Method and system for separating and recovering salt and sugar in preserved fruit pickling wastewater

Abstract

The invention provides a method and system for separating and recovering salt and sugar in preserved fruit pickling wastewater, and the method mainly comprises the following steps: pretreating the preserved fruit pickling wastewater, preliminarily separating the salt and sugar in the preserved fruit pickling wastewater, and completing the separation of the salt and sugar in the preserved fruit pickling wastewater, concentrating sugar-containing fresh water, and the like, so that the salt and the sugar in the preserved fruit pickling wastewater are separated and recovered. Meanwhile, the invention provides a system for implementing the method. The system comprises wastewater storage equipment, fresh water supply equipment, a pretreatment unit, an electrodialysis unit system, a reverse osmosis membrane concentration system and the like. According to the system, the devices are integrated, so that the recovery and utilization efficiency of sugar and salt in preserved fruit pickling wastewater is greatly improved.

Description

Technical Field

[0001] The present application relates to the field of wastewater treatment, and in particular to a method and system for separating and recovering salt and sugar from preserved fruit pickling wastewater. Background Art

[0002] Wastewater treatment is of great significance to the sustainable development of modern society. However, in the existing technology, it is difficult to treat wastewater containing both salt and sugar. This type of wastewater containing both salt and sugar mainly comes from the pickling of preserved fruits. Preserved fruits refer to products made by pickling various fresh fruits, boiling and dipping in sugar (honey), and drying. They are candied fruit products with characteristics of southern my country. Preserved fruits in my country began in the Tang and Song dynasties, and have been around for more than a thousand years. South China has unique geography and climate, and rich fruit and vegetable resources. Preserved fruit processing has become an important means to solve the problem of fruit and vegetable production and marketing and develop the township economy.

[0003] my country is a major producer of preserved fruits, and the preserved fruit industry has brought considerable economic benefits to the people. However, the preserved fruit processing produces a large amount of wastewater with high salinity and high chemical oxygen demand (COD), which is difficult to treat. Some preserved fruit factories even discharge the wastewater generated during the processing into rivers without treatment or treatment that does not meet the standards, resulting in river water pollution and land salinization year by year. Therefore, the treatment of preserved fruit wastewater is an important factor affecting the development of the preserved fruit industry.

[0004] Preserved fruit wastewater mainly comes from the washing, pickling and other process water loss of preserved fruits, workshop and container cleaning water, etc. Among them, since the concentration of pollutants such as salt and sugar is low, the washing and flushing wastewater can usually be discharged in compliance with the standards through conventional water treatment technology, and the treated wastewater meets the requirements for inclusion in the sewage network. The salt- and sugar-rich pickling wastewater generated in the processing procedures of preserved fruits such as salt pickling and sugar pickling is the most polluted wastewater in the preserved fruit industry because it contains extremely high salt and sugar. The wastewater has high concentration, high salt content, high organic matter content, and very poor biodegradability (heavy salt causes microorganisms to lose activity).

[0005] In the prior art, in addition to using conventional pretreatment to treat the wastewater, the main treatment unit used is to use advanced oxidation to remove COD, or to dilute it with fresh water first, and then use biochemical + advanced oxidation for treatment. However, the above method is sensitive to load shock, has poor operating stability, and the equipment has poor long-term continuous operation integrity, and the equipment occupies a large area. In addition, advanced oxidation also has problems such as high chloride ion interference oxidation and high operating costs. The fresh water dilution method also violates the basic principle that wastewater treatment must not be diluted. In addition, this method mainly treats sugars (reflected as COD values ​​in wastewater treatment), and does not simultaneously treat salts in pickling wastewater, so the pollution of salts in pickling wastewater has not been properly solved. At the same time, because the methods used in the prior art have high use and maintenance costs, some companies even engage in "stealing" in order to save costs.

[0006] The prior art discloses a method for treating preserved fruit wastewater based on membrane integration technology, which uses coagulation and sedimentation, biochemical, advanced oxidation, reverse osmosis membrane separation and ultraviolet disinfection to obtain desalinated water for reuse.

[0007] The prior art discloses a salt-tolerant and efficient COD-degrading bacterium and a composite bacterial agent thereof, a preparation method and an application thereof.

[0008] The prior art discloses a device for treating wastewater from the production of preserved fruits, which combines pretreatment, electro-Fenton advanced oxidation, electro-adsorption desalination and biochemical treatment processes, and the electro-adsorption desalination tank adopts an electro-adsorption integrator.

[0009] It can be seen that the current research direction of the existing technology on preserved fruit pickled wastewater is mainly to remove COD by combining salt-tolerant bacteria, biochemical and advanced oxidation, and to desalinate wastewater by membrane or electrosorption. It mainly removes sugar in wastewater in the form of organic matter, and cannot solve the problem of concentrated water containing high concentrations of COD and salt.

[0010] In fact, salt and sugar are themselves a kind of usable resources, but in the existing treatment of preserved fruit pickled wastewater, they are treated or discharged as "pollutants", which not only pollutes the environment, but also causes waste of resources.

[0011] Therefore, in view of the deficiencies in the prior art, it is urgent for the wastewater treatment field to develop a method and system that can simultaneously separate and recycle sugar and sodium chloride in wastewater. Summary of the invention

[0012] The present application embodiment provides a method for separating and recovering salt and sugar in preserved fruit pickling wastewater, comprising the following steps:

[0013] S1, pretreatment of preserved fruit wastewater: adjust the pH of preserved fruit wastewater to make the pH value of preserved fruit wastewater ≥4, precipitate and clarify the preserved fruit wastewater, filter it, make the suspended matter in the preserved fruit wastewater meet <1mg / L, so as to meet the requirements of electrodialysis water inlet.

[0014] S2, preliminary separation of salt and sugar in the wastewater of pickled fruits: the pretreated wastewater of pickled fruits is passed into the material circulation water tank in the electrodialysis unit system, and the initial water is injected into the concentrated water circulation water tank in the electrodialysis unit system, wherein the initial water is fresh water, wherein the wastewater of pickled fruits passes through the material circulation water tank and sequentially passes through the material circulation pump, the material safety filter and the material heat exchanger to enter the desalination chamber in the electrodialysis unit structure, and the initial water passes through the concentrated water circulation water tank and sequentially passes through the concentrated water circulation pump, the concentrated water safety filter and the concentrated water heat exchanger to enter the concentrating chamber in the electrodialysis unit structure, so that the positive and negative ions in the wastewater of pickled fruits are respectively passed through the anion membrane and the cation membrane in the electrodialysis unit structure to enter the concentrating chamber in the electrodialysis unit structure to obtain salt water, while the sugar in the wastewater of pickled fruits continues to stay in the desalination chamber in the electrodialysis unit structure to obtain sugar-containing fresh water.

[0015] S3, complete the separation of salt and sugar in the wastewater of pickled fruits: the sugar-containing fresh water obtained in S2 is returned to the material circulation water tank, and the salt water flows into the concentrated water circulation water tank, and the sugar-containing fresh water and the salt water are circulated in the electrodialysis unit structure through the material circulation pump and the concentrated water circulation pump respectively, so that the positive and negative ions in the sugar-containing fresh water continuously enter the concentration chamber, until it is detected that the salt content of the sugar-containing fresh water in the material circulation water tank is reduced to the first target concentration, and the salt content of the salt water in the concentrated water circulation water tank is increased to the second target concentration, so as to complete the separation of salt and sugar in the wastewater of pickled fruits.

[0016] S4, concentrating sugar-containing fresh water: the sugar-containing fresh water with salt content reduced to the first target concentration obtained in S3 is discharged from the material circulation water tank through the fresh water discharge pump to the reverse osmosis water inlet tank in the reverse osmosis membrane concentration system, and is concentrated through the membrane concentration unit to obtain sugar-free desalinated water and sugar-containing concentrate, thereby achieving the concentration of sugar-containing fresh water.

[0017] In one embodiment, the following steps are also included:

[0018] The salt water obtained in S3 with the salt content increased to the second target concentration is introduced into the concentrated salt water preparation system through the concentrated water discharge pump, the salt content in the salt water is adjusted, and then introduced into the preserved fruit pickling pool to pickle preserved fruits, or used for other purposes after being adjusted.

[0019] In one embodiment, the following steps are also included:

[0020] The salt water obtained in S3 is passed into a candied fruit pickling pool to pickle the candied fruit.

[0021] In one embodiment, the following steps are also included:

[0022] The sugar-free desalinated water obtained in S4 through the reverse osmosis membrane concentration equipment is introduced into the concentrated water circulation tank, and flows into the concentration chamber of the electrodialysis unit structure through the concentrated water circulation pump, the concentrated water heat exchanger, and the concentrated water safety filter to serve as make-up water for the electrodialysis unit structure.

[0023] In one embodiment, in S3, the first target concentration is ≤2%, and the second target concentration is 5% to 15%.

[0024] In one embodiment, the salt in the preserved fruit pickling wastewater is sodium chloride, and the sugar is sucrose or fructose.

[0025] In one embodiment, the present application also provides a system, which can be used to perform the above-mentioned method for separating and recovering salt and sugar in preserved fruit pickling wastewater, including wastewater storage equipment, fresh water supply equipment, a pretreatment unit, an electrodialysis unit system, and a reverse osmosis membrane concentration system, wherein:

[0026] The pretreatment unit includes a pH adjustment device, a precipitation and clarification device, and a filtering device;

[0027] The electrodialysis unit system comprises an electrodialysis unit structure, a material circulation structure, and a concentrated water circulation structure;

[0028] The electrodialysis unit structure comprises at least one electrodialysis unit, wherein the electrodialysis unit is provided with a desalination chamber and a concentration chamber which are spaced apart from each other and have independent water inlets and outlets, and polar water chambers which are provided with polar water inlets and outlets at both ends of the electrodialysis unit, and an anion membrane and a cation membrane which are spaced apart from each other between the desalination chamber and the concentration chamber;

[0029] The material circulation structure includes a material circulation water tank, a material circulation pump, a material heat exchanger, and a material safety filter;

[0030] The concentrated water circulation structure includes a concentrated water circulation water tank, a concentrated water circulation water pump, a concentrated water heat exchanger, and a concentrated water safety filter;

[0031] The reverse osmosis membrane concentration system comprises a reverse osmosis water inlet tank, a membrane concentration unit, reverse osmosis produced water storage and water supply equipment and a sugar-containing concentrate tank;

[0032] Specifically, the water outlet of the wastewater storage device is connected to the water inlet of the pretreatment device, the water outlet of the pretreatment device is connected to the water inlet of the material circulation water tank of the material circulation structure, the water outlet of the material circulation water tank is connected to the inlet of the material circulation pump, the outlet of the material circulation pump is connected to the inlet of the material heat exchanger, the outlet of the material heat exchanger is connected to the inlet of the material security filter, the outlet of the material security filter is connected to the water inlet of the desalination chamber of the electrodialysis unit, the water outlet of the desalination chamber of the electrodialysis unit is connected to the return inlet of the material circulation water tank, the discharge port of the material circulation water tank is connected to the inlet of the fresh water discharge pump, the outlet of the fresh water discharge pump is connected to the water inlet of the reverse osmosis water inlet tank, the water outlet of the reverse osmosis water inlet tank is connected to the membrane concentration unit, the water production outlet of the membrane concentration unit is connected to the reverse osmosis water production storage and water supply equipment, and the sugar concentrate outlet of the membrane concentration unit is connected to the sugar-containing concentrate tank;

[0033] The fresh water supply equipment is connected to the water inlet of the concentrated water circulation water tank of the concentrated water circulation structure, the water outlet of the concentrated water circulation water tank is connected to the inlet of the concentrated water circulation pump, the outlet of the concentrated water circulation pump is connected to the inlet of the concentrated water heat exchanger, the outlet of the concentrated water heat exchanger is connected to the inlet of the concentrated water safety filter, the outlet of the concentrated water safety filter is connected to the water inlet of the concentration chamber of the electrodialysis unit, and the water outlet of the concentration chamber is connected to the return inlet of the concentrated water circulation water tank.

[0034] In one embodiment, the reverse osmosis produced water storage and water supply equipment is connected to the concentrated water circulation water tank of the concentrated water circulation structure.

[0035] In one embodiment, the system also includes a concentrated brine preparation system and a preserved fruit pickling pool, the discharge port of the concentrated water circulation tank is connected to the inlet of the concentrated water discharge pump, the outlet of the discharge pump is connected to the concentrated brine preparation system, and the concentrated brine preparation system is connected to the preserved fruit pickling pool.

[0036] In one embodiment, the system further comprises a preserved fruit pickling tank, the discharge port of the concentrated water circulation tank is connected to the inlet of the concentrated water discharge pump, and the outlet of the discharge pump is connected to the preserved fruit pickling tank.

[0037] In one embodiment, the electrodialysis unit structure is composed of a plurality of electrodialysis units connected in parallel.

[0038] The beneficial effects of this application are:

[0039] The present application passes wastewater containing sugar and salt through a desalination chamber of an electrodialysis unit structure, and passes fresh water into a concentration chamber of the electrodialysis unit structure, so that anions and cations dissociated in the wastewater pass through an anion membrane and a cation membrane in the electrodialysis unit structure and enter the concentration chamber in the electrodialysis unit structure, while sugars in the wastewater that cannot be dissociated remain in the desalination chamber of the electrodialysis unit structure because they cannot pass through anion membranes and cation membranes, thereby achieving separation of sugar and salt in the wastewater and improving the efficiency of sugar-salt separation.

[0040] In the present application, the salt-containing concentrated water obtained through the electrodialysis unit structure is directly connected to the concentrated brine preparation system, so that the salt-containing concentrated water of appropriate concentration can be prepared according to actual use, thereby achieving rational use of resources.

[0041] The present application realizes the recycling and reuse of sugar resources by connecting the sugar-rich fresh water obtained through the electrodialysis unit structure with the reverse osmosis membrane concentration equipment.

[0042] The present application connects the fresh water produced in the reverse osmosis membrane concentration device with the concentrated water circulation tank in the electrodialysis unit structure to serve as water replenishment for the circulating concentrated water in the electrodialysis unit structure, thereby reasonably utilizing and saving water resources to the greatest extent.

[0043] The system provided in the present application integrates wastewater storage equipment, fresh water supply equipment, pretreatment equipment, electrodialysis unit structure, reverse osmosis membrane concentration equipment, etc., and has the function of separating sugar and salt from pickling wastewater while recycling and reusing them, thereby greatly improving the treatment efficiency of pickling wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0045] Figure 1 A method flow chart of an embodiment of the present application;

[0046] Figure 2 This is a schematic diagram of a process flow of an embodiment of the present application;

[0047] Figure 3 This is a schematic diagram of the structure of an electrodialysis unit according to an embodiment of the present application;

[0048] Figure 4 This is a schematic diagram of the system structure of an embodiment of the present application for implementing the process flow.

[0049] 1. Wastewater storage equipment; 2. Pretreatment unit; 3. Material circulation water tank; 4. Material circulation pump 4; 5. Material heat exchanger; 6. Material safety filter; 7. Electrodialysis unit structure; 8. Brine safety filter; 9. Brine heat exchanger; 10. Brine circulation pump; 11. Fresh water supply equipment; 12. Brine circulation water tank; 13. Brine discharge pump; 14. Preserved fruit pickling pool; 15. Brine preparation system; 16. Fresh water discharge pump; 17. Reverse osmosis water inlet tank; 18. Membrane concentration unit; 19. Sugar concentrate tank; 20. Reverse osmosis water storage and supply equipment. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0051] Figure 1 A method flow chart of an embodiment of the present application is shown. Figure 2 A schematic diagram of a process flow for separating and recovering salt and sugar from preserved fruit pickling wastewater according to an embodiment of the present application is shown, wherein the salt in the pickling wastewater is sodium chloride, and the sugar is sucrose and fructose, and specifically comprises the following steps:

[0052] Step 1: pretreating the wastewater from pickled fruit, including adjusting the pH of the wastewater so that the pH value in the wastewater is ≥4, and precipitating, clarifying and filtering the wastewater so that the suspended matter in the wastewater is <1 mg / L, thereby reducing the corrosiveness of the wastewater and meeting the requirements of electrodialysis water inlet.

[0053] Step 2: Preliminarily separate the salt and sugar in the wastewater from pickled fruits. The pretreated wastewater from pickled fruits is passed into the desalination chamber in the electrodialysis unit structure 7. At the same time, the initial use water is passed into the concentration chamber in the electrodialysis unit structure 7. The salt water and the sugar-containing fresh water are separated by the anion exchange membrane and the cation exchange membrane arranged at intervals in the electrodialysis unit, thereby preliminarily separating the sugar and salt from the wastewater from pickled fruits.

[0054] Specifically, the pretreated pickled fruit wastewater is introduced into the material circulation water tank 3 in the electrodialysis unit system, and the initial water is injected into the concentrated water circulation water tank 12 in the electrodialysis unit system. The initial water is fresh water (such as tap water, purified water and other water of equivalent water quality). The amount of the initial water is determined according to the salt concentration in the pickled fruit wastewater to be treated and the concentration of the concentrated brine required in the actual application. The pickled fruit wastewater passes through the material circulation water tank 3 and then enters the desalination chamber in the electrodialysis unit structure 7 through the material circulation pump 4, the material heat exchanger 5 and the material security filter 6. The initial water passes through the concentrated water circulation water tank 12 and then enters the concentration chamber in the electrodialysis unit structure 7 through the concentrated water circulation pump 10, the concentrated water heat exchanger 9 and the concentrated water security filter 8. Since only the initial water, i.e. fresh water or circulating concentrated water, is introduced into the concentration chamber, the sugars in the pickled fruit wastewater cannot enter the concentration chamber in the electrodialysis unit, but can only stay in the electrodialysis unit. More specifically, the dissociated positive and negative ions in the wastewater from pickled fruits enter the concentrating chamber in the electrodialysis unit structure 7 through the anion membrane and the cation membrane in the electrodialysis unit structure 7, thereby producing salt-rich water, while the undissociated sugar in the wastewater from pickled fruits cannot pass through the anion membrane and the cation membrane and remains in the desalting chamber. At the same time, since part of the water in the concentrating chamber flows out of the concentrating chamber through the anion membrane and the cation membrane in the electrodialysis unit structure 7, the sugar in the desalting chamber is further concentrated.

[0055] Step three, complete the separation of salt and sugar in the wastewater of pickled fruit, return the sugar-containing fresh water obtained in step two to the material circulation water tank 3, and the salt water flows into the concentrated water circulation water tank 12, and the sugar-containing fresh water and the salt water are circulated in the electrodialysis unit structure 7 through the material circulation pump 4 and the concentrated water circulation pump 10 respectively, so that the positive and negative ions in the sugar-containing fresh water continuously enter the concentration chamber until it is detected that the salt content of the sugar-containing fresh water in the material circulation water tank 3 is reduced to the first target concentration, and the salt content of the salt water in the concentrated water circulation water tank 12 is increased to the second target concentration, thereby completing the separation of salt and sugar in the wastewater of pickled fruit.

[0056] Step 4, concentrating the sugar-containing fresh water, reducing the salt content of the sugar-containing fresh water obtained in step 3 to the first target concentration, and discharging the sugar-containing fresh water from the material circulation water tank 3 through the fresh water discharge pump 16 to the reverse osmosis water inlet tank 17 in the reverse osmosis membrane concentration device, and concentrating the sugar-free desalinated water and the sugar-containing concentrated liquid through the membrane concentration unit 18, thereby achieving the concentration of the sugar-containing fresh water. The sugar-containing concentrated liquid can be used as a biochemical nutrient solution, or for other purposes.

[0057] In one embodiment, the first target concentration is ≤2%, and the second target concentration is 5%-15%.

[0058] In one embodiment, when the circulating water temperature increases with the operation of the electrodialysis system, circulating cooling water is introduced into the material heat exchanger 5 and the concentrated water heat exchanger 9 for cooling, and the water temperature of each water stream in the electrodialysis system is controlled between 15-40°C.

[0059] In one embodiment, when the salt content of the brine in the concentrated water circulation tank is increased to the second target concentration, the brine can be directly introduced into the preserved fruit pickling pool 14 to pickle the preserved fruits.

[0060] In one embodiment, when the salt content of the brine in the concentrated water circulation tank is increased to the second target concentration, the brine is passed through the concentrated water discharge pump 13 into the concentrated brine preparation system 15, and the brine is prepared to achieve recycling. The concentrated brine preparation system 15, according to the actual use, prepares the concentration of the brine by feeding a certain amount of sodium chloride. In one embodiment, the prepared brine can be passed into the preserved fruit pickling pool 14 to pickle preserved fruits. Of course, it can also be used for other purposes.

[0061] In one embodiment, the sugar-free desalinated water obtained in step four through the reverse osmosis membrane concentration equipment is introduced into the concentrated water circulation tank 12, and flows into the concentration chamber of the electrodialysis unit structure 7 through the concentrated water circulation pump 10, the concentrated water heat exchanger 9, and the concentrated water safety filter 8 to serve as make-up water for the electrodialysis unit structure 7.

[0062] In one embodiment, the filtration in step 1 includes but is not limited to medium filtration, ultrafiltration, microfiltration, etc. In addition, in order to ensure a better separation effect, other pretreatment measures can be added according to different wastewaters to be treated, such as flotation, advanced oxidation, MBR and other treatment measures.

[0063] Figure 2 This is a schematic diagram of the electrodialysis unit structure 7 of an embodiment of the present application, in which a desalination chamber and a concentration chamber with independent water inlets and outlets are arranged at intervals from each other, and polar water chambers with polar water inlets and outlets are arranged at both ends of the electrodialysis unit, and anion membranes and cation membranes are arranged at intervals from each other between the desalination chamber and the concentration chamber.

[0064] Figure 3 A system structure diagram for implementing the above process flow is shown, including wastewater storage equipment, fresh water supply equipment 11, pretreatment unit 2, electrodialysis unit system, reverse osmosis membrane concentration system, wherein:

[0065] The pretreatment unit 2 includes a pH adjustment device, a precipitation and clarification device, and a filtering device;

[0066] The electrodialysis unit system includes an electrodialysis unit structure 7, a material circulation structure, and a concentrated water unit structure;

[0067] The electrodialysis unit structure 7 comprises at least one electrodialysis unit, wherein the electrodialysis unit is provided with a desalination chamber and a concentration chamber which are spaced apart from each other and have independent water inlets and outlets, and polar water chambers which are provided at both ends of the electrodialysis unit and have polar water inlets and outlets, and an anion membrane and a cation membrane which are spaced apart from each other between the desalination chamber and the concentration chamber;

[0068] The material circulation structure includes a material circulation water tank 3, a material circulation pump 4, a material heat exchanger 5, and a material safety filter 6;

[0069] The concentrated water circulation structure includes a concentrated water circulation water tank 12, a concentrated water circulation water pump, a concentrated water heat exchanger 9, and a concentrated water safety filter 8;

[0070] The reverse osmosis membrane concentration system includes a reverse osmosis water inlet tank 17, a membrane concentration unit 18, a reverse osmosis produced water storage and supply device 20 and a sugar-containing concentrate tank 19;

[0071] Specifically, the water outlet of the wastewater storage device 1 is connected to the water inlet of the pretreatment device, the water outlet of the pretreatment device is connected to the water inlet of the material circulation water tank 3 of the material circulation structure, the water outlet of the material circulation water tank 3 is connected to the inlet of the material circulation pump 4, the outlet of the material circulation pump 4 is connected to the inlet of the material heat exchanger 5, the outlet of the material heat exchanger 5 is connected to the inlet of the material security filter 6, the outlet of the material security filter 6 is connected to the water inlet of the desalination chamber of the electrodialysis unit, the water outlet of the desalination chamber of the electrodialysis unit is connected to the return inlet of the material circulation water tank 3, the discharge port of the material circulation water tank 3 is connected to the inlet of the fresh water discharge pump 16, the outlet of the fresh water discharge pump 16 is connected to the water inlet of the reverse osmosis water inlet tank 17, the water outlet of the reverse osmosis water inlet tank 17 is connected to the membrane concentration unit 18, the water production outlet of the membrane concentration unit 18 is connected to the reverse osmosis water production storage and water supply equipment 20, and the sugar concentrate outlet of the membrane concentration unit 18 is connected to the sugar-containing concentrate tank 19;

[0072] The fresh water supply equipment 11 is connected to the water inlet of the concentrated water circulation water tank 12 of the concentrated water circulation structure, the water outlet of the concentrated water circulation water tank 12 is connected to the inlet of the concentrated water circulation pump 10, the outlet of the concentrated water circulation pump 10 is connected to the inlet of the concentrated water heat exchanger 9, the outlet of the concentrated water heat exchanger 9 is connected to the inlet of the concentrated water safety filter 8, the outlet of the concentrated water safety filter 8 is connected to the water inlet of the concentration chamber of the electrodialysis unit, and the water outlet of the concentration chamber is connected to the return inlet of the concentrated water circulation water tank 12.

[0073] In one embodiment, the reverse osmosis produced water storage and supply equipment 20 is connected to the concentrated water circulation water tank 12 of the concentrated water circulation structure.

[0074] In one embodiment, the system also includes a concentrated brine preparation system 15 and a preserved fruit pickling pool 14, the discharge port of the concentrated water circulation tank 12 is connected to the inlet of the concentrated water discharge pump 13, the outlet of the discharge pump is connected to the concentrated brine preparation equipment, and the concentrated brine preparation system 15 is connected to the preserved fruit pickling pool 14.

[0075] In one embodiment, the system further comprises a preserved fruit pickling pool 14 , the discharge port of the concentrated water circulating water tank 12 is connected to the inlet of the concentrated water discharge pump 13 , and the outlet of the discharge pump is connected to the preserved fruit pickling pool 14 .

[0076] In one embodiment, the electrodialysis unit structure 7 is composed of a plurality of electrodialysis units connected in parallel.

[0077] In one embodiment, the reverse osmosis membrane concentration system uses the anti-fouling FORTILIFE XC70 reverse osmosis membrane.

[0078] The present application provides an embodiment in which preserved fruits are pickled with salt and sugar to produce 600L of preserved fruit pickling wastewater, wherein the preserved fruit pickling wastewater contains 15% (90kg) of sodium chloride and 5% (30kg) of sugar.

[0079] Firstly, the wastewater from pickled fruits is passed into the pretreatment equipment, and after pH adjustment, precipitation, clarification and filtration, the suspended solids in the wastewater are less than 1 mg / L, the free residual chlorine is less than 0.5 mg / L, and the pH value is between 6 and 9.

[0080] Then, the pretreated preserved fruit wastewater is passed into the material circulation water tank 3 in the electrodialysis unit system, and 385.8L of initial water is injected into the concentrated water circulation water tank 12 in the electrodialysis unit system. The initial water is fresh water. The preserved fruit wastewater passes through the material circulation pump 4, the material heat exchanger 5, the material security filter 6, and then enters the desalination chamber in the electrodialysis unit structure 7, and does not enter the concentration chamber in the electrodialysis unit structure 7. The initial water passes through the concentrated water circulation pump 10, the concentrated water heat exchanger 9, the concentrated water security filter 8, and then enters the concentration chamber in the electrodialysis unit structure 7. In this way, the sodium ions and chloride ions in the preserved fruit wastewater pass through the anion and cation membranes in the electrodialysis unit structure 7, respectively, and enter the concentration chamber in the electrodialysis unit structure 7 to obtain salt water, while the sugar in the preserved fruit wastewater cannot pass through the anion and cation membranes and continues to stay in the desalination chamber in the electrodialysis unit structure 7 to obtain sugar-containing fresh water.

[0081] Next, the sugar-containing fresh water returns to the material circulation water tank 3, while the salt water flows into the concentrated water circulation water tank 12. The sugar-containing fresh water and the salt water circulate in the electrodialysis unit structure 7 through the material circulation pump 4 and the concentrated water circulation pump 10 respectively, so that the sodium ions and chloride ions in the sugar-containing fresh water continuously enter the concentration chamber until it is detected that the sugar-containing fresh water in the material circulation water tank 3 contains 1.00% sodium chloride and 11.22% sugar, while the salt water in the concentrated water circulation water tank 12 contains 12% sodium chloride.

[0082] At this time, the sugar-containing desalinated water (11.22% sugar, 1.00% sodium chloride) obtained above is discharged from the material circulation water tank 3 through the fresh water discharge pump 16 to the reverse osmosis water inlet tank 17 in the reverse osmosis membrane concentration system, and concentrated by the membrane concentration unit 18, which uses the anti-pollution FORTILIFE XC70 reverse osmosis membrane, thereby producing 100L of sugar-free fresh water and 146L of sugar-containing concentrate, which contains 18.90% sugar and 1.68% sodium chloride. The sugar-free desalinated water produced by the reverse osmosis membrane concentration system is passed into the concentrated water circulation water tank 12 of the electrodialysis unit as a supplement to the concentrated water circulation structure and is circulated.

[0083] The salt water in the concentrated water circulation tank 12 is directly introduced into the preserved fruit pickling pool 14 through the concentrated water discharge pump 13 to pickle the preserved fruit.

[0084] The water production indicators of each unit in this embodiment are tested and shown in the following table:

[0085]

[0086] From the above data, it can be seen that after the system treatment of separating and recovering salt and sugar in the wastewater of preserved fruit pickling, 87.54 kg of salt and 27.6 kg of sugar were recovered in the wastewater, and the recovery rates of salt and sugar were both above 90%.

[0087] It should be noted that the concentrated brine preparation device and reverse osmosis membrane concentration system mentioned in this application are both existing conventional systems / equipment, and their structures will not be described in detail here.

[0088] It should be noted that, according to actual operational requirements, multiple groups of electrodialysis unit systems in the present application can be used in parallel, and multiple groups of electrodialysis unit structures in the electrodialysis unit system in the present application can also be used in series at the same time.

[0089] The above is only a preferred embodiment of the present application. It should be noted that, for ordinary technicians in this technical field, without departing from the principle of the present application, several improvements and modifications can be made. For example, multiple electrodialysis units are operated in series, and the preserved fruit pickling wastewater is sequentially passed through the electrodialysis unit structure composed of the multiple electrodialysis units in series to further desalinate the sugar-containing fresh water and increase the salinity of the salt water. These improvements and modifications should also be regarded as the protection scope of the present application.

Claims

1. A method for separating and recovering salt and sugar from preserved fruit pickling wastewater, characterized in that: The following steps are involved: S1, pretreatment of preserved fruit wastewater: adjusting the pH value of preserved fruit wastewater to make the pH value of preserved fruit wastewater ≥4, precipitating and clarifying the preserved fruit wastewater, filtering the preserved fruit wastewater, making the suspended matter in the preserved fruit wastewater meet the requirement of <1mg / L, so as to meet the requirements of electrodialysis water inlet; S2, preliminary separation of salt and sugar in the wastewater of preserved fruit: the pretreated wastewater of preserved fruit is introduced into the material circulation water tank (3) in the electrodialysis unit system, and at the same time, initial water is injected into the concentrated water circulation water tank (12) in the electrodialysis unit system, wherein the initial water is fresh water, wherein the wastewater of preserved fruit passes through the material circulation water tank (3) and then sequentially passes through the material circulation pump (4), the material heat exchanger (5) and the material security filter (6) into the desalination chamber in the electrodialysis unit structure (7). The initial water passes through the concentrated water circulation tank (12), the concentrated water circulation pump (10), the concentrated water heat exchanger (9) and the concentrated water security filter (8) and enters the concentration chamber in the electrodialysis unit structure (7), so that the positive and negative ions in the preserved fruit wastewater pass through the anion membrane and the cation membrane in the electrodialysis unit structure (7) respectively and enter the concentration chamber in the electrodialysis unit structure (7) to obtain salt water, while the sugar in the preserved fruit wastewater continues to stay in the desalination chamber in the electrodialysis unit structure (7) to obtain sugar-containing fresh water; S3, completing the separation of salt and sugar in the wastewater from pickled fruits: the sugar-containing fresh water obtained in S2 is returned to the material circulation water tank (3), and the salt water flows into the concentrated water circulation water tank (12). The sugar-containing fresh water and the salt water are circulated in the electrodialysis unit structure (7) through the material circulation pump (4) and the concentrated water circulation pump (10) respectively, so that the positive and negative ions in the sugar-containing fresh water continuously enter the concentration chamber until it is detected that the salt content of the sugar-containing fresh water in the material circulation water tank (3) is reduced to the first target concentration, and the salt content of the salt water in the concentrated water circulation water tank (12) is increased to the second target concentration, so as to complete the separation of salt and sugar in the wastewater from pickled fruits; S4, concentrating the sugar-containing fresh water: the sugar-containing fresh water obtained in S3, the salt content of which is reduced to the first target concentration, is discharged from the material circulation water tank (3) through the fresh water discharge pump (16) to the reverse osmosis water inlet tank (17) in the reverse osmosis membrane concentration system, and is concentrated through the membrane concentration unit (18), thereby obtaining sugar-free desalinated water and sugar-containing concentrated liquid, thereby achieving the concentration of the sugar-containing fresh water.

2. A method for separating and recovering salt and sugar from preserved fruit pickling wastewater as claimed in claim 1, characterized in that: The following steps are also included: The salt water obtained in S3 is raised to a second target concentration and is introduced into a concentrated brine preparation system (15) via a concentrated water discharge pump (13) to adjust the salt content in the brine for recycling.

3. A method for separating and recovering salt and sugar from preserved fruit pickling wastewater as claimed in claim 1, characterized in that: The following steps are also included: The salt water obtained in S3 is passed into a candied fruit pickling pool (14) to pickle the candied fruit.

4. A method for separating and recovering salt and sugar from preserved fruit pickling wastewater as claimed in claim 1, characterized in that: The following steps are also included: The sugar-free desalinated water obtained in S4 through the reverse osmosis membrane concentration system is introduced into the concentrated water circulation tank (12), and then flows into the concentration chamber of the electrodialysis unit structure (7) through the concentrated water circulation pump (10), the concentrated water heat exchanger (9), and the concentrated water safety filter (8) to serve as make-up water for the electrodialysis unit structure (7).

5. A method for separating and recovering salt and sugar from preserved fruit pickling wastewater as claimed in claim 1, characterized in that: In S3, the first target concentration is ≤2%, and the second target concentration is 5% to 15%.

6. A method for separating and recovering salt and sugar from preserved fruit pickling wastewater as claimed in claim 1, characterized in that: Also includes: The salt in the preserved fruit pickling wastewater is sodium chloride, and the sugar is sucrose or fructose.

7. A system can be used to implement the method for separating and recovering salt and sugar from preserved fruit pickling wastewater as described in any one of claims 1 to 6, characterized in that: The invention comprises a wastewater storage device (1), a freshwater supply device (11), a pretreatment unit (2), an electrodialysis unit system, and a reverse osmosis membrane concentration system, wherein: The pretreatment unit (2) includes a pH adjustment device, a precipitation and clarification device, and a filtering device; the electrodialysis unit system includes an electrodialysis unit structure (7), a material circulation structure, and a concentrated water circulation structure; The electrodialysis unit structure (7) comprises at least one electrodialysis unit, wherein the electrodialysis unit is provided with a desalination chamber and a concentration chamber which are spaced apart from each other and have independent water inlets and outlets, and polar water chambers which are provided at both ends of the electrodialysis unit and have polar water inlets and outlets, and an anion membrane and a cation membrane which are spaced apart from each other between the desalination chamber and the concentration chamber; The material circulation structure comprises a material circulation water tank (3), a material circulation pump (4), a material heat exchanger (5), and a material safety filter (6); The concentrated water circulation structure comprises a concentrated water circulation water tank (12), a concentrated water circulation pump (10), a concentrated water heat exchanger (9), and a concentrated water safety filter (8); The reverse osmosis membrane concentration system comprises a reverse osmosis water inlet tank (17), a membrane concentration unit (18), a reverse osmosis produced water storage and water supply device (20) and a sugar-containing concentrate tank (19); Specifically, the water outlet of the wastewater storage device (1) is connected to the water inlet of the pretreatment device, the water outlet of the pretreatment device is connected to the water inlet of the material circulation water tank (3) of the material circulation structure, the water outlet of the material circulation water tank (3) is connected to the inlet of the material circulation pump (4), the outlet of the material circulation pump (4) is connected to the inlet of the material heat exchanger (5), the outlet of the material heat exchanger (5) is connected to the inlet of the material security filter (6), and the outlet of the material security filter (6) is connected to the water inlet of the desalination chamber of the electrodialysis unit. The water outlet of the desalination chamber of the electrodialysis unit is connected to the return inlet of the material circulation water tank (3), the discharge port of the material circulation water tank (3) is connected to the inlet of the fresh water discharge pump (16), the outlet of the fresh water discharge pump (16) is connected to the water inlet of the reverse osmosis water inlet tank (17), the water outlet of the reverse osmosis water inlet tank (17) is connected to the membrane concentration unit (18), the water output outlet of the membrane concentration unit (18) is connected to the reverse osmosis water output storage and water supply equipment (20), and the sugar concentrate outlet of the membrane concentration unit (18) is connected to the sugar concentrate tank (19); The fresh water supply equipment (11) is connected to the water inlet of the concentrated water circulation tank (12) of the concentrated water circulation structure, the water outlet of the concentrated water circulation tank (12) is connected to the inlet of the concentrated water circulation pump (10), the outlet of the concentrated water circulation pump (10) is connected to the inlet of the concentrated water heat exchanger (9), the outlet of the concentrated water heat exchanger (9) is connected to the inlet of the concentrated water safety filter (8), the outlet of the concentrated water safety filter (8) is connected to the water inlet of the concentration chamber of the electrodialysis unit, and the water outlet of the concentration chamber is connected to the return inlet of the concentrated water circulation tank (12).

8. A system according to claim 7, characterized in that The reverse osmosis produced water storage and supply equipment (20) is connected to the concentrated water circulation water tank (12) of the concentrated water circulation structure.

9. A system according to claim 7, characterized in that The system further comprises a concentrated brine preparation system (15) and a preserved fruit pickling pool (14); the discharge port of the concentrated water circulation tank (12) is connected to the inlet of a concentrated water discharge pump (13); the outlet of the concentrated water discharge pump (13) is connected to the concentrated brine preparation system (15); and the concentrated brine preparation system (15) is connected to the preserved fruit pickling pool (14).

10. A system according to claim 7, characterized in that The electrodialysis unit structure (7) is composed of a plurality of electrodialysis units connected in parallel.

Images