Device and method for synchronously concentrating urban sewage and producing high-quality water

Abstract

The invention discloses a device and a method for synchronously concentrating urban sewage and producing high-quality water. The device comprises an FO-ED coupling system consisting of an FO unit and an ED unit, the FO unit comprises a feed liquid tank, an FO membrane assembly and a concentration chamber; the FO membrane assembly comprises an FO membrane; the ED unit comprises a direct-current power supply, an ED membrane assembly, a light chamber and an electrode liquid tank; and the ED membrane component comprises an anion-cation exchange membrane and a titanium-coated ruthenium electrode plate connected with the anion-cation exchange membrane. According to the invention, water molecules spontaneously permeate from the feed liquid part with high water chemical potential to the draw liquid part with low water chemical potential in the FO process to form a municipal sewage concentrated solution at the same time, and the diluted draw liquid is re-concentrated in the ED process to obtain clean effluent at the same time. FO is used as a pre-process of ED, a large number of organic pollutants and inorganic ions prone to scaling in urban sewage are intercepted, and the problem of ED membrane pollution is effectively relieved. According to the invention, long-term stable urban sewage concentration, high-efficiency recovery of the draw solution and production of high-quality water are synchronously realized.

Description

Technical Field

[0001] The invention relates to a device and a method for simultaneously concentrating urban sewage and producing high-quality water, belonging to the technical field of sewage treatment. Background Art

[0002] With the rapid advancement of global urbanization and the rapid increase in urban population, the amount of urban sewage discharge has increased significantly, bringing severe environmental challenges to human society. At the same time, many arid and semi-arid areas are short of fresh water resources due to insufficient precipitation and the impact of climate change, and the water crisis is becoming increasingly severe. Therefore, centralized treatment and recycling of urban sewage has gradually become an important option to solve the shortage of water resources.

[0003] Forward osmosis (FO) is a membrane technology that uses the osmotic pressure difference on both sides of the membrane as the driving force and can operate without external pressure or only requires low pressure. Compared with other pressure-driven membrane water treatment technologies, it has significant advantages such as low energy consumption, low pollution tendency and high retention capacity. At present, the FO process has been applied to many industries such as seawater desalination, sewage treatment, food processing, pharmaceuticals and power generation. However, the reduction of driving force caused by concentration polarization and the difficulty in recovering solutes in the draw liquid have become bottlenecks for the promotion and application of FO. Common methods for extract liquid concentration and recovery include precipitation method, heating method and various membrane filtration methods (such as ultrafiltration, nanofiltration, reverse osmosis, membrane distillation), etc.

[0004] Electrodialysis (ED) technology is a separation technology that combines electrochemical processes and dialysis diffusion processes. Driven by an external DC electric field, anions and cations migrate to the anode and cathode through selective ion exchange membranes, respectively, to achieve separation and concentration of ions in water. Although ED has many advantages such as high separation efficiency, flexible operation, and low energy consumption, it still faces some challenges and limitations. For example, changes in influent water quality and membrane fouling are important factors restricting its widespread application. Therefore, optimizing system design to reduce membrane fouling and improve the long-term stability and economy of electrodialysis technology is one of the current research focuses.

[0005] The Chinese patent document with publication number CN105417801A discloses a method and system for extracting fresh water from sewage by forward osmosis and electrodialysis. It proposes a method of recovering forward osmosis extraction liquid by electrodialysis. However, in this method, forward osmosis and electrodialysis are two independent process stages, and no forward osmosis and electrodialysis coupling system is formed, which makes its operation process more complicated and unable to simultaneously realize the concentration of urban sewage, the recovery of extraction liquid and the production of high-quality water. In addition, the method does not discuss in detail the specific effects of sewage treatment and the setting and optimization of process conditions, and its stability, low carbon and high efficiency in the sewage treatment process need to be further improved. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a device and method for simultaneously concentrating urban sewage and producing high-quality water. While the FO process of the present invention concentrates urban sewage, the diluted draw liquid is re-concentrated as an ED concentration chamber, and the ED dilution chamber separates clean effluent. In addition, FO, as a pre-process of ED, intercepts a large amount of organic pollutants and Ca in urban sewage. 2+ Mg 2+ PO4 3- and CO3 2- The inorganic scaling ions and the like can effectively alleviate the ED membrane pollution problem; and the present invention can simultaneously achieve long-term stable urban sewage concentration, efficient recovery of drawn liquid and production of high-quality water through the setting and optimization of process conditions.

[0007] The first object of the present invention is to provide a device for simultaneously concentrating urban sewage and producing high-quality water, comprising a FO-ED coupling system consisting of a FO unit and an ED unit;

[0008] The FO unit comprises a feed liquid tank, an FO membrane assembly and a concentration chamber; the FO membrane assembly comprises an FO membrane, and the two sides of the FO membrane are respectively connected with a feed liquid channel and an extraction liquid channel; the feed liquid channel is communicated with the feed liquid tank, and a feed liquid pump is arranged on the feed liquid channel, and a feed liquid circulation loop is formed between the feed liquid channel, the feed liquid pump and the feed liquid tank on one side of the FO membrane, and the feed liquid pump circulates the urban sewage in the feed liquid tank in the feed liquid channel by pumping; the extraction liquid channel is communicated with the concentration chamber, and an extraction liquid pump is arranged on the extraction liquid channel, and an extraction liquid circulation loop is formed between the extraction liquid channel, the extraction liquid pump and the concentration chamber on the other side of the FO membrane, and the extraction liquid pump circulates the solution in the concentration chamber in the extraction liquid channel by pumping; under the action of the osmotic pressure difference on both sides of the FO membrane, water molecules penetrate from the feed liquid part with high water chemical potential to the extraction liquid part with low water chemical potential, and at the same time, urban sewage concentrate is formed in the feed liquid tank;

[0009] The ED unit includes a DC power supply, an ED membrane assembly, a dilute chamber and an electrode liquid tank; the ED membrane assembly includes an anion and cation exchange membrane, and a titanium-coated ruthenium electrode plate connected to the anion and cation exchange membrane, and the positive and negative electrodes of the DC power supply are respectively connected to the anode and cathode of the titanium-coated ruthenium electrode plate; the two sides of the anion and cation exchange membrane are connected to the concentration chamber through a concentration chamber channel, and a concentration chamber pump is arranged on the concentration chamber channel, and the anion and cation exchange membrane forms a concentration chamber circulation loop with the concentration chamber through the concentration chamber channel, the concentration chamber pump and the concentration chamber, and the concentration chamber pump circulates the solution in the concentration chamber in the concentration chamber channel by pumping; the concentration chamber circulation loop is coupled with the draw liquid circulation loop in the concentration chamber; the two sides of the anion and cation exchange membrane are connected to the dilute chamber through the dilute chamber channel, and a dilute chamber pump is arranged on the dilute chamber channel, and the anion and cation exchange membrane forms a dilute chamber circulation loop with the dilute chamber through the dilute chamber channel, the dilute chamber pump and the dilute chamber, and the dilute chamber pump The solution in the dilute chamber is circulated in the dilute chamber channel by pumping; the concentrate chamber is connected with the dilute chamber through an overflow branch pipe; the water molecule penetration process of the FO unit increases the volume of the solution in the concentrate chamber, and when it exceeds the overflow line in the concentrate chamber, the solution in the concentrate chamber overflows into the dilute chamber; both sides of the anion and cation exchange membrane are connected with the electrode liquid tank through the electrode liquid channel, and an electrode liquid pump is arranged on the electrode liquid channel. The anion and cation exchange membrane forms an electrode liquid circulation loop through the electrode liquid channel, the electrode liquid pump and the electrode liquid tank, and the electrode liquid pump circulates the solution in the electrode liquid tank in the electrode liquid channel by pumping; wherein, driven by the DC power supply, the anions and cations in the dilute chamber pass through the selective anion and cation exchange membrane and migrate to the concentrate chamber in a direction manner, so that the drawn liquid is recovered in the concentrate chamber, and clean effluent is obtained in the dilute chamber at the same time, and the increased volume of the solution in the dilute chamber is equal to the water penetration volume of the FO unit.

[0010] In one embodiment of the present invention, the concentrate chamber channel and the dilute chamber channel are respectively installed with an online conductivity detector for the concentrate chamber and the online conductivity detector for the dilute chamber for real-time monitoring of the concentration of the draw liquid and the effluent conductivity of the FO-ED coupling system.

[0011] In one embodiment of the present invention, the membrane sheets of the anion and cation exchange membranes are separated by polypropylene partitions, and the anion and cation exchange membranes are alternately arranged between the titanium-coated ruthenium electrode plates.

[0012] In one embodiment of the present invention, the ED unit has 5 pairs of anion and cation exchange membranes, with an effective membrane area of ​​90.25 cm 2 .

[0013] In one embodiment of the present invention, the size of the feed liquid channel and the draw liquid channel of the FO unit is 8.5 cm×3.9 cm×0.2 cm, and the FO membrane is a triacetate cellulose membrane with an effective membrane area of ​​33.15 cm 2At the same time, a gasket with a thickness of 0.5 mm and a hole size of 2.5 mm × 2.5 mm was placed on the FO support layer side to slow down concentration polarization.

[0014] In one embodiment of the present invention, the dimensions of the concentrated chamber channel, the diluted chamber channel, and the electrode chamber channel of the ED unit are 9.5 cm×9.5 cm×0.09 cm.

[0015] In one embodiment of the present invention, the feed liquid pump, the draw liquid pump, the concentrated chamber pump, the dilute chamber pump, and the electrode liquid pump are all peristaltic pumps, and the peristaltic pumps are used to achieve stable transportation and circulation of the solution in the pipeline.

[0016] The second object of the present invention is to provide a method for simultaneously concentrating urban sewage and producing high-quality water, using the device for simultaneously concentrating urban sewage and producing high-quality water, the method comprising the following steps:

[0017] Step 1: 1L simulated urban sewage is used as feed solution, 0.5M NaCl is used as draw solution and dilute room solution, 2L 7% Na2SO4 is used as electrode solution, FO membrane module and ED membrane module are assembled, and each channel is connected to the circulation pipeline;

[0018] Step 2: Turn on the feed liquid pump, the draw liquid pump, the concentrated chamber pump, the dilute chamber pump, and the electrode liquid pump, and after exhausting the air in the system and ensuring that the flow of the FO-ED coupling system is stable, turn on the DC power supply of the ED unit;

[0019] Step 3: At the beginning of operation, the liquid level in the concentrated chamber is controlled to be level with the overflow branch pipe;

[0020] Step 4: When the system operation ends after 24 hours of operation or when the sewage is concentrated 10 times by the FO process, stop the feed liquid pump, the absorption liquid pump, the concentration chamber pump, the dilution chamber pump, and the electrode liquid pump, turn off the DC power supply of the ED unit, and discharge the effluent of the FO-ED coupling system.

[0021] In one embodiment of the present invention, in the step 1, the feed liquid is subjected to a filtration pretreatment operation, and the filtration process adopts a circulating water multi-purpose vacuum pump and a 0.45 μm microporous filter membrane to remove suspended matter and large particles in real urban sewage; the FO membrane assembly method selects the active layer of the forward osmosis membrane to face the feed liquid (AL-FS mode); the COD of the urban sewage is 100-300 mg / L, NH3-N is 25-40 mg / L, TN is 30-50 mg / L, TP is 1-3 mg / L, and pH is 6-8.

[0022] In one embodiment of the present invention, in the step 1, the volume ratio of the solution in the initial concentrated chamber to the solution in the dilute chamber is 3:1 to 5:1, preferably, the volume ratio of the solution in the concentrated chamber to the solution in the dilute chamber is 5:1; in the step 2, the DC power supply of the ED unit is in constant voltage mode, the voltage is 5 to 7V, preferably, the voltage is 6.5V; in the step 2, the peristaltic pump speed of the FO unit is 300ml / min, and the peristaltic pump speed of the ED unit is 100ml / min to 300ml / min, preferably, the peristaltic pump speed of the ED unit is 300ml / min.

[0023] Beneficial effects of the present invention:

[0024] The present invention provides a device and method for simultaneously concentrating urban sewage and producing high-quality water. The FO process with low energy consumption and high interception capacity and the ED process with high-efficiency selective separation of ions are coupled in a new way. While the FO process concentrates urban sewage, the diluted draw liquid is re-concentrated as the ED concentration chamber, and the ED dilution chamber separates clean effluent, thereby simultaneously achieving the concentration of urban sewage, the recovery of draw liquid and the production of high-quality water. In addition, the present invention uses FO as the pre-process of ED, and while concentrating the feed liquid, it effectively intercepts a large amount of organic pollutants and Ca in urban sewage. 2 + Mg 2+ PO4 2- and CO3 2- The invention can significantly alleviate the problem of ED membrane pollution by coupling the concentration chamber circulation loop with the draw liquid circulation loop in the concentration chamber, integrating the draw liquid chamber and the concentration chamber into an overflow container (concentration chamber 3), and when the volume of the solution exceeds the overflow line, it can stably overflow to the dilute chamber circulation system; under the action of electric current, the anions and cations in the dilute chamber pass through the selective anion and cation exchange membrane and migrate to the concentration chamber in a directional manner, and the draw liquid is recovered in the concentration chamber, and clean effluent is obtained in the dilute chamber, and the efficient recovery of the draw liquid is successfully achieved. In addition, the invention realizes a more stable, low-carbon and efficient sewage treatment process of the FO-ED coupling system by adjusting and optimizing the parameter conditions, and can simultaneously realize long-term stable urban sewage concentration, efficient recovery of draw liquid and production of high-quality water. After 15 days of long-term operation, the effluent of the optimized FO-ED coupling system meets the Class III standard in the "Surface Water Environmental Quality Standard" (GB 3838-2002). BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of a device for simultaneously concentrating urban sewage and producing high-quality water provided by the present invention.

[0026] Figure 2It is a schematic diagram of the change of the conductivity of the draw liquid during long-term operation of the FO-ED coupling system of the present invention.

[0027] Figure 3 It is a schematic diagram of the interception of easily scaling ions in the long-term operation of the FO-ED coupling system of the present invention.

[0028] In the figure: 1. feed liquid tank; 2. FO membrane assembly; 3. concentrate chamber; 4. ED membrane assembly; 5. dilute chamber; 6. electrode liquid tank; 7. overflow branch; 8. feed liquid pump; 9. draw liquid pump; 10. concentrate chamber pump; 11. dilute chamber pump; 12. electrode liquid pump; 13. concentrate chamber online conductivity detector; 14. dilute chamber online conductivity detector; 15. FO membrane; 16. draw liquid channel; 17. feed liquid channel; 18. DC power supply; 19. electrode liquid channel; 20. anion and cation exchange membrane; 21. concentrate chamber channel; 22. dilute chamber channel; 23. titanium-coated ruthenium electrode plate. DETAILED DESCRIPTION

[0029] 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 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.

[0030] Example 1

[0031] like Figure 1 As shown, this embodiment provides a device for simultaneously concentrating urban sewage and producing high-quality water, including a FO-ED coupling system consisting of a FO unit and an ED unit.

[0032] Furthermore, the FO unit comprises a feed liquid tank 1, a FO membrane assembly 2 and a concentration chamber 3; the FO membrane assembly 2 comprises a FO membrane 15, and two sides of the FO membrane 15 are respectively connected with a feed liquid channel 17 and an extraction liquid channel 16.

[0033] Further, the feed liquid channel 17 is connected to the feed liquid tank 1, and a feed liquid pump 8 is provided on the feed liquid channel 17. A feed liquid circulation loop is formed between one side of the FO membrane 15 through the feed liquid channel 17, the feed liquid pump 8 and the feed liquid tank 1, and the feed liquid pump 8 circulates the urban sewage in the feed liquid tank 1 in the feed liquid channel 17 by pumping; the draw liquid channel 16 is connected to the concentration chamber 3, and a draw liquid pump 9 is provided on the draw liquid channel 16. A draw liquid circulation loop is formed between the other side of the FO membrane 15 through the draw liquid channel 16, the draw liquid pump 9 and the concentration chamber 3, and the draw liquid pump 9 circulates the solution in the concentration chamber 3 in the draw liquid channel 16 by pumping; under the action of the osmotic pressure difference on both sides of the FO membrane 15, water molecules spontaneously penetrate from the feed liquid part with high water chemical potential to the draw liquid part with low water chemical potential, and at the same time, urban sewage concentrate is formed in the feed liquid tank 1.

[0034] Preferably, the FO membrane 15 is a triacetate cellulose membrane with an effective membrane area of ​​33.15 cm 2 At the same time, a gasket with a thickness of 0.5 mm and a hole size of 2.5 mm × 2.5 mm was placed on the FO support layer side to slow down concentration polarization.

[0035] Preferably, the size of the feed liquid channel 17 and the draw liquid channel 16 of the FO unit is 8.5 cm×3.9 cm×0.2 cm.

[0036] Furthermore, the ED unit includes a DC power supply 18, an ED membrane assembly 4, a dilute chamber 5 and an electrode liquid tank 6; the ED membrane assembly 4 includes an anion and cation exchange membrane 20, and a titanium-coated ruthenium electrode plate 23 connected to the anion and cation exchange membrane 20, the membrane sheets of the anion and cation exchange membrane 20 are separated by a polypropylene partition, the positive and negative electrodes of the DC power supply 18 are respectively connected to the anode and cathode of the titanium-coated ruthenium electrode plate 23 through alligator clip copper wires, and the anion and cation exchange membranes 20 are alternately arranged between the titanium-coated ruthenium electrode plates 23.

[0037] Furthermore, both sides of the anion and cation exchange membrane 20 are connected to the concentration chamber 3 through the concentration chamber channel 21, and a concentration chamber pump 10 is provided on the concentration chamber channel 21. The anion and cation exchange membrane 20 forms a concentration chamber circulation loop through the concentration chamber channel 21, the concentration chamber pump 10 and the concentration chamber 3. The concentration chamber pump 10 circulates the solution in the concentration chamber 3 in the concentration chamber channel 21 by pumping; the concentration chamber circulation loop and the draw liquid circulation loop are coupled in the concentration chamber 3.

[0038] Furthermore, both sides of the anion and cation exchange membrane 20 are connected to the dilute chamber 5 through a dilute chamber channel 22, and a dilute chamber pump 11 is provided on the dilute chamber channel 22. The anion and cation exchange membrane 20 forms a dilute chamber circulation loop through the dilute chamber channel 22, the dilute chamber pump 11 and the dilute chamber 5, and the dilute chamber pump 11 circulates the solution in the dilute chamber 5 in the dilute chamber channel 22 by pumping; the concentration chamber 3 is connected to the dilute chamber 5 through an overflow branch pipe 7; the water molecule penetration process of the FO unit increases the volume of the solution in the concentration chamber 3, and when it exceeds the overflow line in the concentration chamber 3, the solution in the concentration chamber 3 overflows into the dilute chamber 5.

[0039] Furthermore, both sides of the anion and cation exchange membrane 20 are connected to the electrode liquid tank 6 through the electrode liquid channel 19, and the electrode liquid pump 12 is arranged on the electrode liquid channel 19. The anion and cation exchange membrane 20 forms an electrode liquid circulation loop through the electrode liquid channel 19, the electrode liquid pump 12 and the electrode liquid tank 6, and the electrode liquid pump 12 circulates the Na2SO4 solution in the electrode liquid tank 6 in the electrode liquid channel 19 by pumping; wherein, driven by the DC power supply 18, the anions and cations in the dilute chamber 5 are directed to migrate to the concentrated chamber 3 through the selective anion and cation exchange membrane 20, and the drawn liquid is recovered in the concentrated chamber 3, and clean effluent is obtained in the dilute chamber 5 at the same time, and the increased volume of the solution in the dilute chamber 5 is equal to the water permeation volume of the FO unit.

[0040] Optionally, the concentrate chamber channel 21 and the dilute chamber channel 22 are respectively installed with a concentrate chamber online conductivity detector 13 and a dilute chamber online conductivity detector 14 for real-time monitoring of the concentration of the drawn liquid and the effluent conductivity of the FO-ED coupling system.

[0041] Preferably, the dimensions of the concentrated chamber channel 21, the dilute chamber channel 22, and the electrode chamber channel 19 are 9.5 cm×9.5 cm×0.09 cm, and the anion and cation exchange membranes 20 of the ED unit are 5 pairs in total, with an effective membrane area of ​​90.25 cm 2 .

[0042] Preferably, the feed liquid pump 8, the draw liquid pump 9, the concentrated chamber pump 10, the dilute chamber pump 11, and the electrode liquid pump 12 are all peristaltic pumps, and the peristaltic pumps are used to achieve stable transportation and circulation of the solution in the pipeline.

[0043] The working principle of the device for simultaneously concentrating urban sewage and producing high-quality water provided in this embodiment is as follows: the feed liquid pump 8 circulates the urban sewage in the feed liquid channel 17 by pumping, and the draw liquid pump 9 circulates the NaCl solution in the draw liquid channel 16 by pumping. Under the action of the osmotic pressure difference on both sides of the FO membrane, water molecules spontaneously penetrate from the feed liquid part with high water chemical potential to the draw liquid part with low water chemical potential, and at the same time, urban sewage concentrate is formed in the feed liquid tank 1. The penetration process of water molecules in the FO unit increases the volume of the solution in the concentration chamber 3. When the volume exceeds the overflow line of the concentration chamber 3, the solution overflows to the dilution chamber 5. The concentration chamber pump 10 circulates the solution in the concentration chamber 3 in the concentration chamber channel 21 by pumping, the dilute chamber pump 11 circulates the solution in the dilute chamber 5 in the dilute chamber channel 22 by pumping, and the electrode liquid pump 12 circulates the Na2SO4 solution in the electrode liquid tank 6 in the electrode liquid channel 19 by pumping. Driven by the external DC power supply 18, the anions and cations in the dilute chamber 5 migrate directionally to the concentration chamber 3 through the selective anion and cation exchange membrane 20, and the drawn liquid is recovered in the concentration chamber 3. At the same time, clean effluent is obtained in the dilute chamber 5. The increased volume of the solution in the dilute chamber 5 is equal to the water permeation volume of the FO unit.

[0044] Example 2

[0045] This embodiment provides a method for simultaneously concentrating urban sewage and producing high-quality water, using a device for simultaneously concentrating urban sewage and producing high-quality water provided in Example 1, and the method comprises the following steps:

[0046] Step 1: 1L simulated urban sewage is used as feed solution, 0.5M NaCl is used as draw solution (concentrated chamber solution) and dilute chamber solution, 2L 7% Na2SO4 is used as electrode solution, FO membrane module and ED membrane module are assembled, and each channel is connected to the circulation pipeline;

[0047] Step 2: Turn on the feed liquid pump, the draw liquid pump, the concentrated chamber pump, the dilute chamber pump, and the electrode liquid pump. Preferably, the flow rate is set to 300 ml / min. After the air in the system is exhausted and the flow rate of the FO-ED coupling system is ensured to be stable, turn on the DC power supply of the ED unit and operate the coupling system in a constant voltage mode. Most preferably, the voltage is set to 6.5 V.

[0048] Step 3: At the beginning of operation, the liquid level of the solution in the concentrated chamber is controlled to be just level with the overflow branch pipe port. Most preferably, the initial volume ratio of the solution in the concentrated chamber to the solution in the dilute chamber is set to 5:1;

[0049] Step 4: Take the running time of 24h as the end point of the system operation, stop the feed liquid pump, absorption liquid pump, concentrated chamber pump, dilute chamber pump, electrode liquid pump, turn off the DC power supply of the ED unit, and discharge the effluent of the FO-ED coupling system.

[0050] Preferably, the COD of the simulated urban sewage is 200-300 mg / L, NH3-N is 30-40 mg / L, TN is 40-50 mg / L, TP is 1.5-3 mg / L, and pH is about 7.

[0051] Table 1 Feed liquid concentration and system effluent conditions of the short-term operation of the FO-ED coupling system

[0052]

[0053] The experimental results are shown in Table 1 above. It can be seen that after the simulated domestic sewage is treated by the FO-ED coupling system in a short-term operation, the effluent water quality meets the Class III standard in the "Surface Water Environmental Quality Standard" (GB 3838-2002), and the pollutants COD, NH3-N, TN, and TP in the feed liquid are concentrated by 1.74 times, 1.18 times, 1.20 times, and 1.58 times respectively during the short-term 24-h operation, indicating that the device can achieve the simultaneous concentration of urban sewage and the production of high-quality water.

[0054] Example 3

[0055] This embodiment provides a method for simultaneously concentrating urban sewage and producing high-quality water, using a device for simultaneously concentrating urban sewage and producing high-quality water provided in Example 1, and the method comprises the following steps:

[0056] Step 1: 1L of Yixing urban sewage is used as feed solution, 0.5M NaCl is used as draw solution (concentrated chamber solution) and dilute chamber solution, 2L of 7% Na2SO4 is used as electrode solution, FO membrane module and ED membrane module are assembled, and each channel is connected to the circulation pipeline;

[0057] Step 2: Turn on the feed liquid pump, the draw liquid pump, the concentrated chamber pump, the dilute chamber pump, and the electrode liquid pump. Preferably, the flow rate is set to 300 ml / min. After the air in the system is exhausted and the flow rate of the FO-ED coupling system is ensured to be stable, turn on the DC power supply of the ED unit and operate the coupling system in a constant voltage mode. Most preferably, the voltage is set to 6.5 V.

[0058] Step 3: At the beginning of operation, the liquid level in the concentrated chamber is controlled to be just level with the overflow branch pipe. Most preferably, the initial volume ratio of the concentrated and diluted chambers is set to 5:1;

[0059] Step 4: The FO process concentrates the urban sewage of Yixing City by 10 times as the end point of the system operation, stops the feed liquid pump, the absorption liquid pump, the concentrated chamber pump, the dilute chamber pump, and the electrode liquid pump, and then turns off the DC power supply of the ED unit to discharge the effluent of the FO-ED coupling system;

[0060] Step 5: Concentrating the feed liquid by 10 times is considered as one cycle. Sampling is performed at the end of each cycle. The FO membrane is taken out for physical cleaning and then continued to be used. The experiment is run continuously for 5 cycles (15 days).

[0061] Preferably, the COD of the Yixing urban sewage is 100-200 mg / L, NH3-N is 25-30 mg / L, TN is 30-35 mg / L, TP is 1-2 mg / L, and pH is about 7.

[0062] Table 2 Feed liquid concentration of long-term operation of FO-ED coupling system

[0063]

[0064] Table 3 System water discharge of FO-ED coupling system in long-term operation

[0065]

[0066] The experimental results are shown in Table 2, Table 3 and Figure 2 , Figure 3 As shown in the figure, it can be seen that under the long-term operation of the FO-ED coupling system, the concentration multiple of the feed liquid pollutants is greatly improved compared with the short-term operation. At the same time, the treated urban sewage in Yixing City still meets the Class III standard in the "Surface Water Environmental Quality Standard" (GB 3838-2002). In addition, the conductivity of the draw liquid as the concentration chamber of ED is basically unchanged in five cycles, indicating that the ED process has a good effect on the recovery of the draw liquid. 2+ Mg 2+ PO4 3- and CO3 2- The removal rate of scaling ions is higher than 97%, which effectively alleviates the ED membrane pollution problem. Therefore, the method of the present invention can simultaneously achieve long-term stable urban sewage concentration, efficient recovery of drawn liquid and production of high-quality water.

[0067] In summary, the present invention provides a device and method for simultaneously concentrating urban sewage and producing high-quality water, which couples the FO process with low energy consumption and high interception capacity with the ED process with high-efficiency selective separation of ions in a new way, so that while the FO process concentrates urban sewage, the diluted draw liquid is re-concentrated as the ED concentration chamber, and the ED dilution chamber separates clean effluent, thereby simultaneously achieving the concentration of urban sewage, the recovery of draw liquid, and the production of high-quality water. In addition, the present invention uses FO as a pre-process for ED, which effectively intercepts a large number of organic pollutants and Ca in urban sewage while concentrating the feed liquid. 2+ Mg 2+ PO4 2- and CO3 2-The present invention can significantly alleviate the ED membrane pollution problem by coupling the concentration chamber circulation loop with the draw liquid circulation loop in the concentration chamber 3, so as to realize the integration of the draw liquid chamber and the concentration chamber into an overflow container (concentration chamber 3). When the volume of the solution exceeds the overflow line, it can stably overflow to the dilute chamber circulation system; under the action of electric current, the anions and cations in the dilute chamber 5 pass through the selective anion and cation exchange membrane 20 and migrate to the concentration chamber 3, so as to realize the recovery of the draw liquid in the concentration chamber 3, and obtain clean effluent in the dilute chamber 5, so as to successfully realize the efficient recovery of the draw liquid. In addition, the present invention can realize a more stable, low-carbon and efficient sewage treatment process of the FO-ED coupling system by adjusting and optimizing the parameter conditions, and can simultaneously realize the long-term stable concentration of urban sewage, efficient recovery of draw liquid and production of high-quality water. After 15 days of long-term operation, the effluent of the optimized FO-ED coupling system meets the Class III standard in the "Surface Water Environmental Quality Standard" (GB3838-2002).

[0068] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A device for simultaneously concentrating urban sewage and producing high-quality water, characterized in that: A FO-ED coupling system comprising a FO unit and an ED unit; The FO unit comprises a feed liquid tank, an FO membrane assembly and a concentration chamber; the FO membrane assembly comprises an FO membrane, and the two sides of the FO membrane are respectively connected with a feed liquid channel and an extraction liquid channel; the feed liquid channel is communicated with the feed liquid tank, and a feed liquid pump is arranged on the feed liquid channel, and a feed liquid circulation loop is formed between the feed liquid channel, the feed liquid pump and the feed liquid tank on one side of the FO membrane, and the feed liquid pump circulates the urban sewage in the feed liquid tank in the feed liquid channel by pumping; the extraction liquid channel is communicated with the concentration chamber, and an extraction liquid pump is arranged on the extraction liquid channel, and an extraction liquid circulation loop is formed between the extraction liquid channel, the extraction liquid pump and the concentration chamber on the other side of the FO membrane, and the extraction liquid pump circulates the solution in the concentration chamber in the extraction liquid channel by pumping; under the action of the osmotic pressure difference on both sides of the FO membrane, water molecules penetrate from the feed liquid part with high water chemical potential to the extraction liquid part with low water chemical potential, and at the same time, urban sewage concentrate is formed in the feed liquid tank; The ED unit includes a DC power supply, an ED membrane assembly, a dilute chamber and an electrode liquid tank; the ED membrane assembly includes an anion and cation exchange membrane, and a titanium-coated ruthenium electrode plate connected to the anion and cation exchange membrane, and the positive and negative electrodes of the DC power supply are respectively connected to the anode and cathode of the titanium-coated ruthenium electrode plate; the two sides of the anion and cation exchange membrane are connected to the concentration chamber through a concentration chamber channel, and a concentration chamber pump is arranged on the concentration chamber channel, and the anion and cation exchange membrane forms a concentration chamber circulation loop with the concentration chamber through the concentration chamber channel, the concentration chamber pump and the concentration chamber, and the concentration chamber pump circulates the solution in the concentration chamber in the concentration chamber channel by pumping; the concentration chamber circulation loop is coupled with the draw liquid circulation loop in the concentration chamber; the two sides of the anion and cation exchange membrane are connected to the dilute chamber through the dilute chamber channel, and a dilute chamber pump is arranged on the dilute chamber channel, and the anion and cation exchange membrane forms a dilute chamber circulation loop with the dilute chamber through the dilute chamber channel, the dilute chamber pump and the dilute chamber, and the dilute chamber pump The solution in the dilute chamber is circulated in the dilute chamber channel by pumping; the concentrate chamber is connected with the dilute chamber through an overflow branch pipe; the water molecule penetration process of the FO unit increases the volume of the solution in the concentrate chamber, and when it exceeds the overflow line in the concentrate chamber, the solution in the concentrate chamber overflows into the dilute chamber; both sides of the anion and cation exchange membrane are connected with the electrode liquid tank through the electrode liquid channel, and an electrode liquid pump is arranged on the electrode liquid channel. The anion and cation exchange membrane forms an electrode liquid circulation loop through the electrode liquid channel, the electrode liquid pump and the electrode liquid tank, and the electrode liquid pump circulates the solution in the electrode liquid tank in the electrode liquid channel by pumping; wherein, driven by the DC power supply, the anions and cations in the dilute chamber pass through the selective anion and cation exchange membrane and migrate to the concentrate chamber in a direction manner, so that the drawn liquid is recovered in the concentrate chamber, and clean effluent is obtained in the dilute chamber at the same time, and the increased volume of the solution in the dilute chamber is equal to the water penetration volume of the FO unit.

2. The device for simultaneously concentrating urban sewage and producing high-quality water according to claim 1, characterized in that: The concentrated chamber channel and the dilute chamber channel are respectively equipped with a concentrated chamber online conductivity detector and a dilute chamber online conductivity detector for real-time monitoring of the concentration of the drawn liquid and the effluent conductivity of the FO-ED coupling system.

3. The device for simultaneously concentrating urban sewage and producing high-quality water according to claim 1, characterized in that: The membrane sheets of the anion and cation exchange membranes are separated by polypropylene partitions, and the anion and cation exchange membranes are alternately arranged between the titanium-coated ruthenium electrode plates.

4. The device for simultaneously concentrating urban sewage and producing high-quality water according to claim 3, characterized in that: The ED unit has 5 pairs of anion and cation exchange membranes, with an effective membrane area of ​​90.25 cm 2 .

5. The device for simultaneously concentrating urban sewage and producing high-quality water according to claim 1, characterized in that: The dimensions of the feed liquid channel and the draw liquid channel of the FO unit are 8.5 cm×3.9 cm×0.2 cm. The FO membrane is a triacetate cellulose membrane with an effective membrane area of ​​33.15 cm 2 At the same time, a gasket with a thickness of 0.5 mm and a hole size of 2.5 mm × 2.5 mm was placed on the FO support layer side to slow down concentration polarization.

6. The device for simultaneously concentrating urban sewage and producing high-quality water according to claim 1, characterized in that: The dimensions of the concentrated chamber channel, the diluted chamber channel, and the electrode chamber channel of the ED unit are 9.5 cm×9.5 cm×0.09 cm.

7. The device for simultaneously concentrating urban sewage and producing high-quality water according to claim 1, characterized in that: The feed liquid pump, the draw liquid pump, the concentrated chamber pump, the dilute chamber pump, and the electrode liquid pump are all peristaltic pumps, and the peristaltic pumps are used to achieve stable transportation and circulation of the solution in the pipeline.

8. A method for simultaneously concentrating urban sewage and producing high-quality water, characterized in that: A device for simultaneously concentrating urban sewage and producing high-quality water according to any one of claims 1 to 7 is used, and the method comprises the following steps: Step 1: 1L simulated urban sewage is used as feed solution, 0.5M NaCl is used as draw solution and dilute room solution, 2L 7% Na2SO4 is used as electrode solution, FO membrane module and ED membrane module are assembled, and each channel is connected to the circulation pipeline; Step 2: Turn on the feed liquid pump, the draw liquid pump, the concentrated chamber pump, the dilute chamber pump, and the electrode liquid pump, and after exhausting the air in the system and ensuring that the flow of the FO-ED coupling system is stable, turn on the DC power supply of the ED unit; Step 3: At the beginning of operation, the liquid level in the concentrated chamber is controlled to be level with the overflow branch pipe; Step 4: When the system operation ends after 24 hours of operation or when the sewage is concentrated 10 times by the FO process, stop the feed liquid pump, the absorption liquid pump, the concentration chamber pump, the dilution chamber pump, and the electrode liquid pump, turn off the DC power supply of the ED unit, and discharge the effluent of the FO-ED coupling system.

9. The method for simultaneously concentrating urban sewage and producing high-quality water according to claim 1, characterized in that: In the step 1, a filtration pretreatment operation is added to the feed liquid, and the filtration process adopts a circulating water multi-purpose vacuum pump and a 0.45 μm microporous filter membrane to remove suspended matter and large particles in real urban sewage; the FO membrane assembly method selects the active layer of the forward osmosis membrane to face the feed liquid; the COD of the urban sewage is 100-300 mg / L, NH3-N is 25-40 mg / L, TN is 30-50 mg / L, TP is 1-3 mg / L, and pH is 6-8.

10. The method for simultaneously concentrating urban sewage and producing high-quality water according to claim 1, characterized in that: In the step 1, the volume ratio of the solution in the initial concentrated chamber to the solution in the dilute chamber is 3:1 to 5:1; In the step 2, the DC power supply of the ED unit is in constant voltage mode, and the voltage is 5-7V; In the step 2, the peristaltic pump speed of the FO unit is 300 ml / min, and the peristaltic pump speed of the ED unit is 100 ml / min to 300 ml / min.

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