the membrane filter A to the mixed salt precipitation tank are also included between the magnesium hydroxide precipitation tank and the cation exchanger.

[0010] A reverse osmosis separator A is also included between the nanofiltration membrane separator and the salt water concentrator. The concentrated water of the reverse osmosis separator A enters the salt water concentrator, and the fresh water is recycled water.

[0011] A dilution pipeline for adding recycled water is also included between the cation exchanger and the oxidation contactor.

[0012] The brine concentrator is at least one of an electrodialysis device, a steam mechanical recompression evaporator, a multiple-effect evaporator, and a single-effect evaporator.

[0013] The evaporation crystallization device is at least one of a steam mechanical recompression evaporation crystallizer, a multi-effect evaporation crystallizer, and a single-effect crystallization evaporation crystallizer.

[0014] Also in order to achieve the above-mentioned purpose, the present invention discloses a method for treating wastewater resource-based zero-discharge using the wastewater resource-based zero-discharge treatment device, comprising: adding a flocculant to the raw water through a flocculant adding device and a coagulant adding device to generate a small amount of insoluble salts containing phosphates and organic pollutants, which are precipitated in a salt precipitation tank, and the insoluble salts form solid waste; adding a slightly excess amount of soda ash (sodium carbonate) to the water produced by the salt precipitation tank through a soda ash adding device, and precipitating the generated calcium carbonate in a calcium carbonate precipitation tank to obtain calcium carbonate; adding caustic soda (sodium hydroxide) to the water produced by the calcium carbonate precipitation tank to pH = 11-12 through a caustic soda adding device, and generating magnesium hydroxide in a magnesium hydroxide precipitation tank; The magnesium hydroxide is obtained by precipitation in a sedimentation tank; the water produced by the magnesium hydroxide sedimentation tank is acidified by an acid adding device to adjust the pH value to 5-8, and enters a cation exchanger for softening; the cation exchanger regeneration wastewater is returned to the miscellaneous salt sedimentation tank through a cation exchanger regeneration wastewater return pipe; an oxidant is added to the cation exchanger produced water through an oxidant adding device, and enters an oxidation contactor to improve the biodegradability of organic pollutants through an oxidation reaction; the effluent of the oxidation contactor enters a biofilm reactor, and a biochemical degradation reaction of organic pollutants occurs; the water produced by the biofilm reactor is filtered through a membrane filter B, and the wastewater generated by the filtration of the membrane filter B is returned to the miscellaneous salt sedimentation tank through a wastewater return pipe of the membrane filter B; the membrane The water produced by filter B enters the nanofiltration membrane separator, and the retained water of the nanofiltration membrane separator is added with lime milk through the lime milk adding device. The produced calcium sulfate is precipitated in the calcium sulfate precipitation tank to obtain calcium sulfate. The water produced by the calcium sulfate precipitation tank is returned to the miscellaneous salt precipitation tank through the reflux pipeline of the calcium sulfate precipitation tank (1). The water permeated by the nanofiltration membrane separator enters the brine concentrator; the fresh water of the brine concentrator is treated by reverse osmosis B to obtain recycled water, and the concentrated water of reverse osmosis B is returned to the brine concentrator through the concentrated water reflux pipeline of reverse osmosis B; the concentrated water produced by the brine concentrator enters the evaporation crystallization device, and the steam produced by the evaporation crystallization device is obtained through the heat recovery device to obtain recycled water. The evaporation concentration is controlled so that the sodium nitrate is heated in the evaporation crystallization device. The liquid is close to saturation, and the hot mother liquor is separated by a hot separator to obtain sodium chloride. The mother liquor separated by the hot separator is cooled to initiate the sodium nitrate crystallization process, and is separated by a cold separator to obtain sodium nitrate; most of the mother liquor separated by the cold separator is refluxed to the evaporation crystallization device through the mother liquor reflux crystallizer pipeline to continue evaporation and crystallization, and the cycle is repeated; when organic pollutants and other impurities in the mother liquor affect the purity of sodium chloride and sodium nitrate, part of the mother liquor is refluxed to the miscellaneous salt precipitation tank through the mother liquor reflux miscellaneous salt precipitation tank pipeline, and most of the pollutants therein are eliminated through the miscellaneous salt precipitation tank and its subsequent processes; in order to further ensure the purity of sodium chloride and sodium nitrate, a small part of the mother liquor is dried by a mother liquor dryer to produce a mother liquor drying product.

[0015] A membrane filter A is also included between the magnesium hydroxide precipitation tank and the acid adding device. The water produced by the membrane filter A enters the cation exchanger after acid addition, and the wastewater of the membrane filter A flows back to the mixed salt precipitation tank through the wastewater return pipe of the membrane filter A.

[0016] There is a reverse osmosis separator A between the nanofiltration membrane separator and the salt water concentrator. The fresh water of the reverse osmosis separator A is recycled water, and the concentrated water of the reverse osmosis separator A enters the salt water concentrator.

[0017] The adding of the oxidant and the biochemical degradation reaction are repeated at least once.

[0018] Recycled water is added between the cation exchanger and the oxidation contactor through a dilution pipeline to adjust the salt content to less than 2%.

[0019] The beneficial effects of the present invention include degradation of most organic pollutants, stable operation of the membrane system and the evaporator, and high purity of recovered salts; recovery of five salts, namely calcium carbonate, magnesium hydroxide, calcium sulfate, sodium chloride, and sodium nitrate, and recovery of all major ions commonly found in raw water, thereby significantly reducing solid waste; obtaining high-quality recycled water; precipitating sulfate ions, reducing evaporation of concentrated brine, and reducing operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the process of sewage resource treatment.

[0021] Wherein: 1. miscellaneous salt precipitation tank, 2. calcium carbonate precipitation tank, 3. magnesium hydroxide precipitation tank, 4. membrane filter A, 5. cation exchanger, 6. oxidation contactor, 7. biofilm reactor, 8. membrane filter B, 9. nanofiltration membrane separator, 10. calcium sulfate precipitation tank, 11. reverse osmosis membrane separator A, 12. brine concentrator, 13. reverse osmosis concentrator B, 14. evaporation crystallization device, 15. hot separator, 16. cold separator, 17. mother liquor dryer;

[0022] 110. Wastewater return pipe of membrane filter A, 120. Wastewater return pipe of cation exchanger regeneration, 130. Wastewater return pipe of membrane filter B, 140. Nanofiltration concentrated water return pipe, 150. Calcium sulfate precipitation tank produced water return pipe, 160. Reverse osmosis B concentrated water return pipe, 170. Mother liquor return crystallizer pipe, 180. Mother liquor return salt precipitation tank pipe;

[0023] 210. Flocculant adding device, 220. Coagulant aid adding device, 230. Soda ash adding device, 240. Caustic soda adding device, 250. Acid adding device, 260. Oxidant adding device, 270. Blower, 280. Lime milk adding device;

[0024] 300. Raw water, 310. Recycled water, 320. Calcium carbonate, 330. Magnesium hydroxide, 340. Calcium sulfate, 350. Sodium chloride, 360. Sodium nitrate;

[0025] 410. Insoluble impurity salts, 420. Mother liquor drying product. DETAILED DESCRIPTION

[0026] like Figure 1 As shown, the wastewater resource zero-discharge treatment device comprises, in sequence, a flocculant adding device (210), a coagulant aid adding device (220), a miscellaneous salt precipitation tank (1), a soda ash adding device (230), a calcium carbonate precipitation tank (2), a caustic soda adding device (240), a magnesium hydroxide precipitation tank (3), an acid adding device (250), a cation exchanger (5), an oxidant adding device (260), an oxidation contactor (6), a biofilm reactor (7) and a blower (270), a membrane filter B (8), a nanofiltration membrane separator (9), a salt water concentrator (12), an evaporation crystallization device (14), a hot separator (15), a cold separator (16), and a mother liquor dryer (17); and also includes a cation exchanger regeneration wastewater return pipe (120) for returning the regeneration wastewater of the cation exchanger (5) to the impure salt precipitation tank (1), a membrane filter B wastewater return pipe (120) for returning the wastewater of the membrane filter B (8) to the impure salt precipitation tank (1), and a membrane filter B wastewater return pipe (121) for returning the wastewater of the membrane filter B (8) to the impure salt precipitation tank (1). a calcium sulfate precipitation tank (10) for treating the retained water of the nanofiltration membrane separator (9); a nanofiltration concentrated water return pipe (140) for returning the retained water of the nanofiltration membrane separator (9) to the calcium sulfate precipitation tank (10); a lime milk adding device (280) for adding lime to the retained water of the nanofiltration membrane separator (9); a calcium sulfate precipitation tank produced water return pipe (150) for returning the produced water of the calcium sulfate precipitation tank (10) to the miscellaneous salt precipitation tank (1); and a reverse osmosis device (280) for returning the reverse osmosis device (280) to the reverse osmosis device (280). The invention also includes a reverse osmosis B concentrated water return pipe (160) for returning concentrated water from the separator B (13) to the salt water concentrator (12), a mother liquor return crystallizer pipe (170) for returning part of the crystallization mother liquor to the evaporator, and a mother liquor return mixed salt precipitation tank pipe (180) for returning part of the crystallization mother liquor to the mixed salt precipitation tank (1); and also includes a plurality of sediment filter pressing and drying devices, a plurality of membrane backwashing and chemical cleaning devices, at least one cation exchanger regeneration device, a plurality of lifting pumps and an automatic control device.

[0027] In order to increase the regeneration period of the cation exchanger, a membrane filter A (4) and a membrane filter A wastewater return pipe (110) for returning the wastewater of the membrane filter A (4) to the mixed salt precipitation tank (1) are further provided between the magnesium hydroxide precipitation tank (3) and the cation exchanger (5).

[0028] The membrane filter A (4) is at least one of a cross-flow internal pressure tubular membrane filter and a cross-flow internal pressure capillary membrane filter. The membrane filter B is one of various types of ultrafiltration or microfiltration.

[0029] When the salt content of the raw water is less than 2%, a reverse osmosis separator A (11) is provided between the nanofiltration membrane separator (9) and the salt water concentrator (12). The concentrated water of the reverse osmosis separator A (11) enters the salt water concentrator (12), and the fresh water thereof is recycled water (310).

[0030] When the salt content of the raw water is greater than 2%, it is characterized in that there is a dilution pipeline (190) for adding recycled water (310) between the cation exchanger (5) and the oxidation contactor (6) to adjust the salt content to between 1-2% to facilitate the reaction efficiency of the subsequent biofilm reactor (7).

[0031] The oxidant is ozone, and the oxidant adding device (260) is an ozone generator, an ozone adding facility and an ozone catalytic bed.

[0032] The oxidant is hydrogen peroxide, and the oxidant adding device (260) is a hydrogen peroxide metering adding facility.

[0033] The brine concentrator (12) is at least one of an electrodialysis (ED) device, a steam mechanical recompression evaporator, a multiple-effect evaporator, and a single-effect evaporator.

[0034] The evaporation crystallization device is at least one of a steam mechanical recompression evaporation crystallizer, a multi-effect evaporation crystallizer, and a single-effect crystallization evaporation crystallizer.

[0035] The mother liquor dryer is a spray dryer or an evaporation pond.

[0036] The method for treating wastewater resources using the wastewater resource treatment device comprises the following steps: adding a flocculant to the raw water (300) through a flocculant adding device (210) and a coagulant adding device (220) to generate a small amount of insoluble salts (410) containing phosphate and organic pollutants, and precipitating the insoluble salts (410) in a salt precipitation tank (1), wherein the insoluble salts (410) form solid waste; adding a small amount of soda ash (sodium carbonate) to the water produced by the salt precipitation tank (1) through a soda ash adding device (230), and precipitating the generated calcium carbonate (320) in a calcium carbonate precipitation tank (2), thereby obtaining calcium carbonate (320); adding caustic soda (sodium hydroxide) to the water produced by the calcium carbonate precipitation tank (2) to a pH of 11-12 through a caustic soda adding device (240), and generating calcium carbonate (320). The magnesium hydroxide (330) is precipitated in the magnesium hydroxide precipitation tank (3) to obtain magnesium hydroxide (330); the water produced by the magnesium hydroxide precipitation tank (3) is acidified by an acid adding device (250) to adjust the pH value to 5-8, and enters the cation exchanger (5) for softening; the regenerated wastewater of the cation exchanger (5) is returned to the salt precipitation tank (1) through the cation exchanger regeneration wastewater return pipe (120); the oxidant is added to the water produced by the cation exchanger (5) through the oxidant adding device (260), and enters the oxidation contactor (6), and the biodegradability of organic pollutants is improved through oxidation reaction; the effluent of the oxidation contactor (6) enters the biofilm reactor (7), and the biochemical degradation reaction of organic pollutants occurs, and the water produced by the biofilm reactor (7) is filtered through a membrane The wastewater generated by the filtration of the membrane filter B flows back to the salt precipitation tank (1) through the wastewater return pipe (130) of the membrane filter B; the water produced by the membrane filter B enters the nanofiltration membrane separator (9); the retained water of the nanofiltration membrane separator (9) is added with lime milk through the lime milk adding device (280); the calcium sulfate (340) produced is precipitated in the calcium sulfate precipitation tank (10) to obtain calcium sulfate (340); the water produced by the calcium sulfate precipitation tank (10) flows back to the salt precipitation tank (1) through the calcium sulfate precipitation tank return pipe (150); the water permeated by the nanofiltration membrane separator (9) enters the salt water concentrator (12); the fresh water of the salt water concentrator (12) is treated by the reverse osmosis B (13) to obtain the recycled water (310); the concentrated water of the reverse osmosis B (13) is returned to the salt water concentrator (12) through the reverse osmosis B concentrated water return pipe (150); the concentrated water of the reverse osmosis B (13) is returned to the salt water concentrator (12 ... The concentrated water produced by the salt water concentrator (12) enters the evaporation crystallization device (14), and the steam produced by the evaporation crystallization device (14) is recycled through a heat recovery device to obtain recycled water (310). The evaporation concentration is controlled so that the sodium nitrate in the hot mother liquor in the evaporation crystallization device (14) is close to saturation. The hot mother liquor is separated through a hot separator (15) to obtain sodium chloride (350). The mother liquor separated by the hot separator (15) is cooled to initiate the sodium nitrate crystallization process, and is separated through a cold separator (16) to obtain sodium nitrate (360). Most of the mother liquor separated by the cold separator (16) is refluxed to the evaporation crystallization device (14) through the mother liquor reflux crystallizer pipeline (170) to continue evaporation crystallization, and the cycle is repeated.When organic pollutants and other impurities in the mother liquor affect the purity of sodium chloride (350) and sodium nitrate (360), part of the mother liquor is refluxed to the impurity salt precipitation tank (1) through the mother liquor reflux impurity salt precipitation tank pipeline (180), and most of the pollutants therein are eliminated through the impurity salt precipitation tank (1) and its subsequent processes; in order to further ensure the purity of sodium chloride (350) and sodium nitrate (360), a small part of the mother liquor is dried by the mother liquor dryer (17) to produce a mother liquor drying product (420). ;

[0037] In order to increase the regeneration period of the cation exchanger, a membrane filter A (4) is further provided between the magnesium hydroxide precipitation tank (3) and the acid adding device (250). The water produced by the membrane filter A (4) enters the cation exchanger (5) after acid addition, and the waste water of the membrane filter A (4) flows back to the miscellaneous salt precipitation tank (1) through the waste water return pipe (110) of the membrane filter A.

[0038] When the salt content of the raw water is less than 2%, a reverse osmosis separator A (11) is provided between the nanofiltration membrane separator (9) and the salt water concentrator (12). Fresh water from the reverse osmosis separator A (11) is recycled water (310), and concentrated water from the reverse osmosis separator A (11) enters the salt water concentrator (12).

[0039] When the content of difficult-to-degrade organic pollutants in the raw water is high, the addition of oxidants and the biochemical degradation reaction are repeated at least once.

[0040] When the salt content of the raw water is greater than 2%, recycled water (310) is added between the cation exchanger (5) and the oxidation contactor through the dilution line (190) to adjust the salt content to below 2% to facilitate the reaction efficiency of the subsequent biofilm reactor (7).

Claims

1. A sewage resource zero-discharge treatment device, characterized in that The invention comprises, in sequence, a flocculant adding device (210), a coagulant adding device (220), a salt precipitation tank (1), a soda adding device (230), a calcium carbonate precipitation tank (2), a caustic soda adding device (240), a magnesium hydroxide precipitation tank (3), an acid adding device (250), a cation exchanger (5), an oxidant adding device (260), an oxidation contactor (6), a biofilm reactor (7), a blower (270), a membrane filter B (8), a nanofiltration membrane separator (9), a salt water concentrator (12), an evaporation crystallization device (14), a hot separator (15), a cold separator (16), and a mother liquor dryer (17); and also comprises a cation exchanger regeneration wastewater return pipe (120) for returning the regenerated wastewater of the cation exchanger (5) to the salt precipitation tank (1), a membrane filter B wastewater return pipe (130) for returning the wastewater of the membrane filter B (8) to the salt precipitation tank (1), A calcium sulfate precipitation tank (10) for treating retained water of a nanofiltration membrane separator (9); a nanofiltration concentrated water return pipe (140) for returning the retained water of the nanofiltration membrane separator (9) to the calcium sulfate precipitation tank (10); a lime milk adding device (280) for adding lime to the retained water of the nanofiltration membrane separator (9); a calcium sulfate precipitation tank produced water return pipe (150) for returning produced water of the calcium sulfate precipitation tank (10) to a miscellaneous salt precipitation tank (1); and a reverse osmosis separator (280) for returning produced water of the calcium sulfate precipitation tank (10) to a miscellaneous salt precipitation tank (1). The invention also includes a reverse osmosis B concentrated water return pipe (160) for returning concentrated water B (13) to the brine concentrator (12), a mother liquor return crystallizer pipe (170) for returning part of the crystallization mother liquor to the evaporator, and a mother liquor return mixed salt precipitation tank pipe (180) for returning part of the crystallization mother liquor to the mixed salt precipitation tank (1); and also includes a plurality of sediment filter press drying devices, a plurality of membrane backwashing and chemical cleaning devices, at least one cation exchanger regeneration device, a plurality of lifting pumps and an automatic control device.

2. The wastewater resource zero-discharge treatment device according to claim 1 is characterized in that A membrane filter A (4) and a membrane filter A wastewater return pipe (110) for returning the wastewater of the membrane filter A (4) to the mixed salt precipitation tank (1) are also provided between the magnesium hydroxide precipitation tank (3) and the cation exchanger (5).

3. The wastewater resource zero-discharge treatment device according to claim 1 is characterized in that A reverse osmosis separator A (11) is provided between the nanofiltration membrane separator (9) and the salt water concentrator (12). The concentrated water of the reverse osmosis separator A (11) enters the salt water concentrator (12), and the fresh water thereof is recycled water (310).

4. The wastewater resource zero-discharge treatment device according to claim 1 is characterized in that A dilution pipeline (190) for adding recycled water (310) is also provided between the cation exchanger (5) and the oxidation contactor (6).

5. The wastewater resource zero-discharge treatment device according to claim 1 is characterized in that The brine concentrator (12) is at least one of an electrodialysis (ED) device, a steam mechanical recompression evaporator, a multiple-effect evaporator, and a single-effect evaporator.

6. The wastewater resource zero-discharge treatment device according to claim 1 is characterized in that The evaporation crystallization device (14) is at least one of a steam mechanical recompression evaporation crystallizer, a multi-effect evaporation crystallizer, and a single-effect crystallization evaporation crystallizer.

7. A method for treating wastewater as a resource with zero discharge, characterized in that The wastewater resource recovery zero-discharge treatment device according to claim 1, 4, 5 or 6 comprises the following steps: a flocculant is added to the raw water (300) through a flocculant adding device (210) and a coagulant adding device (220) is added to the coagulant to generate a small amount of insoluble salts (410) containing phosphates and organic pollutants, which are precipitated in a salt precipitation tank (1), and the insoluble salts (410) form solid waste; a soda ash adding device (230) is added with a slightly excessive amount of soda ash (sodium carbonate) to the water produced by the salt precipitation tank (1), and the generated calcium carbonate (320) is precipitated in a calcium carbonate precipitation tank (2) to obtain calcium carbonate (320); a caustic soda adding device (240) is added with caustic soda (sodium hydroxide) to a pH of 11-12 to generate magnesium hydroxide (330) to the magnesium hydroxide precipitation tank (3). The magnesium hydroxide (330) is obtained by precipitating the magnesium hydroxide precipitation tank (3) with an acid addition device (250) to adjust the pH value to 5-8, and then the water is fed into the cation exchanger (5) for softening. The regenerated wastewater of the cation exchanger (5) is fed back into the miscellaneous salt precipitation tank (1) through the cation exchanger regeneration wastewater return pipe (120); the oxidant is added to the water produced by the cation exchanger (5) through the oxidant addition device (260), and then the water is fed into the oxidation contactor (6), and the biodegradability of the organic pollutants is improved through the oxidation reaction; the effluent of the oxidation contactor (6) enters the biofilm reactor (7), and the biochemical degradation reaction of the organic pollutants occurs. The water produced by the biofilm reactor (7) is filtered through the membrane filter B, and the wastewater generated by the filtration of the membrane filter B is fed back into the miscellaneous salt precipitation tank (1) through the membrane filter B wastewater return pipe (130); The water produced by the membrane filter B enters the nanofiltration membrane separator (9), the retained water of the nanofiltration membrane separator (9) is added with lime milk through the lime milk adding device (280), the generated calcium sulfate (340) is precipitated in the calcium sulfate precipitation tank (10) to obtain calcium sulfate (340), the water produced by the calcium sulfate precipitation tank (10) is returned to the miscellaneous salt precipitation tank (1) through the calcium sulfate precipitation tank return pipe (150), the water permeated by the nanofiltration membrane separator (9) enters the salt water concentrator (12); the fresh water of the salt water concentrator (12) is treated by the reverse osmosis B (13) to obtain the recycled water (310), the concentrated water of the reverse osmosis B (13) is returned to the salt water concentrator (12) through the reverse osmosis B concentrated water return pipe (160); the concentrated water produced by the salt water concentrator (12) enters the evaporation crystallization device (14), the steam produced by the evaporation crystallization device (14) is passed through the heat recovery device to obtain the recycled water (310), and the evaporation concentration is controlled so that the sodium nitrate is concentrated in the evaporation crystallization device. The hot mother liquor in the reactor (14) is nearly saturated, and the hot mother liquor is separated by a hot separator (15) to obtain sodium chloride (350). The mother liquor separated by the hot separator (15) is cooled to initiate a sodium nitrate crystallization process, and is separated by a cold separator (16) to obtain sodium nitrate (360). Most of the mother liquor separated by the cold separator (16) is refluxed to the evaporation crystallization device (14) through a mother liquor reflux crystallizer pipeline (170) to continue evaporation crystallization, and the cycle is repeated. When organic pollutants and other impurities in the mother liquor affect the purity of sodium chloride (350) and sodium nitrate (360), part of the mother liquor is refluxed to the miscellaneous salt precipitation tank (1) through a mother liquor reflux miscellaneous salt precipitation tank pipeline (180), and most of the pollutants therein are eliminated by the miscellaneous salt precipitation tank (1) and its subsequent processes. In order to further ensure the purity of sodium chloride (350) and sodium nitrate (360), a small part of the mother liquor is dried by a mother liquor dryer (17) to produce a mother liquor dried product (420).

8. The method for treating wastewater as a resource with zero discharge according to claim 7, characterized in that A membrane filter A (4) is also provided between the magnesium hydroxide precipitation tank (3) and the acid adding device (250). The water produced by the membrane filter A (4) enters the cation exchanger (5) after acid addition, and the waste water of the membrane filter A (4) is returned to the miscellaneous salt precipitation tank (1) through the waste water return pipe (110) of the membrane filter A.

9. The method for treating wastewater as a resource with zero discharge according to claim 7, characterized in that A reverse osmosis separator A (11) is provided between the nanofiltration membrane separator (9) and the salt water concentrator (12). Fresh water from the reverse osmosis separator A (11) is recycled water (310), and concentrated water from the reverse osmosis separator A (11) enters the salt water concentrator (12).

10. The method for treating wastewater as a resource with zero discharge according to claim 7, 8 or 9, characterized in that The addition of the oxidant and the biochemical degradation reaction are repeated at least once.

11. The method for treating wastewater as a resource with zero discharge according to claim 7, 8, 9 or 10, characterized in that Recycled water (310) is added between the cation exchanger (5) and the oxidation contactor through a dilution line (190) to adjust the salt content to less than 2%.

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