Wastewater concentration system and method coupling forward osmosis with evaporative crystallization

Abstract

This invention provides a wastewater concentration system and method coupled with forward osmosis and evaporation crystallization. The wastewater concentration system includes an organic wastewater pretreatment unit, a biochemical treatment unit, a membrane concentration unit, an evaporation crystallization unit, and a forward osmosis concentration unit. The wastewater concentration system provided by this invention removes impurities from organic wastewater through filtration in the organic wastewater pretreatment unit; treats wastewater through the biochemical treatment unit, membrane concentration unit, and evaporation crystallization equipment to obtain evaporation crystallization mother liquor; pretreats the mother liquor through the mother liquor treatment equipment to remove organic matter, hardness, and suspended solids, obtaining a driving fluid and simultaneously enabling the rational utilization of the mother liquor to reduce disposal costs; and concentrates organic wastewater through the forward osmosis concentration unit. Compared with other membrane concentration processes, forward osmosis membranes exhibit less fouling, and the concentrated solution has a high organic matter concentration and small volume, effectively reducing environmental pollution and energy consumption.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a wastewater concentration system and method that couples forward osmosis and evaporation crystallization. Background Technology

[0002] Wastewater treatment is of great significance for both environmental protection and water resource reuse. Biochemical effluent from coking wastewater can achieve zero discharge after membrane concentration and evaporative crystallization. However, during the evaporative crystallization concentration process, the solution changes from unsaturated to saturated, organic matter and other ions are continuously concentrated, and the boiling point of the material continuously increases. The last portion of the mother liquor is difficult to evaporate further and is discharged from the evaporator as evaporative crystallization mother liquor. Treating evaporative crystallization mother liquor with high salt and high organic matter content is difficult; if it is directly evaporated to dryness, the resulting mixed salts will be hazardous waste, with extremely high treatment costs.

[0003] In addition, some wastewater or solutions containing high levels of organic matter can be treated using forward osmosis. Forward osmosis is a membrane separation process driven by osmotic pressure, where water spontaneously diffuses through a selective semi-permeable membrane from a region of higher hydrochemical potential (or low osmotic pressure side) to a region of lower hydrochemical potential (or high osmotic pressure side). The driving force of forward osmosis is the osmotic pressure difference between the driving fluid and the feed solution; no external pressure is required. Compared to traditional membrane separation technologies, forward osmosis has advantages such as less membrane fouling, no need for external pressure, and low energy consumption, making it widely applicable in water treatment, seawater desalination, and food and beverage industries. However, the key to successful forward osmosis is the need for a high-flux, recyclable driving fluid.

[0004] Furthermore, beer wastewater can serve as a supplementary carbon source for wastewater treatment. It contains large amounts of sugars, proteins, starches, alcohols, and pectins, with a COD concentration of 2000–3000 mg / L. Utilizing beer wastewater as a supplementary carbon source has a synergistic effect of pollution reduction and carbon reduction. However, to ensure the carbon source needs of the wastewater treatment plant are met, the amount of beer wastewater added is relatively large, which may impact the water quality and quantity of the biological treatment system and also increase transportation costs. Summary of the Invention

[0005] The purpose of this invention is to provide a wastewater concentration system and method that couples forward osmosis and evaporation crystallization, in order to solve one or more of the problems existing in the prior art, such as the difficulty in treating the mother liquor of evaporation crystallization, the need for a driving fluid for forward osmosis, and the potential impact of large volumes of beer wastewater as a carbon source on the biochemical system and increased transportation costs.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a wastewater concentration system coupled with forward osmosis and evaporation crystallization, comprising: an organic wastewater pretreatment unit, a biochemical treatment unit, a membrane concentration unit, an evaporation crystallization unit, and a forward osmosis concentration unit; the organic wastewater pretreatment unit is used to filter organic wastewater; the biochemical treatment unit is used to perform biochemical treatment on wastewater; the membrane concentration unit is used to concentrate the biochemical effluent from the biochemical treatment unit; the evaporation crystallization unit includes an evaporation crystallization device and a mother liquor treatment device; the evaporation crystallization device is configured to perform evaporation crystallization treatment on the effluent from the membrane concentration unit to obtain an evaporation crystallization mother liquor; The mother liquor treatment equipment is configured to pretreat the evaporation crystallization mother liquor to obtain an evaporation crystallization mother liquor driving liquid; the forward osmosis concentration unit has an inlet, a liquid inlet, an outlet, and a liquid outlet, the inlet being connected to the organic wastewater pretreatment unit to receive the filtered organic wastewater, the liquid inlet being connected to the liquid outlet of the mother liquor treatment equipment to receive the evaporation crystallization mother liquor driving liquid; the forward osmosis concentration unit is configured to concentrate the filtered organic wastewater and dilute the evaporation crystallization mother liquor driving liquid, the outlet being used to discharge the concentrated organic wastewater, and the liquid outlet being used to discharge the diluted evaporation crystallization mother liquor driving liquid.

[0007] Optionally, the organic wastewater pretreatment unit includes a bar screen, a hydraulic screen, and a primary sedimentation tank arranged in sequence.

[0008] Optionally, the biochemical treatment unit includes a primary anoxic tank, a primary aerobic tank, a secondary anoxic tank, and a secondary aerobic tank arranged sequentially, with the secondary anoxic tank connected to the outlet.

[0009] Optionally, the outlet of the forward osmosis concentration unit is connected to the membrane concentration unit.

[0010] Optionally, the outlet is equipped with a control valve, which is configured to control the diluent to be discharged into the membrane concentration unit when the ratio of the salt content of the evaporation crystallization mother liquor to the salt content of the diluent reaches a preset range.

[0011] Optionally, the preset range is 0.2 to 0.5.

[0012] Optionally, the membrane concentration unit includes a reverse osmosis unit, a nanofiltration desalination unit, a high-pressure reverse osmosis unit, and an electrodialysis unit connected in sequence, with the outlet connected to the nanofiltration desalination unit.

[0013] Optionally, the mother liquor treatment equipment includes an advanced oxidation device, a chemical precipitation device, and a filtration device arranged in sequence.

[0014] To achieve the above objectives, the present invention also provides a wastewater concentration method coupled with forward osmosis and evaporation crystallization, wherein the wastewater concentration method is used in the wastewater concentration system coupled with forward osmosis and evaporation crystallization as described in any one of the above claims, and the wastewater concentration method includes:

[0015] The organic wastewater is transported to the organic wastewater pretreatment unit for filtration, and the filtered organic wastewater is then transported to the forward osmosis concentration unit through the inlet of the forward osmosis concentration unit.

[0016] Wastewater is transported to the biochemical treatment unit for biochemical treatment to obtain biochemical effluent;

[0017] The biochemical effluent is transported to the membrane concentration unit for membrane concentration treatment to obtain membrane concentrated water.

[0018] The concentrated water from the membrane is transported to the evaporation crystallization equipment for evaporation crystallization to obtain evaporation crystallization mother liquor;

[0019] The evaporation crystallization mother liquor is transported to the mother liquor treatment equipment for mother liquor pretreatment to obtain evaporation crystallization mother liquor driving liquid, and the evaporation crystallization mother liquor driving liquid is transported to the forward osmosis concentration unit through the liquid inlet of the forward osmosis concentration unit;

[0020] The filtered organic wastewater is concentrated and the evaporation crystallization mother liquor driving liquid is diluted;

[0021] Discharge the concentrated organic wastewater;

[0022] The diluted solution of the evaporation crystallization mother liquor driving liquid is discharged.

[0023] Optionally, the wastewater concentration method further includes:

[0024] The concentrated organic wastewater is discharged into the biochemical treatment unit;

[0025] The diluted solution of the evaporation crystallization mother liquor driving liquid is discharged into the membrane concentration unit.

[0026] Compared with existing technologies, the wastewater concentration system and method coupled with forward osmosis and evaporation crystallization provided by this invention have the following advantages:

[0027] The wastewater concentration system coupled with forward osmosis and evaporative crystallization provided by this invention includes: an organic wastewater pretreatment unit, a biochemical treatment unit, a membrane concentration unit, an evaporative crystallization unit, and a forward osmosis concentration unit; the organic wastewater pretreatment unit is used to filter organic wastewater; the biochemical treatment unit is used to perform biochemical treatment on wastewater; the membrane concentration unit is used to concentrate the biochemical effluent from the biochemical treatment unit; the evaporative crystallization unit includes an evaporative crystallization device and a mother liquor treatment device; the evaporative crystallization device is configured to perform evaporative crystallization treatment on the effluent from the membrane concentration unit to obtain an evaporative crystallization mother liquor; the mother liquor treatment device is configured to... The evaporation crystallization mother liquor is pretreated to obtain an evaporation crystallization mother liquor driving liquid. The forward osmosis concentration unit has an inlet, a liquid inlet, an outlet, and a liquid outlet. The inlet is connected to the organic wastewater pretreatment unit to receive the filtered organic wastewater. The liquid inlet is connected to the liquid outlet of the mother liquor treatment equipment to receive the evaporation crystallization mother liquor driving liquid. The forward osmosis concentration unit is configured to concentrate the filtered organic wastewater and dilute the evaporation crystallization mother liquor driving liquid. The outlet is used to discharge the concentrated organic wastewater and the liquid outlet is used to discharge the diluted evaporation crystallization mother liquor driving liquid. Therefore, the wastewater concentration system coupled with forward osmosis and evaporative crystallization provided by this invention filters organic wastewater through an organic wastewater pretreatment unit, removing impurities and laying the foundation for the concentration of organic wastewater in the forward osmosis concentration unit. It treats wastewater through a biochemical treatment unit and a membrane concentration unit, providing a basis for obtaining evaporative crystallization mother liquor. The evaporative crystallization equipment treats the concentrated membrane water to obtain evaporative crystallization mother liquor, providing a basis for obtaining the driving fluid required by the forward osmosis concentration unit. The mother liquor treatment equipment pretreats the evaporative crystallization mother liquor, removing organic matter, hardness, and suspended solids, thus obtaining the driving fluid required by the forward osmosis concentration unit, further laying the foundation for the concentration of organic wastewater in the forward osmosis concentration unit. Simultaneously, it allows for the rational utilization of the evaporative crystallization mother liquor, reducing its disposal costs. Compared with other membrane concentration processes, the forward osmosis membrane exhibits relatively less fouling when concentrating organic wastewater through the forward osmosis concentration unit. Furthermore, the concentrated organic wastewater after forward osmosis treatment has a high organic matter concentration and small volume, effectively reducing environmental pollution and energy consumption.

[0028] Furthermore, the biochemical treatment unit includes a primary anoxic tank, a primary aerobic tank, a secondary anoxic tank, and a secondary aerobic tank arranged sequentially, with the secondary anoxic tank connected to the effluent outlet. Thus, the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided by this invention, by setting up a biochemical treatment unit including a primary anoxic tank, a primary aerobic tank, a secondary anoxic tank, and a secondary aerobic tank, can perform biological denitrification and organic pollutant removal treatment on wastewater. The secondary anoxic tank, acting as a post-denitrification tank, requires periodic addition of a carbon source. By connecting the effluent outlet of the forward osmosis concentration unit to the secondary anoxic tank of the biochemical treatment unit, the concentrated organic wastewater can be reused as a carbon source in the biochemical treatment unit. Moreover, the concentrated organic wastewater after forward osmosis treatment has a high organic matter concentration and small volume, reducing the impact on the biochemical treatment unit and lowering transportation costs. This enables the resource utilization of organic wastewater, forming a circular concentration system for organic wastewater, which has a synergistic effect of pollution reduction and carbon reduction and extremely important environmental protection significance.

[0029] Furthermore, the outlet of the forward osmosis concentration unit is connected to the membrane concentration unit. Therefore, the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided by this invention, by connecting the outlet of the forward osmosis concentration unit to the membrane concentration unit, enables the dilution of the evaporation crystallization mother liquor driving liquid generated by the forward osmosis concentration unit to be reused in the membrane concentration unit, thereby reducing the disposal costs of the dilution of the evaporation crystallization mother liquor driving liquid.

[0030] Since the wastewater concentration method coupled with forward osmosis and evaporation crystallization provided by this invention belongs to the same inventive concept as the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided by this invention, the wastewater concentration method coupled with forward osmosis and evaporation crystallization provided by this invention has at least all the advantages of the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided by this invention. For the advantages of the wastewater concentration method coupled with forward osmosis and evaporation crystallization provided by this invention, please refer to the relevant description of the beneficial effects of the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided by this invention, which will not be repeated here. Attached Figure Description

[0031] Figure 1 This is a structural block diagram of a wastewater concentration system coupled with forward osmosis and evaporation crystallization, provided in Embodiment 1 of the present invention;

[0032] Figure 2 This is a process flow diagram of a wastewater concentration system coupled with forward osmosis and evaporation crystallization, provided in Embodiment 1 of the present invention.

[0033] Figure 3 This is a schematic flowchart of a wastewater concentration method coupled with forward osmosis and evaporation crystallization provided in Embodiment 2 of the present invention;

[0034] The annotations in the attached figures are explained as follows:

[0035] 1-Organic wastewater pretreatment unit, 10-Grate, 11-Hydraulic screen, 12-Primary sedimentation tank, 2-Biological treatment unit, 20-Primary anoxic tank, 21-Primary aerobic tank, 22-Secondary anoxic tank, 23-Secondary aerobic tank, 3-Membrane concentration unit, 30-Reverse osmosis device, 31-Nanofiltration desalination device, 32-High-pressure reverse osmosis device, 33-Electrodialysis device, 4-Evaporation crystallization unit, 40-Evaporation crystallization equipment, 41-Mother liquor treatment equipment, 410-Advanced oxidation device, 411-Chemical precipitation device, 412-Filtration device, 5-Forward osmosis concentration unit, 50-Inlet, 51-Liquid inlet, 52-Outlet, 53-Liquid outlet. Detailed Implementation

[0036] The wastewater concentration system and method coupled with forward osmosis and evaporation crystallization proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, only for the purpose of conveniently and clearly illustrating the embodiments of this invention. Please refer to the drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for the purpose of assisting those skilled in the art to understand and read, and are not intended to limit the implementation conditions of this invention. Any modifications to the structure, changes in proportions, or adjustments to the size, if they are the same as or similar to the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention. Specific design features of the invention disclosed herein, including, for example, specific dimensions, orientations, positions, and shapes, will be determined in part by the specific application and usage environment. Furthermore, in the embodiments described below, sometimes the same reference numerals are used in different drawings to indicate the same parts or parts with the same function, and their repeated descriptions are omitted.

[0037] Example 1

[0038] This embodiment provides a wastewater concentration system that couples forward osmosis with evaporation and crystallization. For details, please refer to... Figure 1 and Figure 2 , Figure 1 This is a structural block diagram of the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided in this embodiment; Figure 2 This is a process flow diagram of the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided in this embodiment. From... Figure 1 and Figure 2As can be seen, the wastewater concentration system includes: an organic wastewater pretreatment unit 1, a biochemical treatment unit 2, a membrane concentration unit 3, an evaporation crystallization unit 4, and a forward osmosis concentration unit 5; the organic wastewater pretreatment unit 1 is used to filter organic wastewater; the biochemical treatment unit 2 is used to perform biochemical treatment on wastewater; the membrane concentration unit 3 is used to perform membrane concentration on the biochemical effluent from the biochemical treatment unit 2; the evaporation crystallization unit 4 includes an evaporation crystallization device 40 and a mother liquor treatment device 41; the evaporation crystallization device 40 is configured to perform evaporation crystallization on the effluent from the membrane concentration unit 3 to obtain evaporation crystallization mother liquor; the mother liquor treatment device 41 is configured to treat the evaporation crystallization mother liquor. The mother liquor undergoes mother liquor pretreatment to obtain evaporation crystallization mother liquor driving liquid; the forward osmosis concentration unit 5 has an inlet 50, a liquid inlet 51, an outlet 52, and a liquid outlet 53. The inlet 50 is connected to the organic wastewater pretreatment unit 1 to receive the filtered organic wastewater, and the liquid inlet 51 is connected to the liquid outlet of the mother liquor treatment device 41 to receive the evaporation crystallization mother liquor driving liquid; the forward osmosis concentration unit 5 is configured to concentrate the filtered organic wastewater and dilute the evaporation crystallization mother liquor driving liquid, the outlet 52 is used to discharge the concentrated organic wastewater, and the outlet 53 is used to discharge the diluted evaporation crystallization mother liquor driving liquid.

[0039] Therefore, the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided in this embodiment filters organic wastewater through the organic wastewater pretreatment unit 1, removing impurities and laying the foundation for the concentration of organic wastewater by the forward osmosis concentration unit 5; it treats wastewater through the biochemical treatment unit 2 and the membrane concentration unit 3, laying the foundation for obtaining evaporation crystallization mother liquor; it performs evaporation crystallization treatment on the membrane concentrate using the evaporation crystallization device 40, obtaining evaporation crystallization mother liquor, thus laying the foundation for obtaining the driving fluid required by the forward osmosis concentration unit 5; and it processes the evaporation crystallization mother liquor using the mother liquor treatment device 41. The mother liquor undergoes pretreatment to remove organic matter, hardness, and suspended solids, thus obtaining the driving fluid required for the forward osmosis concentration unit 5. This lays the foundation for the concentration of organic wastewater by the forward osmosis concentration unit 5 and allows for the rational utilization of the mother liquor, thereby reducing the disposal cost of the mother liquor. Compared with other membrane concentration processes, the forward osmosis membrane exhibits relatively less fouling when concentrating organic wastewater through the forward osmosis concentration unit 5. Furthermore, the concentrated organic wastewater after forward osmosis treatment has a high organic matter concentration and a small volume, which can effectively reduce environmental pollution and energy consumption.

[0040] Specifically, on the one hand, the effluent from the organic wastewater pretreatment unit 1 is transported from the inlet 50 of the forward osmosis concentration unit 5 to the forward osmosis raw water tank of the forward osmosis concentration unit 5 for later use. On the other hand, the wastewater is first treated by the equalization tank (not shown in the figure) and then flows into the biological treatment unit 2 for biological treatment; then the wastewater after biological treatment is subjected to coagulation and sedimentation, and the effluent after coagulation and sedimentation flows into the membrane concentration unit 3 for membrane concentration treatment; then the effluent from the membrane concentration unit 3 is transported to the evaporation crystallization equipment 40 for evaporation crystallization treatment; then the evaporation crystallization mother liquor obtained after evaporation crystallization treatment is transported to the mother liquor treatment equipment 41 to obtain the evaporation crystallization mother liquor driving liquid; finally, the evaporation crystallization mother liquor driving liquid is transported from the inlet 51 of the forward osmosis concentration unit 5 to the forward osmosis driving liquid tank of the forward osmosis concentration unit 5 for later use. Organic wastewater in the forward osmosis raw water tank is pumped into the feed liquid side of the forward osmosis membrane module of the forward osmosis concentration unit 5 via the forward osmosis raw water pump and circulates. At the same time, the evaporation crystallization mother liquor driving liquid in the forward osmosis driving liquid tank is pumped into the driving liquid side of the forward osmosis membrane module via the forward osmosis driving liquid pump and circulates. Water in the organic wastewater enters the evaporation crystallization mother liquor driving liquid on the forward osmosis driving liquid side through the forward osmosis membrane module. As the evaporation crystallization mother liquor driving liquid continuously dilutes the wastewater, the organic wastewater is gradually concentrated. Finally, the concentrated organic wastewater can be discharged through the outlet 52 of the forward osmosis concentration unit 5, and the diluted evaporation crystallization mother liquor driving liquid can be discharged through the outlet 53 of the forward osmosis concentration unit 5.

[0041] It should be noted that the wastewater supplied to the biochemical treatment unit 2 includes, but is not limited to, coking wastewater and cold rolling wastewater, as long as the wastewater, after being treated by the biochemical treatment unit 2, membrane concentration unit 3, and evaporation crystallization unit 4, can be used as the driving fluid for the forward osmosis concentration unit 5. Furthermore, the present invention does not limit the organic wastewater; for example, the organic wastewater can be, but is not limited to, beer wastewater.

[0042] Furthermore, the evaporation crystallization equipment 40 includes, but is not limited to, an MVR evaporation crystallization equipment. Thus, after MVR evaporation crystallization treatment using the MVR evaporation crystallization equipment, an evaporation crystallization mother liquor can be obtained.

[0043] Preferably, the organic wastewater pretreatment unit 1 includes a screen 10, a hydraulic screen 11, and a primary sedimentation tank 12 arranged in sequence. Thus, after the organic wastewater is treated by the screen 10, the hydraulic screen 11, and the primary sedimentation tank 12, impurities in the organic wastewater can be filtered out, laying the foundation for the subsequent concentration treatment of the organic wastewater by the forward osmosis concentration unit 5.

[0044] Specifically, the organic wastewater first passes through a mechanical screen 10 to remove large particulate impurities before entering a collection well (not shown in the figure). Then, it is lifted by a collection well lift pump to a hydraulic screen 11 to remove small particulate impurities before entering a primary sedimentation tank 12. Finally, the effluent after sedimentation treatment in the primary sedimentation tank 12 is transported from the inlet 50 of the forward osmosis concentration unit 5 to the forward osmosis raw water tank of the forward osmosis concentration unit 5 for later use.

[0045] Furthermore, the biochemical treatment unit 2 includes a primary anoxic tank 20, a primary aerobic tank 21, a secondary anoxic tank 22, and a secondary aerobic tank 23 arranged sequentially. The secondary anoxic tank 22 is connected to the outlet 52. Thus, by setting up the biochemical treatment unit 2, which includes the primary anoxic tank 20, the primary aerobic tank 21, the secondary anoxic tank 22, and the secondary aerobic tank 23, biological denitrification and removal of organic pollutants from wastewater can be achieved. The secondary anoxic tank 22, as a post-denitrification tank, requires periodic addition of carbon source. By connecting the outlet 52 of the forward osmosis concentration unit 5 to the secondary anoxic tank 22 of the biochemical treatment unit 2, the concentrated organic wastewater can be reused as a carbon source in the biochemical treatment unit 2. Moreover, the concentrated organic wastewater after forward osmosis treatment has a high organic matter concentration and small volume, which reduces the impact on the biochemical treatment unit 2 and lowers transportation costs. This enables the resource utilization of organic wastewater, forming a circular concentration system for organic wastewater, which has a synergistic effect of pollution reduction and carbon reduction and extremely important environmental protection significance.

[0046] It should be noted that, as those skilled in the art will understand, the present invention does not impose excessive limitations on the process sections set in the biochemical treatment unit 2, and can be set according to the type of wastewater. Furthermore, when the biochemical treatment unit 2 does not require a carbon source, the outlet 52 of the forward osmosis concentration unit 5 does not need to be connected to the biochemical treatment unit 2; the concentrated organic wastewater can be directly discharged and collected from the outlet 52. When certain process sections in the biochemical treatment unit 2 require a carbon source, the concentrated organic wastewater can first be discharged from the outlet 52 to the carbon source collection tank of the biochemical treatment unit 2 (not shown in the figure), and then added as a carbon source to the process sections requiring a carbon source.

[0047] Preferably, the outlet 53 of the forward osmosis concentration unit 5 is connected to the membrane concentration unit 3. Therefore, by connecting the outlet 53 of the forward osmosis concentration unit 5 to the membrane concentration unit 3, the diluted solution of the evaporation crystallization mother liquor driving liquid generated by the forward osmosis concentration unit 5 can be reused in the membrane concentration unit 3, thereby reducing the disposal costs of the diluted solution of the evaporation crystallization mother liquor driving liquid.

[0048] Furthermore, the outlet 53 is equipped with a control valve (not shown in the figure), which is configured to control the diluent to be discharged to the membrane concentration unit 3 when the ratio of the salt content of the evaporated crystallization mother liquor to the salt content of the diluent reaches a preset range.

[0049] For example, in some exemplary embodiments, the preset range can be 0.2 to 0.5. This ensures the concentration effect of the forward osmosis concentration unit 5.

[0050] Preferably, the membrane concentration unit 3 includes a reverse osmosis unit 30, a nanofiltration desalination unit 31, a high-pressure reverse osmosis unit 32, and an electrodialysis unit 33 connected in sequence, with the outlet 53 connected to the nanofiltration desalination unit 31. Thus, by connecting the outlet 53 of the forward osmosis concentration unit 5 to the nanofiltration desalination unit 31 of the membrane concentration unit 3, the diluted liquid from the evaporation crystallization mother liquor driving liquid can be returned to the nanofiltration desalination unit 31 of the membrane concentration unit 3 for re-desalination and concentration.

[0051] It should be noted that the present invention does not impose excessive limitations on the membrane concentration device provided in the membrane concentration unit 3, and the device can be configured according to the specific wastewater treatment situation. For example, in other embodiments, the membrane concentration unit 3 may include a reverse osmosis device 30, a high-pressure reverse osmosis device 32, and an electrodialysis device 33 connected in sequence, and the outlet 53 may be connected to the reverse osmosis device 30.

[0052] Preferably, the mother liquor treatment equipment 41 includes an advanced oxidation device 410, a chemical precipitation device 411, and a filtration device 412 arranged sequentially. Thus, by pretreating the evaporated crystallization mother liquor through the advanced oxidation device 410, the chemical precipitation device 411, and the filtration device 412, organic matter, hardness, and suspended solids in the evaporated crystallization mother liquor can be removed, thereby obtaining the driving fluid required by the forward osmosis concentration unit 5. This driving fluid is transported from the inlet 51 of the forward osmosis concentration unit 5 to the forward osmosis driving fluid tank of the forward osmosis concentration unit 5 for later use, laying the foundation for the concentration of organic wastewater by the forward osmosis concentration unit 5.

[0053] Specifically, the advanced oxidation device 410 includes, but is not limited to, an ozone catalytic oxidation device, an electrocatalytic oxidation device, and a wet catalytic oxidation device, used to remove high concentrations of organic matter from the evaporation crystallization mother liquor; the chemical precipitation device 411 removes the hardness of the evaporation crystallization mother liquor by adding sodium hydroxide and polyacrylamide and by clarifying and precipitating through a high-efficiency sedimentation tank; the filtration device 412 includes, but is not limited to, a multi-media filter and an ultrafiltration membrane, used to remove turbidity and suspended solids from the evaporation crystallization mother liquor.

[0054] To better understand the present invention, the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided in this embodiment will be used, exemplarily, when the wastewater supplied to the biochemical treatment unit 2 is coking wastewater and the organic wastewater is beer wastewater.

[0055] First, the coking wastewater enters the equalization tank for water quality adjustment, and then flows into the biological treatment unit 2 for biological denitrification and removal of organic pollutants. The biological treatment unit 2 includes a primary anoxic tank 20, a primary aerobic tank 21, a secondary anoxic tank 22, and a secondary aerobic tank 23 arranged sequentially. The secondary anoxic tank 22 serves as a post-denitrification tank and requires periodic addition of carbon source. The coking wastewater after biological treatment undergoes coagulation and sedimentation. The effluent after coagulation and sedimentation is then deeply reused through the membrane concentration unit 3. The membrane concentration unit 3 includes a reverse osmosis device 30, a nanofiltration desalination device 31, a high-pressure reverse osmosis device 32, and an electrodialysis device 33 connected in sequence. The high-concentration brine formed by the membrane concentration unit 3 is treated by MVR evaporation and crystallization to form sodium chloride industrial salt and evaporation crystallization mother liquor. The salt content of the evaporation crystallization mother liquor is 20.5% to 27.5%.

[0056] Then, the evaporation crystallization mother liquor is transported to the mother liquor treatment equipment 41, and pretreated sequentially through an advanced oxidation device 410, a chemical precipitation device 411, and a filtration device 412. The advanced oxidation device 410 includes, but is not limited to, an ozone catalytic oxidation device, an electrocatalytic oxidation device, and a wet catalytic oxidation device, used to remove high-concentration organic matter from the evaporation crystallization mother liquor. The organic matter concentration of the effluent obtained after treatment by the advanced oxidation device 410 is less than 30 mg / L. The chemical precipitation device 411 is used to remove the hardness of the evaporation crystallization mother liquor. After adding 5% to 8% sodium hydroxide and 1 mg / L to 5 mg / L polyacrylamide to the effluent obtained after treatment by the advanced oxidation device 410, the effluent is clarified and precipitated in a high-efficiency sedimentation tank. The suspended solids concentration in the effluent of the high-efficiency sedimentation tank is less than 15 mg / L. The filtration device 412 is used to remove the turbidity and suspended solids of the evaporation crystallization mother liquor, using a multi-media filter and an ultrafiltration membrane. The suspended solids concentration in the effluent obtained after treatment by the filtration device 412 is less than 1 mg / L. The evaporated and crystallized mother liquor, after pretreatment, is pumped into the forward osmosis drive liquid tank of the forward osmosis concentration unit 5 for later use.

[0057] Next, the beer wastewater is transported to the organic wastewater pretreatment unit 1, where the COD concentration is 2000 mg / L to 3000 mg / L. After large particulate impurities are removed by the mechanical screen 10, the wastewater enters the collection well and is then pumped by the collection well lift pump to the hydraulic screen 11 to remove small particulate impurities before entering the primary sedimentation tank 12 for sedimentation treatment. The effluent after sedimentation treatment is then transported to the forward osmosis raw water tank of the forward osmosis concentration unit 5 through the inlet 50.

[0058] Finally, the beer wastewater from the forward osmosis raw water tank is pumped into the feed liquid side of the forward osmosis membrane module of the forward osmosis concentration unit 5 via the forward osmosis raw water pump for circulation. Simultaneously, the evaporation crystallization mother liquor driving liquid from the forward osmosis driving liquid tank is pumped into the driving liquid side of the forward osmosis membrane module for circulation. Water from the beer wastewater passes through the forward osmosis membrane module and enters the evaporation crystallization mother liquor driving liquid on the forward osmosis driving liquid side. As the evaporation crystallization mother liquor driving liquid continuously dilutes the wastewater, it gradually concentrates. When the evaporation crystallization mother liquor driving liquid in the forward osmosis driving liquid tank is diluted to an initial salt content of 0.2 to 0.5, the control valve of the outlet 53 of the forward osmosis concentration unit 5 is opened, and the diluted solution is discharged to the nanofiltration salt separation device 31 of the membrane concentration unit 3 for re-salt separation and concentration. The COD concentration of the concentrated beer wastewater from the forward osmosis raw water tank is 4000 mg / L to 12000 mg / L. This concentrated solution is pumped into the carbon source collection tank and periodically added to the secondary anoxic tank 22 as a carbon source.

[0059] Example 2

[0060] This embodiment provides a wastewater concentration method coupled with forward osmosis and evaporation crystallization. This wastewater concentration method is used in the wastewater concentration system coupled with forward osmosis and evaporation crystallization described in any of the above embodiments. Specifically, please refer to... Figure 3 , Figure 3 This is a schematic flow diagram of the wastewater concentration method coupled with forward osmosis and evaporation crystallization provided in this embodiment. From Figure 3 It can be seen that the wastewater concentration method includes:

[0061] S100: The organic wastewater is transported to the organic wastewater pretreatment unit 1 for filtration treatment, and the filtered organic wastewater is transported to the forward osmosis concentration unit 5 through the inlet 50 of the forward osmosis concentration unit 5.

[0062] S200: The wastewater is transported to the biochemical treatment unit 2 for biochemical treatment to obtain biochemical effluent;

[0063] S300: The biochemical effluent is transported to the membrane concentration unit 3 for membrane concentration treatment to obtain membrane concentrated water;

[0064] S400: The concentrated water from the membrane is transported to the evaporation crystallization equipment 40 for evaporation crystallization treatment to obtain evaporation crystallization mother liquor;

[0065] S500: The evaporation crystallization mother liquor is transported to the mother liquor treatment equipment 41 for mother liquor pretreatment to obtain evaporation crystallization mother liquor driving liquid, and the evaporation crystallization mother liquor driving liquid is transported to the forward osmosis concentration unit 5 through the liquid inlet 51 of the forward osmosis concentration unit 5.

[0066] S600: Concentrate the filtered organic wastewater and dilute the evaporation crystallization mother liquor driving liquid;

[0067] S700: Discharge the concentrated organic wastewater;

[0068] S800: Discharge the diluted solution of the evaporation crystallization mother liquor driving liquid.

[0069] Therefore, the wastewater concentration method provided in this embodiment can use the evaporation crystallization mother liquor obtained after being processed by the biochemical treatment unit 2, the membrane concentration unit 3 and the evaporation crystallization equipment 40, and then pre-treat the mother liquor by the mother liquor treatment equipment 41, as the driving liquid for the forward osmosis concentration unit 5 to concentrate organic wastewater. At the same time, it can reduce the disposal cost of the evaporation crystallization mother liquor and realize the resource utilization of the evaporation crystallization mother liquor.

[0070] Preferably, the wastewater concentration method further includes:

[0071] S710: Discharge the concentrated organic wastewater into the biochemical treatment unit 2;

[0072] S810: Discharge the diluted solution of the evaporation crystallization mother liquor driving liquid into the membrane concentration unit 3.

[0073] Therefore, by discharging the concentrated organic wastewater to the biochemical treatment unit 2, it can be recycled as a carbon source for the biochemical treatment unit 2. Moreover, the concentrated organic wastewater after forward osmosis treatment has a high organic matter concentration and small volume, which can reduce the impact on the biochemical treatment unit 2 and reduce transportation costs. This enables the resource utilization of organic wastewater and forms a circular concentration system for organic wastewater, which has a synergistic effect of pollution reduction and carbon reduction and extremely important environmental protection significance. By discharging the diluted liquid of the evaporation crystallization mother liquor driving liquid to the membrane concentration unit 3, the disposal cost of the diluted liquid of the evaporation crystallization mother liquor driving liquid can be reduced.

[0074] In summary, the wastewater concentration system and method coupled with forward osmosis and evaporative crystallization provided by this invention have the following advantages: The wastewater concentration system coupled with forward osmosis and evaporative crystallization provided by this invention includes: an organic wastewater pretreatment unit, a biochemical treatment unit, a membrane concentration unit, an evaporative crystallization unit, and a forward osmosis concentration unit; the organic wastewater pretreatment unit is used to filter organic wastewater; the biochemical treatment unit is used to perform biochemical treatment on wastewater; the membrane concentration unit is used to perform membrane concentration treatment on the biochemical effluent from the biochemical treatment unit; the evaporative crystallization unit includes an evaporative crystallization device and a mother liquor treatment device; the evaporative crystallization device is configured to perform evaporative crystallization treatment on the effluent from the membrane concentration unit to obtain... An evaporation crystallization mother liquor is obtained; the mother liquor treatment equipment is configured to pretreat the evaporation crystallization mother liquor to obtain an evaporation crystallization mother liquor driving liquid; the forward osmosis concentration unit has an inlet, a liquid inlet, an outlet, and a liquid outlet, the inlet is connected to the organic wastewater pretreatment unit to receive the filtered organic wastewater, the liquid inlet is connected to the liquid outlet of the mother liquor treatment equipment to receive the evaporation crystallization mother liquor driving liquid; the forward osmosis concentration unit is configured to concentrate the filtered organic wastewater and dilute the evaporation crystallization mother liquor driving liquid, the outlet is used to discharge the concentrated organic wastewater, and the liquid outlet is used to discharge the diluted evaporation crystallization mother liquor driving liquid. Therefore, the wastewater concentration system coupled with forward osmosis and evaporative crystallization provided by this invention filters organic wastewater through an organic wastewater pretreatment unit, removing impurities and laying the foundation for the concentration of organic wastewater in the forward osmosis concentration unit. It treats wastewater through a biochemical treatment unit and a membrane concentration unit, providing a basis for obtaining evaporative crystallization mother liquor. The evaporative crystallization equipment treats the concentrated membrane water to obtain evaporative crystallization mother liquor, providing a basis for obtaining the driving fluid required by the forward osmosis concentration unit. The mother liquor treatment equipment pretreats the evaporative crystallization mother liquor, removing organic matter, hardness, and suspended solids, thus obtaining the driving fluid required by the forward osmosis concentration unit, further laying the foundation for the concentration of organic wastewater in the forward osmosis concentration unit. Simultaneously, it allows for the rational utilization of the evaporative crystallization mother liquor, reducing its disposal costs. Compared with other membrane concentration processes, the forward osmosis membrane exhibits relatively less fouling when concentrating organic wastewater through the forward osmosis concentration unit. Furthermore, the concentrated organic wastewater after forward osmosis treatment has a high organic matter concentration and small volume, effectively reducing environmental pollution and energy consumption.

[0075] Furthermore, the biochemical treatment unit includes a primary anoxic tank, a primary aerobic tank, a secondary anoxic tank, and a secondary aerobic tank arranged sequentially, with the secondary anoxic tank connected to the effluent outlet. Thus, the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided by this invention, by setting up a biochemical treatment unit including a primary anoxic tank, a primary aerobic tank, a secondary anoxic tank, and a secondary aerobic tank, can perform biological denitrification and organic pollutant removal treatment on wastewater. The secondary anoxic tank, acting as a post-denitrification tank, requires periodic addition of a carbon source. By connecting the effluent outlet of the forward osmosis concentration unit to the secondary anoxic tank of the biochemical treatment unit, the concentrated organic wastewater can be reused as a carbon source in the biochemical treatment unit. Moreover, the concentrated organic wastewater after forward osmosis treatment has a high organic matter concentration and small volume, reducing the impact on the biochemical treatment unit and lowering transportation costs. This enables the resource utilization of organic wastewater, forming a circular concentration system for organic wastewater, which has a synergistic effect of pollution reduction and carbon reduction and extremely important environmental protection significance.

[0076] Furthermore, the outlet of the forward osmosis concentration unit is connected to the membrane concentration unit. Therefore, the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided by this invention, by connecting the outlet of the forward osmosis concentration unit to the membrane concentration unit, enables the dilution of the evaporation crystallization mother liquor driving liquid generated by the forward osmosis concentration unit to be reused in the membrane concentration unit, thereby reducing the disposal costs of the dilution of the evaporation crystallization mother liquor driving liquid.

[0077] Since the wastewater concentration method coupled with forward osmosis and evaporation crystallization provided by this invention belongs to the same inventive concept as the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided by this invention, the wastewater concentration method coupled with forward osmosis and evaporation crystallization provided by this invention has at least all the advantages of the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided by this invention. For the advantages of the wastewater concentration method coupled with forward osmosis and evaporation crystallization provided by this invention, please refer to the relevant description of the beneficial effects of the wastewater concentration system coupled with forward osmosis and evaporation crystallization provided by this invention, which will not be repeated here.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A forward osmosis and evaporative crystallization coupled wastewater concentration system, characterized in that, The wastewater concentration system comprises an organic wastewater pretreatment unit, a biochemical treatment unit, a membrane concentration unit, an evaporation crystallization unit and a forward osmosis concentration unit. The organic wastewater pretreatment unit is configured to filter the organic wastewater. The biochemical treatment unit is configured to perform biochemical treatment on the wastewater. The membrane concentration unit is configured to perform membrane concentration treatment on the biochemical effluent from the biochemical treatment unit. The evaporation crystallization unit comprises an evaporation crystallization device and a mother liquor treatment device; the evaporation crystallization device is configured to perform evaporation crystallization treatment on the effluent from the membrane concentration unit to obtain evaporation crystallization mother liquor; the mother liquor treatment device comprises a high-level oxidation device, a chemical precipitation device and a filter device arranged in sequence, and is configured to perform mother liquor pretreatment on the evaporation crystallization mother liquor to obtain evaporation crystallization mother liquor driving liquid. The forward osmosis concentration unit has a water inlet, a liquid inlet, a water outlet and a liquid outlet; the water inlet is in communication with the organic wastewater pretreatment unit to receive the filtered organic wastewater; the liquid inlet is in communication with the liquid outlet end of the mother liquor treatment device to receive the evaporation crystallization mother liquor driving liquid; the forward osmosis concentration unit is configured to concentrate the filtered organic wastewater and dilute the evaporation crystallization mother liquor driving liquid; the water outlet is configured to discharge the concentrated organic wastewater to the biochemical treatment unit; and the liquid outlet is configured to discharge the diluted evaporation crystallization mother liquor driving liquid, and the liquid outlet of the forward osmosis concentration unit is connected to the membrane concentration unit.

2. The forward osmosis and evaporative crystallization coupled wastewater concentration system of claim 1, wherein, The organic wastewater pretreatment unit comprises a grid, a hydraulic sieve and a primary sedimentation tank arranged in sequence.

3. The forward osmosis and evaporative crystallization coupled wastewater concentration system of claim 1, wherein, The biochemical treatment unit comprises a primary anoxic tank, a primary aerobic tank, a secondary anoxic tank and a secondary aerobic tank arranged in sequence, and the secondary anoxic tank is in communication with the water outlet.

4. The forward osmosis and evaporative crystallization coupled wastewater concentration system of claim 1, wherein, The liquid outlet is provided with a control valve configured to control the discharge of the diluted liquid to the membrane concentration unit when the ratio of the salt content of the evaporation crystallization mother liquor to the salt content of the diluted liquid reaches a preset range.

5. The forward osmosis and evaporative crystallization coupled wastewater concentration system of claim 4, wherein, The preset range is 0.2 to 0.

5.

6. The forward osmosis and evaporative crystallization coupled wastewater concentration system of claim 1, wherein, The membrane concentration unit comprises a reverse osmosis device, a nanofiltration salt separation device, a high-pressure reverse osmosis device and an electrodialysis device connected in sequence, and the liquid outlet is connected to the nanofiltration salt separation device.

7. A method for wastewater concentration by coupling forward osmosis with evaporative crystallization, characterized in that, The wastewater concentration method adopts the forward osmosis and evaporation crystallization coupled wastewater concentration system according to any one of claims 1 to 6, and the wastewater concentration method comprises: delivering the organic wastewater to the organic wastewater pretreatment unit for filtration treatment, and delivering the filtered organic wastewater to the forward osmosis concentration unit through the water inlet of the forward osmosis concentration unit; delivering the wastewater to the biochemical treatment unit for biochemical treatment to obtain biochemical effluent; delivering the biochemical effluent to the membrane concentration unit for membrane concentration treatment to obtain membrane concentration concentrated water; delivering the membrane concentration concentrated water to the evaporation crystallization device for evaporation crystallization treatment to obtain evaporation crystallization mother liquor; The evaporation crystallization mother liquor is delivered to the mother liquor treatment device for mother liquor pretreatment to obtain evaporation crystallization mother liquor driving liquid, and the evaporation crystallization mother liquor driving liquid is delivered to the forward osmosis concentration unit through the liquid inlet of the forward osmosis concentration unit; The filtered organic wastewater is concentrated and the evaporation crystallization mother liquor driving liquid is diluted; The concentrated liquid of the organic wastewater is discharged to the biochemical treatment unit; The diluted liquid of the evaporation crystallization mother liquor driving liquid is discharged to the membrane concentration unit.

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