Zero-emission treatment process and system for low-carbon black liquor from Nifis

Abstract

The invention belongs to the technical field of pulping wastewater treatment, and relates to a zero-discharge treatment process and system for a low-carbon pulping black liquor of Nafius, and the treatment process comprises the following steps: (1) chemical treatment; (2) impurity treatment; (3) oxidizing and decolorizing; (4) performing ultrafiltration treatment, nanofiltration treatment, ED concentration treatment, MVR evaporation concentration treatment and solid-liquid separation; (5) ion membrane electrolysis treatment; and (6) treating sludge and sludge residues. According to the invention, a treatment process combining chemical treatment as a main process and physical treatment as an auxiliary process is adopted, and the treated material is completely recycled to realize complete zero emission; the occupied area is small and is 1 / 5 of that of a traditional process; inorganic solids can be decomposed and synthesized again through an electrolysis system, so that complete utilization is realized; and full-automatic operation can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of pulping wastewater treatment and relates to a Nafis low-carbon pulping black liquor zero-discharge treatment process and system. Background Art

[0002] The "Nafis Eco-Pulping" technology is an innovative low-carbon ecological pulping method from the UK. It uses agricultural straw or annual grass plants (such as reeds, etc.) as raw materials to extract straw plant cellulose, which can be directly used to make a variety of paper products from high-strength corrugated paper to household paper, as well as paper molded packaging, industrial packaging and other products. This process technology completely breaks through the bottleneck of high energy consumption and high cost of traditional straw pulping technology, and has the characteristics of being completely sulfur-free, low energy consumption, low water consumption, high fiber yield, low investment cost, and environmentally friendly.

[0003] The pulping black liquor produced by the "Nafis Ecological Pulping" technology is a pulping wastewater with high COD, high temperature, and high SS, which is difficult to treat. The pulping liquid contains a large amount of additives. At present, most of these pulping wastewater treatments use biochemical methods. In order to adapt to the treatment capacity of the biochemical method, the pulping wastewater needs to be diluted by about 10 times, which not only increases the treatment workload, but also increases the amount of solid wastes that are flotated and precipitated. The floor space and energy consumption of the treatment process are greatly increased, and the wastewater treatment instead forms a large amount of hazardous waste; the treated water is discharged into the basin and the sea, causing serious pollution to the environment. With the current pulping technology, the water consumption is 15-20 tons of water / ton of pulp, which consumes a large amount of water resources and causes huge pollution to the environment; and the residual additives in the pulping wastewater cannot be precipitated and removed by biochemical methods. Therefore, an effective Nafis low-carbon pulping black liquor treatment process is needed. Summary of the invention

[0004] In view of the deficiencies of the above-mentioned prior art, the present invention provides a Nafis low-carbon pulping black liquor zero-discharge treatment process and system, and the specific technical scheme is as follows:

[0005] The first object of the present invention is to provide a Nafis low-carbon pulping black liquor zero-discharge treatment process, comprising the following steps:

[0006] (1) chemically treating the collected and stored pulping black liquor, and then separating the solid and liquid to obtain sludge and clear liquid;

[0007] (2) further treating the impurities in the clear liquid after solid-liquid separation to obtain sludge and clean water;

[0008] (3) The clean water produced after impurity treatment enters oxidation decolorization treatment;

[0009] (4) The water subjected to the oxidation decolorization treatment is subjected to ultrafiltration treatment, nanofiltration treatment, ED concentration treatment, MVR evaporation concentration treatment, and then solid-liquid separation is performed to obtain sodium chloride solid and centrifugal mother liquor;

[0010] (5) solid sodium chloride is treated by ion membrane electrolysis to obtain alkali solution, hydrochloric acid and sodium hypochlorite solution, and the sodium hypochlorite enters step (3) for oxidative decolorization;

[0011] (6) The sludge produced in step (1), the sludge produced in step (2) and the small amount of evaporation mother liquor produced in step (4) are collected, precipitated, concentrated and dehydrated to obtain a filtrate and a sludge cake, and the filtrate is returned to the original water tank for re-treatment.

[0012] The Nafis low-carbon pulping black liquor zero-emission treatment process of the present invention adopts a treatment process that combines chemical treatment as the main method and physical treatment as the auxiliary method. The treated materials are completely recycled and reused to achieve complete zero emission; the inorganic solids can be decomposed and synthesized through the electrolysis system to achieve complete utilization.

[0013] Furthermore, the chemical treatment in step (1) is to add the catalyst, the flocculation agent and the acid solution in sequence for reaction treatment; the reaction time for adding the catalyst is 40-110 minutes, and the reaction time for adding the flocculation agent is 50-90 minutes; and the pH is adjusted to 4-6.

[0014] Furthermore, the catalyst is a mixture of cellulase, polysaccharide and small molecule amino acid in a mass ratio of 6:3:1, and the added amount of the catalyst is 2-6‰ of the mass of pulping black liquor.

[0015] The catalyst is used to accelerate and promote the degradation reaction of lignin in pulping black liquor and the removal of residual additives, so that the pulping black liquor is easier to separate liquid from solid.

[0016] Furthermore, the flocculating agent is an anionic composite flocculating agent prepared by mixing ethyl cellulose water dispersion (type b) (abbreviated as EHEC-B) and anionic polyacrylamide in a mass ratio of 1:20, stirring at 50° C. for 20-30 minutes, and the dosage in water is 3-15 ppm.

[0017] Since the pulping black liquor contains positively charged pollutants, such as pigments, fillers, etc., the anionic composite flocculant used in the present invention can combine with these pollutants through charge neutralization to form larger floccules, thereby effectively removing suspended matter and organic matter in the wastewater.

[0018] The anionic composite flocculant of the present invention contains hydroxyethyl and hydroxypropyl substituents in its chemical structure, has good solubility and dispersibility, and can quickly form a uniform and stable dispersion system; has excellent thickening effect, can effectively improve the viscosity and rheological properties of the liquid; has good gelling properties, and can form a firm and flexible gel structure under appropriate conditions; has good stability and corrosion resistance, can still maintain high stability in acidic and alkaline environments, and also has good antioxidant properties to oxidants and reducing agents; also has high thermal stability, and can still maintain good dispersion and thickening effects at higher temperatures.

[0019] Furthermore, the acid solution is sulfuric acid or hydrochloric acid.

[0020] The second object of the present invention is to provide a system for the above-mentioned Nafis low-carbon pulping black liquor zero-discharge treatment process, comprising a raw water tank, an air flotation flocculation sedimentation system, a pretreatment system, an oxidation decolorization system, an ultrafiltration system, a nanofiltration / reverse osmosis system, an ED concentration system and an MVR evaporation system connected in sequence; a dosing system is connected to the air flotation flocculation sedimentation system;

[0021] The water outlets of the nanofiltration / reverse osmosis system, ED concentration system and MVR evaporation system are connected to the reuse water pool; the sludge discharge outlet of the flotation flocculation sedimentation system, the sludge discharge outlet of the pretreatment system and the mother liquor discharge outlet of the MVR evaporation system are connected to the sludge filter press system; the filtrate outlet of the sludge filter press system is connected to the raw water pool; the ion membrane electrolysis system is connected to the oxidation decolorization system.

[0022] The system provided by the present invention for the zero-emission treatment process of the above-mentioned Nafis low-carbon pulping black liquor comprises the following steps: the raw water pool is used to collect the produced pulping black liquor, and the water quality can be adjusted by mixing in the raw water pool; the air flotation flocculation precipitation system is used for comprehensive chemical treatment, and can achieve 80%-90% solid-liquid separation; the dosing system is used to add catalysts, flocculation reagents and acid solution to the air flotation flocculation precipitation system; the pretreatment system removes 95% of impurities such as suspended matter, colloids, organic matter (microorganisms) and the like of some larger particles in the water; the oxidative decolorization system is used for oxidative decolorization of the clean water produced after the impurity treatment of the pretreatment system; under the very strong oxidizing property of hypochlorous acid, hypochlorous acid and small molecular organic matter in the water react quickly to generate carbon dioxide and water, greatly reducing COD and SS in the water, so that the water quality index meets the water inlet requirements of the ultrafiltration system, and the hypochlorous acid dosage is 20 -100ppm; after being treated by the ultrafiltration system, bacteria, colloids, suspended solids, rust, macromolecular organic matter, etc. in the water are effectively removed; the water produced by the ultrafiltration system is pressurized by a high-pressure pump and then enters the nanofiltration / reverse osmosis system for concentration and desalination treatment, selectively removing macromolecules, organic matter, heavy ions and some charged ions in the aqueous solution; the concentrated water produced by the nanofiltration / reverse osmosis system enters the ED concentration system for further concentration; the water produced by the nanofiltration / reverse osmosis system and the ED concentration system meets the requirements and enters the reuse water pool; the concentrated liquid of the ED concentration system enters the MVR evaporation system for concentration treatment, and part of the salt produced after evaporation in the MVR evaporation system is evaporated by the ion membrane electrolysis system to produce alkali solution, hydrochloric acid and sodium hypochlorite solution, among which the alkali solution and hydrochloric acid enter the production process, and the sodium hypochlorite enters the oxidation decolorization system. The remaining salt can be exported, and the steam condensate produced enters the reuse water pool for reuse. The sludge produced by the flotation flocculation sedimentation system, the mud residue separated by the pretreatment system, and the small amount of evaporation mother liquor of the MVR evaporation system are collected, precipitated, concentrated, dehydrated and processed by the sludge filter press system. The filtrate is returned to the original water pool for re-treatment, and the mud cake (containing a large amount of organic matter) is incinerated or exported as lignin.

[0023] Furthermore, the pretreatment system, the ultrafiltration system and the nanofiltration / reverse osmosis system are provided with pipelines for returning to the flotation flocculation sedimentation system; and the ED concentration system is provided with a fresh water return pipeline for returning to the nanofiltration / reverse osmosis system.

[0024] The ultrafiltration recovery rate of the ultrafiltration system is about 95%, that is, the water production ratio is 95%, and most of the remaining 5% of the concentrated liquid is returned to the flotation flocculation sedimentation system for circulation treatment; the concentrated water of the nanofiltration / reverse osmosis system is circulated for treatment. Since the salt content of the fresh water in the ED concentration system is still relatively high, it needs to re-enter the nanofiltration / reverse osmosis system for desalination treatment.

[0025] Furthermore, the flotation flocculation sedimentation system includes an integrated flotation flocculation sedimentation machine; the pretreatment system includes a bag filter and a solid-liquid separation filter.

[0026] The flotation flocculation sedimentation machine is a highly efficient sewage treatment equipment that combines the three technologies of flotation, flocculation and sedimentation to remove suspended matter, grease and other impurities in water. The bag filter of the pretreatment system can remove some larger particles of suspended matter, colloids, organic matter (microorganisms), etc. in the water, with a filtration accuracy of about 100 microns. The effluent enters the solid-liquid separation filter through a booster pump. The solid-liquid separation filter contains a special filter element that can retain particulate matter larger than 0.2 microns. After further filtration, the separated impurities gather on the surface of the filter element to form a filter cake layer. The filter cake falls off after backblowing and is discharged into the sludge concentration tank through the residue discharge port.

[0027] Furthermore, the ultrafiltration system comprises a security filter and an ultrafiltration membrane assembly, wherein the ultrafiltration membrane assembly is a hollow fiber ultrafiltration membrane assembly; and the reverse osmosis nanofiltration membrane in the nanofiltration / reverse osmosis system is an alkali-resistant nanofiltration membrane.

[0028] When entering the ultrafiltration membrane assembly of the ultrafiltration system, it first passes through the security filter to remove the trace impurities, colloids and microorganisms remaining in the previous treatment unit to ensure the quality of the water entering the ultrafiltration membrane assembly. After entering the ultrafiltration membrane assembly, under low pressure, some small molecular solutes such as inorganic salt ions and water molecules can pass through the ultrafiltration membrane, while macromolecular substances exceeding a certain molecular weight are intercepted into concentrated liquid, which can effectively remove particles, colloids, bacteria, heat sources and organic matter in the water. The hollow fiber ultrafiltration membrane assembly adopts advanced external pressure membrane separation technology and performs separation at room temperature and low pressure. It has the advantages of low energy consumption, high filtration accuracy, large water production and strong anti-fouling ability. It can effectively filter out harmful substances such as bacteria, colloids, suspended matter, rust, macromolecular organic matter in the water. Alkali-resistant nanofiltration membrane allows solvent molecules or certain low molecular weight solutes or low-valent ions to pass through. The surface separation layer is composed of polyelectrolytes and has a certain retention rate for inorganic salts. Alkali-resistant nanofiltration membrane has good film-forming properties, thermal stability, chemical stability, acid and alkali resistance and microbial corrosion resistance, chlorine resistance, as well as high water flux and high salt retention rate, and resistance to colloid and suspended matter pollution.

[0029] Furthermore, the MVR evaporation system includes an MVR evaporator and a centrifuge.

[0030] The MVR evaporator performs evaporation, concentration and crystallization. The slurry with a certain solid-liquid ratio after supersaturated crystallization in the cooling crystallizer with a certain concentration enters the centrifuge for solid-liquid separation to obtain the solid product of sodium chloride. The centrifuged mother liquor can enter the mother liquor tank and be transported back to the evaporator by the raw material pump. The evaporated mother liquor is quantitatively discharged to the sludge filter press system.

[0031] Furthermore, the sludge filter press system includes a sludge concentration tank and a plate and frame filter press device.

[0032] The sludge generated by the flotation flocculation sedimentation system and the sludge separated by the pretreatment system first enter the sludge thickening tank of the sludge filter press system. The sludge thickening tank precipitates, concentrates and stabilizes the sludge, and is also an important facility for sludge treatment and storage. The sludge in the sludge thickening tank is mixed and pumped to the plate and frame filter press for dehydration treatment.

[0033] The beneficial effects of the present invention are:

[0034] The Nafes low-carbon pulping black liquor zero-emission treatment process and system provided by the present invention adopts a treatment process that combines chemical treatment as the main method and physical treatment as the auxiliary method; the treated materials are completely recycled and reused to achieve complete zero emissions; the land occupation is small, which is 1 / 5 of the traditional process; the inorganic solids can be decomposed and synthesized through the electrolysis system to achieve complete utilization; and fully automated operation can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the zero-emission treatment process of Nafis low-carbon pulping black liquor of the present invention.

[0036] Description of the markings in the figure:

[0037] 1. Raw water pool; 2. Air flotation flocculation sedimentation system; 3. Pretreatment system; 4. Oxidation decolorization system; 5. Ultrafiltration system; 6. Nanofiltration / reverse osmosis system; 7. ED concentration system; 8. MVR evaporation system; 9. Recycled water pool; 10. Sludge filter press system; 11. Ion membrane electrolysis system; 12. Dosing system. DETAILED DESCRIPTION

[0038] The principles and features of the present invention are described below in conjunction with embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0039] Example:

[0040] Taking the treatment of pulping black liquor in Linqing Nafis Paper Mill as an example, the CODcr of the pulping black liquor is about 25000 mg / L, the SS is about 28000 mg / L, and the pH is about 10.

[0041] like Figure 1 As shown in the figure, a zero-emission treatment process of low-carbon pulping black liquor of Nafis:

[0042] (1) The produced pulping black liquor is pumped to the raw water pool 1 for collection, and the water quality is adjusted by mixing;

[0043] (2) Then enter the air flotation flocculation sedimentation system 2, and the dosing system 12 adds a chemical catalyst, a flocculation reaction agent and an acid solution to the air flotation flocculation sedimentation system 2 in sequence, and through comprehensive chemical treatment, 80%-90% solid-liquid separation can be achieved; wherein the catalyst is a mixture of cellulase, polysaccharide and small molecule amino acid in a mass ratio of 6:3:1, and the addition amount of the catalyst is 4‰ of the mass of pulping black liquor, and the catalyst is added for 100 minutes; the flocculation reaction agent is an anionic composite flocculation reaction agent prepared by stirring ethyl cellulose water dispersion (type b) (abbreviated as EHEC-B) and anionic polyacrylamide at a mass ratio of 1:20 at 50°C for 30 minutes, and the water body addition amount is 10ppm, and the flocculation reaction agent is added for 60 minutes; the acid solution is sulfuric acid, and the pH is adjusted to about 5;

[0044] (3) The clear liquid produced by the flotation flocculation sedimentation system 2 is pumped into the pretreatment system 3. The bag filter can remove some larger particles of suspended solids, colloids, organic matter (microorganisms), etc. in the water. The filtration accuracy is about 100 microns. The effluent passes through the booster pump and enters the solid-liquid separation filter. The solid-liquid separation filter contains a special filter element that can retain particulate matter larger than 0.2 microns. After further filtration, the separated impurities gather on the surface of the filter element to form a filter cake layer. After backblowing, the filter cake falls off and is discharged into the sludge concentration tank through the residue discharge port. After passing through the pretreatment system 3, 95% of the impurities in the water have been removed;

[0045] (4) The purified water produced by the pretreatment system 3 enters the oxidation decolorization system 4 for oxidation decolorization treatment. Under the very strong oxidizing property of hypochlorous acid, hypochlorous acid and small molecular organic matter in the water quickly react to generate carbon dioxide and water, greatly reducing the COD and SS in the water, so that the water quality index meets the water inlet requirements of the ultrafiltration system 5. The hypochlorous acid dosage is 50ppm; after oxidation decolorization treatment, the COD of the produced water is less than 1500mg / L; SS is less than 10mg / L, TDS≈20000mg / L; turbidity is less than 5NTU;

[0046] (5) The water treated by the oxidation decolorization system 4 first enters the security filter of the ultrafiltration system 5 to remove the trace impurities, colloids and microorganisms remaining in the previous treatment unit to ensure the quality of the water entering the ultrafiltration membrane assembly. Then, it enters the ultrafiltration membrane assembly. Under low pressure, some small molecular solutes such as inorganic salt ions and water molecules can pass through the ultrafiltration membrane, while macromolecular substances exceeding a certain molecular weight are intercepted and formed into concentrated liquid, which can effectively remove harmful substances such as bacteria, colloids, suspended matter, rust, macromolecular organic matter in the water, and significantly reduce COD, SS, SDI and turbidity. The ultrafiltration recovery rate of the ultrafiltration system 5 is about 95%, that is, the water production ratio is 95%, and most of the other 5% of the concentrated liquid is refluxed to the air flotation flocculation sedimentation system 2 for circulation treatment;

[0047] (6) The water produced by the ultrafiltration system 5 is pressurized by a high-pressure pump and then enters the nanofiltration / reverse osmosis system 6 for concentration and desalination treatment, selectively removing macromolecules, organic matter, heavy ions and some charged ions in the aqueous solution; the concentrated water produced by the nanofiltration / reverse osmosis system 6 enters the ED concentration system 7 for further concentration; the concentrated water of the nanofiltration / reverse osmosis system 6 is circulated for treatment; the water produced by the nanofiltration / reverse osmosis system 6 and the ED concentration system 7 meets the requirements and enters the reuse water pool 9; the fresh water of the ED concentration system 7 still has a relatively high salt content and needs to re-enter the nanofiltration / reverse osmosis system 6 for desalination treatment;

[0048] (7) The concentrated liquid of the ED concentration system 7 enters the MVR evaporator of the MVR evaporation system 8 for evaporation, concentration and crystallization. The slurry with a certain solid-liquid ratio after supersaturated crystallization in the cooling crystallizer containing a certain concentration of feed liquid enters the centrifuge for solid-liquid separation to obtain a solid product of sodium chloride. The centrifuged mother liquor can enter the mother liquor tank and be transported back to the evaporator by the raw material pump. The evaporated mother liquor is quantitatively discharged to the sludge concentration tank of the sludge filter press system 10;

[0049] (8) After evaporation in the MVR evaporation system 8, part of the salt produced is passed through the ion membrane electrolysis system 11 to produce alkali solution, hydrochloric acid and sodium hypochlorite solution, of which the alkali solution and hydrochloric acid enter the production process, and the sodium hypochlorite enters the oxidation decolorization system 4. The remaining salt can be exported, and the steam condensate produced enters the reuse water pool 9 for reuse;

[0050] (9) The sludge produced by the flotation flocculation sedimentation system 2, the sludge separated by the pretreatment system 3, and a small amount of evaporation mother liquor produced by the MVR evaporation system 8 first enter the sludge concentration tank of the sludge filter press system 10. The sludge concentration tank precipitates, concentrates, and stabilizes the sludge, and is also an important facility for sludge treatment and storage. The sludge in the sludge concentration tank is mixed and pumped to a plate and frame filter press for dehydration. The filtrate is returned to the original water tank 1 for re-treatment, and the mud cake (containing a large amount of organic matter) is incinerated or exported as lignin.

[0051] The present invention adopts a treatment process that combines chemical treatment as the main method and physical treatment as the auxiliary method, which can achieve the following goals: 1) Complete reuse of produced water; 2) Water content of solid waste is less than 70% (recyclable); 3) COD of produced water is less than 500ppm. 4) The system occupies a small area, which is 1 / 5 of the traditional process; 5) Inorganic solids can be decomposed and synthesized through the electrolysis system to achieve full utilization; 5) Fully automated operation can be achieved.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A Nafis low-carbon pulping black liquor zero-discharge treatment process, characterized in that: The steps include: (1) chemically treating the collected and stored pulping black liquor, and then separating the solid and liquid to obtain sludge and clear liquid; (2) further treating the impurities in the clear liquid after solid-liquid separation to obtain sludge and clean water; (3) The clean water produced after impurity treatment enters oxidation decolorization treatment; (4) The water subjected to the oxidation decolorization treatment is subjected to ultrafiltration treatment, nanofiltration treatment, ED concentration treatment, MVR evaporation concentration treatment, and then solid-liquid separation is performed to obtain sodium chloride solid and centrifugal mother liquor; (5) The sodium chloride solid is treated by an ion membrane electrolysis system to obtain an alkali solution, hydrochloric acid and a sodium hypochlorite solution, and the sodium hypochlorite enters step (3) for oxidative decolorization treatment; (6) The sludge produced in step (1), the sludge produced in step (2) and the small amount of evaporation mother liquor produced in step (4) are collected, precipitated, concentrated and dehydrated to obtain a filtrate and a sludge cake, and the filtrate is returned to the original water tank for re-treatment.

2. The zero-discharge treatment process of low-carbon pulping black liquor of Nafis according to claim 1 is characterized in that: The chemical treatment in step (1) is to add the catalyst, the flocculation agent and the acid solution in sequence for reaction treatment; the reaction time for adding the catalyst is 40-110 minutes, and the reaction time for adding the flocculation agent is 50-90 minutes; and the pH is adjusted to 4-6.

3. The zero-discharge treatment process of low-carbon pulping black liquor of Nafis according to claim 2 is characterized in that: The catalyst is prepared by mixing cellulase, polysaccharide and small molecule amino acid in a mass ratio of 6:3:1, and the added amount of the catalyst is 2-6‰ of the mass of pulping black liquor.

4. The zero-discharge treatment process of low-carbon pulping black liquor of Nafis according to claim 2 is characterized in that: The flocculation reaction agent is an anionic composite flocculation reaction agent prepared by mixing ethyl cellulose water dispersion and anionic polyacrylamide at a mass ratio of 1:20 at 50° C. and stirring for 20-30 minutes. The dosage in water is 3-15 ppm.

5. A system for the zero-discharge treatment process of Nafis low-carbon pulping black liquor according to any one of claims 1 to 4, characterized in that: It includes a raw water pool, an air flotation flocculation sedimentation system, a pretreatment system, an oxidation decolorization system, an ultrafiltration system, a nanofiltration / reverse osmosis system, an ED concentration system and an MVR evaporation system connected in sequence; the dosing system is connected to the air flotation flocculation sedimentation system; The water outlets of the nanofiltration / reverse osmosis system, ED concentration system and MVR evaporation system are connected to the reuse water pool; the sludge discharge outlet of the flotation flocculation sedimentation system, the sludge discharge outlet of the pretreatment system and the mother liquor discharge outlet of the MVR evaporation system are connected to the sludge filter press system; the filtrate outlet of the sludge filter press system is connected to the raw water pool; the ion membrane electrolysis system is connected to the oxidation decolorization system.

6. The system according to claim 5, characterized in that The pretreatment system, the ultrafiltration system and the nanofiltration / reverse osmosis system are provided with pipelines that flow back to the air flotation flocculation sedimentation system; the ED concentration system is provided with a fresh water return pipeline that flows back to the nanofiltration / reverse osmosis system.

7. The system according to claim 5, characterized in that The flotation flocculation sedimentation system comprises an integrated flotation flocculation sedimentation machine; the pretreatment system comprises a bag filter and a solid-liquid separation filter.

8. The system according to claim 5, characterized in that The ultrafiltration system comprises a security filter and an ultrafiltration membrane assembly, wherein the ultrafiltration membrane assembly is a hollow fiber ultrafiltration membrane assembly; and the reverse osmosis nanofiltration membrane in the nanofiltration / reverse osmosis system is an alkali-resistant nanofiltration membrane.

9. The system according to claim 5, characterized in that The MVR evaporation system includes an MVR evaporator and a centrifuge.

10. The system according to claim 5, characterized in that The sludge filter pressing system comprises a sludge concentration tank and a plate and frame filter pressing device.

Images