A new type of membrane concentration system, its process and high-fold concentration device

Abstract

The present invention discloses a novel membrane concentration system, which includes a pretreatment device, a reverse osmosis device, a high-fold concentration device, an ion exchange device, and an advanced oxidation device; it can achieve high-fold concentration; the operating pressure is low, greatly reducing the operating energy consumption of the system. The present invention also discloses a novel membrane concentration process, which fully utilizes the characteristics of the reverse osmosis membrane. By returning a part of the concentrated water of the next-stage weak reverse osmosis membrane to the water production side of the previous-stage weak reverse osmosis membrane, the inorganic salt content on the water production side of the previous-stage weak reverse osmosis membrane is increased, and the osmotic pressure difference between the concentrated water side and the water production side of the weak reverse osmosis membrane is reduced. Furthermore, under a lower operating pressure, high-fold concentration is achieved. The present invention also discloses a high-fold concentration device, which gradually increases the inorganic salt content in the concentrated water through multiple stages of weak reverse osmosis membranes; by providing a reflux inlet on the water production side of each previous-stage weak reverse osmosis membrane, part of the concentrated water is refluxed, and finally high-fold concentration is achieved.

Description

Technical Field:

[0001] The present invention relates to the field of wastewater treatment, and particularly to a novel membrane concentration system, its process, and a high-fold concentration device. Background Art:

[0002] During the production processes of coal chemical industry, electronic products, and other industries, a large amount of wastewater is generated. Its main characteristics are that it contains inorganic salt ions, suspended solids, polluting impurity ions, organic substances, etc., and the contents of various substances vary greatly. The inorganic salt content is between 5000 mg / L and 15000 mg / L; the suspended solid content is between 30 mg / L and 500 mg / L; the polluting impurity ions are mainly scale-forming substances such as calcium ions, magnesium ions, and silicon dioxide, with contents ranging from dozens to hundreds of mg / L, and even up to thousands of mg / L; organic substances are the most difficult to remove among the pollutants, and their contents also vary from dozens to hundreds of mg / L, resulting in large fluctuations in the quality and quantity of industrial wastewater, complex composition, and difficulties in membrane concentration and resource recovery and utilization.

[0003] To realize the recycling of water resources in wastewater, membrane concentration technology is usually adopted to recycle all the water in the wastewater. However, restricted by the current development level of membrane technology at home and abroad, the traditional membrane concentration technology has the limitation that the concentration multiple of a single membrane concentration device is limited. For example, a conventional brackish water membrane can only be concentrated to 25000 - 30000 mg / L, a seawater desalination membrane can be concentrated to 55000 - 60000 mg / L, a high-pressure reverse osmosis membrane can be concentrated to 90000 - 100000 mg / L, and a high-pressure flat membrane can be concentrated to 110000 - 120000 mg / L. Moreover, the concentration of the membrane system mainly realizes the high-fold concentration of inorganic salts in the wastewater by increasing the operating pressure, that is, by operating multiple membrane systems in series under high-pressure conditions. The problems it has are large operating pressure, high investment cost, and poor operating stability.

[0004] Some scholars have tried to directly concentrate wastewater to 100,000 mg / L - 120,000 mg / L using high-pressure flat membranes to shorten the process flow. However, a large amount of low-concentration wastewater directly enters the high-pressure flat membranes, resulting in a large treatment load and high energy consumption of the high-pressure flat membranes, seriously affecting the economy of the membrane concentration system. Moreover, the water quality of the produced water by the high-pressure flat membranes is not good and needs further treatment, further increasing the complexity of the system. In addition, affected by the performance of the membrane technology itself, traditional membrane technology can only concentrate inorganic salt ions in water to 100,000 mg / L - 120,000 mg / L. If the concentration multiple needs to be further increased, an evaporation system needs to be used, resulting in high energy consumption. For example, to evaporate 1 kg of water, 0.45 kg of steam or 2 - 4 kWh of electricity is required, greatly affecting the economic benefits of enterprises. Therefore, developing a new type of membrane concentration technology that can directly concentrate inorganic salts in wastewater at a high multiple under lower operating pressure conditions, avoiding problems such as long process flow, poor stability, and high energy consumption caused by the series operation of traditional multiple membranes, will be an important way to solve the current industrial wastewater treatment problem. Summary of the Invention:

[0005] The first object of the present invention is to provide a new type of membrane concentration system with low energy consumption and stable operation.

[0006] The second object of the present invention is to provide a new type of membrane concentration process with low osmotic pressure difference and high concentration multiple.

[0007] The third object of the present invention is to provide a high-concentration device with simple structure and good concentration effect.

[0008] The first object of the present invention is implemented by the following technical solutions:

[0009] A new type of membrane concentration system includes a pretreatment device, a reverse osmosis device, and a high-concentration device;

[0010] The concentrated water outlet of the submerged ultrafiltration membrane of the pretreatment device is communicated with the water inlet of the reverse osmosis device. The concentrated water outlet of the reverse osmosis device is communicated with the water inlet of the first-stage weak reverse osmosis membrane of the high-concentration device. The concentrated water outlet of the last-stage weak reverse osmosis membrane of the high-concentration device is communicated with the water inlet of the concentrated water tank. The produced water outlet of the reverse osmosis device is communicated with the water inlet of the reused water tank. The produced water outlets of the multiple weak reverse osmosis membranes of the high-concentration device are all communicated with the water inlet of the reverse osmosis device.

[0011] Further, the high-concentration device includes multiple stages of weak reverse osmosis membranes, and a reflux water inlet is provided on the produced water side of each upper-stage weak reverse osmosis membrane;

[0012] The concentrated water outlet of the next-stage weak reverse osmosis membrane is divided into two paths. One path is connected to the water inlet of the next-next-stage weak reverse osmosis membrane, and the other path is connected to the reflux water inlet on the water production side of the previous-stage weak reverse osmosis membrane.

[0013] Furthermore, the number of the weak reverse osmosis membranes is 4 to 8.

[0014] Furthermore, it further includes an ion exchange device and an advanced oxidation device;

[0015] The concentrated water outlet of the reverse osmosis device is connected to the water inlet of the ion exchange device, the water outlet of the ion exchange device is connected to the water inlet of the advanced oxidation device, and the water outlet of the advanced oxidation device is connected to the water inlet of the first-stage weak reverse osmosis membrane of the high-fold concentration device.

[0016] Furthermore, the pretreatment device includes a high-density sedimentation tank, a quartz sand filter, and a submerged ultrafiltration membrane;

[0017] The water outlet of the high-density sedimentation tank is connected to the water inlet of the quartz sand filter, and the water production outlet of the quartz sand filter is connected to the water inlet of the submerged ultrafiltration membrane.

[0018] The second object of the present invention is implemented by the following technical solutions:

[0019] A new membrane concentration process includes the following processes: Process 1: Pretreatment; Process 2: Preliminary concentration; Process 3: High-fold concentration; where:

[0020] Process 1: Pretreatment: Wastewater enters the pretreatment device to remove calcium ions, magnesium ions, silicon dioxide, suspended solids, turbidity, etc. in the wastewater to obtain pretreatment produced water, and the calcium ion concentration in the pretreatment produced water < 40 mg / L, the magnesium ion concentration < 20 mg / L, the suspended solid content < 0.1 mg / L, and the turbidity < 3 NTU;

[0021] Process 2: Preliminary concentration: The pretreatment produced water obtained in Process 1 of pretreatment is sent into the reverse osmosis device for preliminary concentration to obtain reverse osmosis concentrated water and reverse osmosis produced water, and the content of inorganic salts in the reverse osmosis concentrated water is concentrated to 30000 mg / L to 35000 mg / L; the reverse osmosis produced water is sent into the reused water tank for storage and standby;

[0022] Process 3: High-fold concentration: The reverse osmosis concentrated water obtained in Process 2 of preliminary concentration is sent into the high-fold concentration device for high-fold concentration to obtain high-fold concentration concentrated water and high-fold concentration produced water, and the content of inorganic salts in the high-fold concentration concentrated water is concentrated to more than 180000 mg / L. The high-fold concentration concentrated water is sent into the concentrated water tank for storage and standby, and the high-fold concentration produced water returns to Process 2 of preliminary concentration to participate in the concentration treatment again.

[0023] Further, in the high - multiple concentration of Process 3, the reverse osmosis concentrated water obtained in the preliminary concentration of Process 2 is sequentially fed into multiple - stage weak reverse osmosis membranes for step - by - step concentration, and a part of the concentrated water of the next - stage weak reverse osmosis membrane is returned to the water production side of the previous - stage weak reverse osmosis membrane.

[0024] Further, it further includes Process 4 hard - removal treatment and Process 5 oxidation treatment; where

[0025] Process 4 hard - removal treatment: The reverse osmosis concentrated water obtained in the preliminary concentration of Process 2 is fed into the ion - exchange device to remove calcium ions and magnesium ions in the wastewater, obtaining hard - removal produced water, and the total concentration of scale - forming ions in the hard - removal produced water < 5 mg / L;

[0026] Process 5 oxidation treatment: The hard - removal produced water obtained in Process 4 hard - removal treatment is fed into the advanced oxidation device for oxidation treatment to remove organic substances, obtaining oxidation produced water, and the organic substance concentration in the oxidation produced water < 300 mg / L. The oxidation produced water is fed into the high - multiple concentration of Process 3 and is subjected to step - by - step concentration treatment through the high - multiple concentration device.

[0027] Further, in the pretreatment of Process 1, the wastewater first enters the high - density sedimentation tank to remove substances such as calcium ions, magnesium ions, silicon dioxide, and suspended solids in the wastewater; then, it enters the quartz sand filter to remove the suspended solids in the wastewater; after that, it enters the submerged ultrafiltration membrane to further remove turbidity and suspended solids.

[0028] The third object of the present invention is implemented by the following technical solution:

[0029] A high - multiple concentration device, including multiple - stage weak reverse osmosis membranes, and a reflux water inlet is provided on the water production side of each previous - stage weak reverse osmosis membrane;

[0030] The concentrated water outlet of the next - stage weak reverse osmosis membrane is divided into two paths. One path is communicated with the water inlet of the next - but - one - stage weak reverse osmosis membrane, and the other path is communicated with the reflux water inlet on the water production side of the previous - stage weak reverse osmosis membrane.

[0031] Advantages of the present invention:

[0032] The system of the present invention can concentrate the inorganic salts in wastewater to more than 180,000 mg / L. Compared with the traditional series system of multiple membranes that can only concentrate to 120,000 mg / L, the concentration multiple is more than 1.5 times that of the traditional one. Moreover, there is no need to use a thermal evaporation concentration device, avoiding the high investment and high operating costs caused by high-temperature evaporation equipment. Compared with the traditional treatment system, the investment cost is reduced by about 30%. The maximum operating pressure involved in this system is 7 MPa, and the operating pressure is low, avoiding problems such as poor operating stability and high energy consumption caused by the membrane system under high pressure. Under the condition of the same concentration multiple, compared with the traditional treatment system, it can save about 70% of the energy consumption, greatly reducing the operating energy consumption of the system.

[0033] In the process of the present invention, the characteristics of the reverse osmosis membrane are fully utilized. During the high-fold concentration treatment process, by returning 20% - 50% of the total amount of concentrated water of the next-stage weak reverse osmosis membrane to the water production side of the previous-stage weak reverse osmosis membrane, the content of inorganic salts on the water production side of the previous-stage weak reverse osmosis membrane is increased, so that under a lower operating pressure, the content of inorganic salts in the concentrated water side of the corresponding weak reverse osmosis membrane is increased, and then high-fold concentration is achieved under a low osmotic pressure difference. At the same time, since inorganic salt ions and other impurity ions are retained on the concentrated water side of the reverse osmosis, by cooperating with the hardness removal treatment and oxidation treatment to remove scale-forming ions such as calcium and magnesium and organic substances in the wastewater, the long-term stable operation of the system can be ensured. Returning the high-fold concentrated water to the previous process and participating in the concentration treatment again can maximize the recovery of salt ions and also achieve the full recovery of water resources.

[0034] In the high-fold concentration device of the present invention, the content of inorganic salts in the concentrated water is gradually increased through multiple stages of weak reverse osmosis membranes. By opening a reflux water inlet on the side wall of the water production side of each previous-stage weak reverse osmosis membrane, part of the concentrated water of the next-stage weak reverse osmosis membrane is refluxed to the water production side of the previous-stage weak reverse osmosis membrane, so that under a lower operating pressure, the content of inorganic salts in the concentrated water side of the corresponding weak reverse osmosis membrane is increased, and then high-fold concentration is achieved. BRIEF DESCRIPTION OF THE DRAWINGS:

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0036] Figure 1 It is a schematic diagram of the system connection of Embodiment 1.

[0037] Figure 2 It is a schematic diagram of Embodiment 4.

[0038] In the figure: pretreatment device 1, high-density sedimentation tank 11, quartz sand filter 12, submerged ultrafiltration membrane 13, reverse osmosis device 2, high-concentration device 3, weak reverse osmosis membrane 31, recycled water tank 4, ion exchange device 5, advanced oxidation device 6, concentrated water tank 7. Specific implementation method:

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Embodiment 1:

[0041] like Figure 1 A novel membrane concentration system shown includes a pretreatment device 1, a reverse osmosis device 2 and a high-concentration device 3; the pretreatment device 1 includes a high-density sedimentation tank 11, a quartz sand filter 12 and an immersed ultrafiltration membrane 13; the high-concentration device 3 includes 4-stage weak reverse osmosis membranes 31, and a reflux water inlet is opened on the water production side of each upper-stage weak reverse osmosis membrane 31; the concentrated water outlet of the lower-stage weak reverse osmosis membrane 31 is divided into two paths, one of which is connected to the water inlet of the next-stage weak reverse osmosis membrane 31, and the other is connected to the reflux water inlet on the water production side of the upper-stage weak reverse osmosis membrane 31. The weak reverse osmosis membrane 31 adopts 8040-weak reverse osmosis membrane produced by Toyobo Co., Ltd. This embodiment also includes an ion exchange device 5 and an advanced oxidation device 6; in this embodiment, the ion exchange resin of the ion exchange device 5 adopts a weak acid cation resin produced by Zhengguang Resin Co., Ltd.

[0042] The outlet of the high-density sedimentation tank 11 is connected to the inlet of the quartz sand filter 12, and the water outlet of the quartz sand filter 12 is connected to the inlet of the submerged ultrafiltration membrane 13; the concentrated water outlet of the submerged ultrafiltration membrane 13 is connected to the inlet of the reverse osmosis device 2, the concentrated water outlet of the reverse osmosis device 2 is connected to the inlet of the ion exchange device 5, the outlet of the ion exchange device 5 is connected to the inlet of the advanced oxidation device 6, the outlet of the advanced oxidation device 6 is connected to the inlet of the first-stage weak reverse osmosis membrane 31, and the concentrated water outlet of the last-stage weak reverse osmosis membrane 31 is connected to the inlet of the concentrated water tank 7. The water outlet of each weak reverse osmosis membrane 31 is connected to the inlet of the reverse osmosis device 2.

[0043] The water outlet of the reverse osmosis device 2 is connected to the water inlet of the recycled water tank 4 .

[0044] Working principle:

[0045] The wastewater first enters the high-density sedimentation tank 11. By adding chemicals such as sodium carbonate, sodium hydroxide, hydrochloric acid, PAM, and PFS into the high-density sedimentation tank 11, substances such as calcium ions, magnesium ions, silicon dioxide, and suspended solids in the wastewater are removed. Specifically, the ratio of the dosage of sodium carbonate to the total amount of calcium ions in the wastewater is (2.65 - 3):1; the dosage of sodium hydroxide is 1.1 - 1.15 times the sum of the total amount of heavy metal ions, the total amount of magnesium ions in the wastewater, and the total amount of sodium hydroxide required to adjust the pH; the dosage of hydrochloric acid is (the sum of the molar mass equivalent of the wastewater alkalinity and the molar mass equivalent of hydrochloric acid required to adjust the pH) divided by the industrial hydrochloric acid concentration and then multiplied by 1 - 1.15; the dosage of PAM is 3 - 5 mg / L, and the dosage of PFS is 100 - 150 mg / L.

[0046] The water produced by the high-density sedimentation tank 11 then passes through the quartz sand filter 12 to remove the suspended solids in the wastewater. After that, it passes through the submerged ultrafiltration membrane 13 to further remove turbidity and suspended solids, thus completing the pretreatment of the wastewater. After pretreatment, the calcium ion concentration in the wastewater is < 40 mg / L, the magnesium ion concentration is < 20 mg / L, the suspended solid content is < 0.1 mg / L, and the turbidity is < 3 NTU. Then, the pretreated water enters the reverse osmosis device 2 for concentration. After being concentrated by the reverse osmosis device 2, the content of inorganic salts in the concentrated water of the reverse osmosis device 2 is concentrated to 30000 mg / L - 35000 mg / L, and the produced water enters the reused water tank 4 as reused water for the water system in the factory area, which can improve the utilization rate of water resources; the concentrated water enters the ion exchange device 5, and the sodium ions on the ion exchange resin exchange and adsorb to remove the calcium ions and magnesium ions in the wastewater, ensuring that the scale-forming ions in the overall treatment process are always below 5 mg / L. The water produced by the ion exchange device 5 enters the advanced oxidation device 6. Using the strong oxidizing property of the hydroxyl radicals in the advanced oxidation device 6, the organic matter in the wastewater is removed, keeping the organic matter content in the wastewater below 300 mg / L, and then enters the high-fold concentration device 3 for further concentration; the content of inorganic salts in the concentrated water of the high-fold concentration device 3 is concentrated to more than 180000 mg / L, and then enters the concentrated water tank 7 for storage and standby; since the produced water of the high-fold concentration device 3 still contains salt ions, the produced water of the high-fold concentration device 3 is returned to the reverse osmosis device 2 for re-concentration treatment, so as to maximize the recovery of salt ions in the produced water.

[0047] In this embodiment, the high-concentration device 3 includes four-stage weak reverse osmosis membranes 31. The water produced by the advanced oxidation device 6 first enters the first-stage weak reverse osmosis membrane 31 for concentration. After concentration, the content of inorganic salts in the concentrated water produced by the first-stage weak reverse osmosis membrane 31 is concentrated to 50,000 - 60,000 mg / L. Then, the concentrated water enters the second-stage weak reverse osmosis membrane 31 for further concentration, so that the content of inorganic salts in the concentrated water produced by the second-stage weak reverse osmosis membrane 31 is concentrated to 80,000 - 90,000 mg / L. Then, the concentrated water enters the third-stage weak reverse osmosis membrane 31 for further concentration, so that the content of inorganic salts in the concentrated water produced by the third-stage weak reverse osmosis membrane 31 is concentrated to 130,000 - 140,000 mg / L. Finally, the concentrated water enters the fourth-stage weak reverse osmosis membrane 31 for further concentration, so that the content of inorganic salts in the concentrated water produced by the fourth-stage weak reverse osmosis membrane 31 is concentrated to 180,000 - 200,000 mg / L.

[0048] In this embodiment, by opening a reflux inlet on the water production side of the weak reverse osmosis membrane 31, 20% - 50% of the concentrated water of the next-stage weak reverse osmosis membrane 31 is refluxed to the water production side of the previous-stage weak reverse osmosis membrane 31. By increasing the content of inorganic salts on the water production side of the previous-stage weak reverse osmosis membrane 31, the content of inorganic salts in the concentrated water side of the corresponding weak reverse osmosis membrane 31 is increased under a relatively low operating pressure (7 MPa). Thus, high-fold concentration is achieved under a low osmotic pressure difference. Through the setting of multiple-stage weak reverse osmosis membranes 31, the content of inorganic salts in the finally obtained concentrated water reaches more than 1.5 times that of the traditional concentration system. Compared with the traditional system that uses an evaporation system to provide the concentration multiple, under the condition of reaching the same concentration multiple, about 70% of energy consumption can be saved, and the effect of energy conservation and consumption reduction is remarkable.

[0049] Example 2:

[0050] The process of treating wastewater using the novel membrane concentration system of Example 1 includes the following processes: Process 1, pretreatment; Process 2, preliminary concentration; Process 3, high-concentration; and also includes Process 4, hardness removal treatment and Process 5, oxidation treatment; where:

[0051] Process 1 - Pretreatment: The wastewater enters the pretreatment device 1. Specifically, the wastewater first enters the high - density sedimentation tank 11. By adding chemicals such as sodium carbonate, sodium hydroxide, hydrochloric acid, PAM, and PFS into the high - density sedimentation tank 11, substances such as calcium ions, magnesium ions, silicon dioxide, and suspended solids in the wastewater are removed. Moreover, the ratio of the dosage of sodium carbonate to the total amount of calcium ions in the wastewater is (2.65 - 3):1, the dosage of sodium hydroxide is 1.1 - 1.15 times the sum of the total amount of heavy metal ions, the total amount of magnesium ions in the wastewater and the total amount of sodium hydroxide required to adjust the pH; the dosage of hydrochloric acid is (the sum of the molar mass equivalent of the wastewater alkalinity and the molar mass equivalent of hydrochloric acid required to adjust the pH) divided by the industrial hydrochloric acid concentration and then multiplied by 1 - 1.15; the dosage of PAM is 3 - 5 mg / L, and the dosage of PFS is 100 - 150 mg / L. The water produced by the high - density sedimentation tank 11 then passes through the quartz sand filter 12 to remove suspended solids in the wastewater; afterwards, it passes through the submerged ultra - filtration membrane 13 to further remove turbidity and suspended solids, thus completing the pretreatment of the wastewater to obtain pretreated product water. And in the pretreated product water, the calcium ion concentration < 40 mg / L, the magnesium ion concentration < 20 mg / L, the suspended solid content < 0.1 mg / L, and the turbidity < 3 NTU;

[0052] Process 2 - Preliminary Concentration: The pretreated product water obtained in Process 1 - Pretreatment is sent into the reverse osmosis device 2 for preliminary concentration to obtain reverse osmosis concentrate and reverse osmosis product water. And the content of inorganic salts in the reverse osmosis concentrate is concentrated to 30000 mg / L - 35000 mg / L; the reverse osmosis product water is sent into the reuse water tank 4 for storage and standby;

[0053] Process 4 - Hardness Removal Treatment: The reverse osmosis concentrate obtained in Process 2 - Preliminary Concentration is sent into the ion - exchange device 5 to exchange and adsorb calcium ions and magnesium ions in the wastewater to obtain hardness - removed product water. And in the hardness - removed product water, the total concentration of scale - forming ions < 5 mg / L; the ion - exchange resin of the ion - exchange device 5 uses the weak - acid - type cation resin of Zheng Guang Resin Co., Ltd.;

[0054] Process 5 - Oxidation Treatment: The hardness - removed product water obtained in Process 4 - Hardness Removal Treatment is sent into the advanced oxidation device 6 for oxidation treatment. Utilizing the strong oxidizing property of hydroxyl radicals in the advanced oxidation device 6, organic substances are removed to obtain oxidized product water. And in the oxidized product water, the organic substance concentration < 300 mg / L. The oxidized product water is sent into Process 3 - High - fold Concentration for step - by - step concentration treatment through the high - fold concentration device 3.

[0055] Process Step 3: High-concentration Concentration: The oxidized effluent obtained in the process step of pentoxide treatment is sequentially fed into a multi-stage weak reverse osmosis membrane 31 for step-by-step concentration, and 20% - 50% of the total amount of the concentrated water of the next-stage weak reverse osmosis membrane 31 is refluxed to the permeate side of the previous-stage weak reverse osmosis membrane 31. By increasing the inorganic salt content on the permeate side of the previous-stage weak reverse osmosis membrane 31, the content of inorganic salts in the concentrated water side of the corresponding weak reverse osmosis membrane 31 is increased under a relatively low operating pressure (7 MPa). Furthermore, under the condition of a low osmotic pressure difference, high-fold concentration is achieved, and high-fold concentrated concentrated water and high-fold concentrated permeate are obtained. The content of inorganic salts in the high-fold concentrated concentrated water is concentrated to more than 180,000 mg / L. The high-fold concentrated concentrated water is fed into a concentrated water tank for storage and standby; the high-fold concentrated permeate is returned to the preliminary concentration in Process Step 2 to re-participate in the concentration treatment, thereby realizing the recycling of inorganic salts in the high-fold concentrated permeate and maximizing the recovery of salt ions in the effluent.

[0056] Example 3:

[0057] A process for treating wastewater using the novel membrane concentration system of Example 1 includes the following process steps: Process Step 1: Pretreatment; Process Step 2: Preliminary Concentration; Process Step 3: High-concentration Concentration; and also includes Process Step 4: Hardness Removal Treatment and Process Step 5: Oxidation Treatment; where:

[0058] Process Step 1: Pretreatment: The wastewater enters the pretreatment device 1. Specifically, the wastewater first enters the high-density sedimentation tank 11. By adding chemicals such as sodium carbonate, sodium hydroxide, hydrochloric acid, PAM, and PFS into the high-density sedimentation tank 11, substances such as calcium ions, magnesium ions, silicon dioxide, and suspended solids in the wastewater are removed. In this example, the specific water quality of the wastewater is: TDS content is 12,110 mg / L, SS is 21.5 mg / L, COD cr is 275.8 mg / L, total hardness is 483 mg / L, chloride ions are 4,076 mg / L, sulfate radicals are 2,243 mg / L, bicarbonate radicals are 962 mg / L, turbidity is 60 NTU, chromaticity is 25 times, and silicon dioxide is 25 mg / L.

[0059] Sodium carbonate 1,320 mg / L, sodium hydroxide 745 mg / L; hydrochloric acid 300 mg / L; the dosage of PAM is 3 mg / L, and the dosage of PFS is 100 mg / L are added to the wastewater. The effluent of the high-density sedimentation tank 11 then passes through a quartz sand filter 12 to remove the suspended solids in the wastewater; afterwards, it passes through a submerged ultrafiltration membrane 13 to further remove turbidity and suspended solids, thus completing the pretreatment of the wastewater and obtaining pretreatment effluent. The calcium ion concentration in the pretreatment effluent < 40 mg / L, the magnesium ion concentration < 20 mg / L, the suspended solid content < 0.1 mg / L, and the turbidity < 3 NTU;

[0060] Process 2: Preliminary concentration: Feed the pretreated water obtained in the pretreatment of Process 1 into the reverse osmosis device 2 for preliminary concentration to obtain reverse osmosis concentrated water and reverse osmosis product water, and the content of inorganic salts in the reverse osmosis concentrated water is concentrated to 32000 mg / L; Feed the reverse osmosis product water into the reuse water tank 4 for storage and standby;

[0061] Process 4: Hardness removal treatment: Feed the reverse osmosis concentrated water obtained in the preliminary concentration of Process 2 into the ion exchange device 5 to exchange and adsorb and remove calcium ions and magnesium ions in the wastewater to obtain hardness-removed product water, and the total concentration of scale-forming ions in the hardness-removed product water < 5 mg / L; The ion exchange resin of the ion exchange device 5 uses the weak acid-type cation resin of Zheng Guang Resin Co., Ltd.;

[0062] Process 5: Oxidation treatment: Feed the hardness-removed product water obtained in the hardness removal treatment of Process 4 into the advanced oxidation device 6 for oxidation treatment. Utilize the strong oxidizing property of hydroxyl radicals in the advanced oxidation device 6 to remove organic matter to obtain oxidized product water, and the organic matter concentration in the oxidized product water < 300 mg / L. Feed the oxidized product water into the high-fold concentration of Process 3 for step-by-step concentration treatment through the high-fold concentration device 3.

[0063] Process 3: High-fold concentration: Feed the oxidized product water obtained in the oxidation treatment of Process 5 into the multi-stage weak reverse osmosis membrane 31 for step-by-step concentration, and return 20% of the total amount of the concentrated water of the next-stage weak reverse osmosis membrane 31 to the product water side of the previous-stage weak reverse osmosis membrane 31. By increasing the content of inorganic salts on the product water side of the previous-stage weak reverse osmosis membrane 31, the content of inorganic salts in the concentrated water side of the corresponding weak reverse osmosis membrane 31 can be increased under a relatively low operating pressure (7 MPa), so as to achieve high-fold concentration under a low osmotic pressure difference, and obtain high-fold concentrated water and high-fold concentrated product water. The content of inorganic salts in the high-fold concentrated water is concentrated to 185000 mg / L. Feed the high-fold concentrated water into the concentrated water tank for storage and standby; The high-fold concentrated product water returns to the preliminary concentration of Process 2 to participate in the concentration treatment again, so as to realize the recycling of inorganic salts in the high-fold concentrated product water and maximize the recovery of salt ions in the product water.

[0064] Example 4:

[0065] As Figure 2 shown in the high-fold concentration device 3, it includes four-stage BC devices 31, and a reflux inlet is provided on the product water side of each previous-stage weak reverse osmosis membrane 31; The concentrated water outlet of the next-stage weak reverse osmosis membrane 31 is divided into two paths, one path is communicated with the inlet of the next-next-stage weak reverse osmosis membrane 31, and the other path is communicated with the reflux inlet on the product water side of the previous-stage weak reverse osmosis membrane 31.

[0066] In this embodiment, the weak reverse osmosis membrane 31 is an 8040-weak reverse osmosis membrane produced by Toyobo Co., Ltd. After the concentrated water first enters the first-stage weak reverse osmosis membrane 31 for concentration, the content of inorganic salts in the concentrated water generated by the first-stage weak reverse osmosis membrane 31 is concentrated to 50,000-60,000 mg / L; then the concentrated water enters the second-stage weak reverse osmosis membrane 31 for further concentration, so that the content of inorganic salts in the concentrated water generated by the second-stage weak reverse osmosis membrane 31 is concentrated to 80,000-90,000 mg / L; then the concentrated water enters the third-stage weak reverse osmosis membrane 31 for further concentration, so that the content of inorganic salts in the concentrated water generated by the third-stage weak reverse osmosis membrane 31 is concentrated to 130,000-140,000 mg / L; finally, the concentrated water enters the fourth-stage weak reverse osmosis membrane 31 for further concentration, so that the content of inorganic salts in the concentrated water generated by the fourth-stage weak reverse osmosis membrane 31 is concentrated to 180,000-200,000 mg / L.

[0067] In this embodiment, by opening a reflux inlet on the water production side of the weak reverse osmosis membrane 31, 20%-50% of the concentrated water of the next-stage weak reverse osmosis membrane 31 is refluxed to the water production side of the previous-stage weak reverse osmosis membrane 31. By increasing the content of inorganic salts on the water production side of the previous-stage weak reverse osmosis membrane 31, the content of inorganic salts in the concentrated water side of the corresponding weak reverse osmosis membrane 31 can be increased under a relatively low operating pressure (7 MPa), and thus high-fold concentration can be achieved under a low osmotic pressure difference; through the setting of multiple-stage weak reverse osmosis membranes 31, the content of inorganic salts in the finally obtained concentrated water reaches more than 1.5 times that of the traditional concentration system. Compared with the traditional system using an evaporation system to provide the concentration multiple, under the condition of reaching the same concentration multiple in advance, about 70% of the energy consumption can be saved, and the effect of energy conservation and consumption reduction is remarkable.

[0068] The weak reverse osmosis membrane 31 is made of a triacetate cellulose hydrophilic material. The material has stable performance, strong chlorine resistance, oxidation resistance, acid and alkali resistance, and can effectively reduce the fouling of substances such as microorganisms, organic matters, silicon dioxide, and calcium salts; after frequent cleaning, the system performance is stable and the membrane life is long; and it adopts a hollow fiber membrane structure to increase the specific surface area of the membrane. In this embodiment, the surface area of a single weak reverse osmosis membrane 31 reaches 900 m 2 , the flux is 0.7 LMH, and the water production volume can reach 630 L / h. Compared with the traditional spiral wound weak reverse osmosis membrane, the treatment capacity of a single weak reverse osmosis membrane 31 is increased by 2 times, and the treatment capacity is increased by 1 time compared with the high-pressure reverse osmosis membrane.

[0069] The maximum operating pressure involved in this system is 7 MPa, and the operating pressure is low, which avoids problems such as poor operating stability and high energy consumption caused by the membrane system under high pressure. The concentrated water concentration and operating pressure of various membrane devices in the traditional treatment system and the high-fold concentration device in this embodiment are shown in Table 1.

[0070] Table 1 Concentrations and Operating Pressure Gauges of Concentrated Water Produced by Various Membrane Devices

[0071]

[0072]

[0073] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A novel membrane concentration system, characterized in that, It includes a pretreatment device, a reverse osmosis device, and a high-concentration device; The concentrated water outlet of the submerged ultrafiltration membrane of the pretreatment device is connected to the water inlet of the reverse osmosis device. The concentrated water outlet of the reverse osmosis device is connected to the water inlet of the first-stage weak reverse osmosis membrane of the high-concentration device. The concentrated water outlet of the last-stage weak reverse osmosis membrane of the high-concentration device is connected to the water inlet of the concentrated water tank. The water production outlet of the reverse osmosis device is connected to the water inlet of the reused water tank. The water production outlets of multiple weak reverse osmosis membranes of the high-concentration device are all connected to the water inlet of the reverse osmosis device; The high-concentration device includes multiple stages of weak reverse osmosis membranes, and a reflux water inlet is provided on the water production side of each upper-stage weak reverse osmosis membrane; The concentrated water outlet of the lower-stage weak reverse osmosis membrane is divided into two paths. One path is connected to the water inlet of the next-lower-stage weak reverse osmosis membrane, and the other path is connected to the reflux water inlet on the water production side of the upper-stage weak reverse osmosis membrane, and 20% - 50% of the total amount of concentrated water of the lower-stage weak reverse osmosis membrane is refluxed to the water production side of the upper-stage weak reverse osmosis membrane; It also includes an ion exchange device and an advanced oxidation device; The concentrated water outlet of the reverse osmosis device is connected to the water inlet of the ion exchange device. The water outlet of the ion exchange device is connected to the water inlet of the advanced oxidation device. The water outlet of the advanced oxidation device is connected to the water inlet of the first-stage weak reverse osmosis membrane of the high-concentration device.

2. The novel membrane concentration system according to claim 1, wherein The number of the weak reverse osmosis membranes is 4 - 8.

3. A novel membrane concentration system according to claim 1, wherein, The pretreatment device includes a high-density sedimentation tank, a quartz sand filter, and a submerged ultrafiltration membrane; The water outlet of the high-density sedimentation tank is connected to the water inlet of the quartz sand filter. The water production outlet of the quartz sand filter is connected to the water inlet of the submerged ultrafiltration membrane.

4. A process for treating wastewater using a novel membrane concentration system according to any one of claims 1-3, characterized in that, It includes the following processes: Process 1: Pretreatment; Process 2: Preliminary concentration; Process 3: High-concentration; where: Process 1: Pretreatment: Wastewater enters the pretreatment device to remove calcium ions, magnesium ions, silicon dioxide, suspended solids, turbidity, etc. in the wastewater to obtain pretreatment produced water, and in the pretreatment produced water, the calcium ion concentration < 40 mg / L, the magnesium ion concentration < 20 mg / L, the suspended solid content < 0.1 mg / L, and the turbidity < 3 NTU; Process 2: Preliminary concentration: The pretreatment produced water obtained in Process 1 of pretreatment is sent into the reverse osmosis device for preliminary concentration to obtain reverse osmosis concentrated water and reverse osmosis produced water, and the content of inorganic salts in the reverse osmosis concentrated water is concentrated to 30000 mg / L - 35000 mg / L; The reverse osmosis produced water is sent into the reused water tank for storage and standby; Process 3: High-concentration: The reverse osmosis concentrated water obtained in Process 2 of preliminary concentration is sent into the high-concentration device for high-concentration to obtain high-concentration concentrated water and high-concentration produced water, and the content of inorganic salts in the high-concentration concentrated water is concentrated to more than 180000 mg / L. The high-concentration concentrated water is sent into the concentrated water tank for storage and standby, and the high-concentration produced water returns to Process 2 of preliminary concentration to participate in the concentration treatment again.

5. The process for treating wastewater by a novel membrane concentration system according to claim 4, characterized in that In the high - multiple concentration of the third process, the reverse osmosis concentrated water obtained in the preliminary concentration of the second process is sequentially fed into a multi - stage weak reverse osmosis membrane for step - by - step concentration, and part of the concentrated water of the next - stage weak reverse osmosis membrane is returned to the water production side of the previous - stage weak reverse osmosis membrane.

6. The process for treating wastewater by a novel membrane concentration system according to claim 5, characterized in that, It further includes a fourth process of hardness removal treatment and a fifth process of oxidation treatment; Among them Fourth process of hardness removal treatment: The reverse osmosis concentrated water obtained in the preliminary concentration of the second process is fed into the ion exchange device to remove calcium ions and magnesium ions in the wastewater, obtaining hardness - removed produced water, and the total concentration of scale - forming ions in the hardness - removed produced water < 5 mg / L; Fifth process of oxidation treatment: The hardness - removed produced water obtained in the fourth process of hardness removal treatment is fed into the advanced oxidation device for oxidation treatment to remove organic matter, obtaining oxidized produced water, and the organic matter concentration in the oxidized produced water < 300 mg / L. The oxidized produced water is fed into the high - multiple concentration of the third process and is subjected to step - by - step concentration treatment through the high - multiple concentration device.

7. The process for treating wastewater by a novel membrane concentration system according to claim 4, characterized in that, In the pretreatment of the first process, the wastewater first enters the high - density sedimentation tank to remove substances such as calcium ions, magnesium ions, silicon dioxide, and suspended solids in the wastewater; then, it enters the quartz sand filter to remove the suspended solids in the wastewater; afterwards, it enters the submerged ultrafiltration membrane to further remove turbidity and suspended solids.

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