A device and method for simultaneously concentrating urban sewage and producing high-quality water

Abstract

The present invention discloses an apparatus and method for simultaneously concentrating municipal sewage and producing high-quality water. The apparatus includes an FO-ED coupling system consisting of an FO unit and an ED unit; the FO unit includes a feed liquid tank, an FO membrane assembly, and a concentration chamber; the FO membrane assembly includes an FO membrane; 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. The present invention utilizes the FO process to allow water molecules to spontaneously permeate from the feed liquid portion with a high water chemical potential to the draw liquid portion with a low water chemical potential, thereby forming a municipal sewage concentrate. The ED process re-concentrates the diluted draw liquid and obtains clean effluent. As a pre-process for ED, FO intercepts a large amount of organic pollutants and inorganic scaling ions in municipal sewage, effectively alleviating the problem of ED membrane fouling. The present invention simultaneously achieves long-term and stable concentration of municipal sewage, efficient recovery of draw liquid, and production of high-quality water.

Description

Technical Field

[0001] The invention relates to a device and method for synchronously 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 growth of urban populations, urban wastewater discharge has increased significantly, posing severe environmental challenges to human society. Furthermore, in many arid and semi-arid regions, freshwater resources are in short supply due to insufficient precipitation and the impact of climate change, leading to an increasingly severe water crisis. Therefore, centralized treatment and recycling of urban wastewater has become an increasingly important option for addressing water scarcity.

[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 does not require external pressure or only requires low pressure to operate. 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 in driving force caused by concentration polarization and the difficulty in recovering solutes in the draw liquid have become bottlenecks in the promotion and application of FO. Common draw liquid concentration and recovery methods include precipitation, heating and various membrane filtration methods (such as ultrafiltration, nanofiltration, reverse osmosis, membrane distillation), etc.

[0004] Electrodialysis (ED) is a separation technology that combines electrochemical processes and dialysis diffusion processes. Driven by an external DC electric field, anions and cations migrate through selective ion exchange membranes to the anode and cathode, respectively, to achieve the 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] Chinese patent document CN105417801A discloses a method and system for extracting fresh water from sewage by synergistically combining forward osmosis and electrodialysis. The method proposes a method for recovering the forward osmosis extract using electrodialysis. However, the forward osmosis and electrodialysis are two independent process stages in this method, without forming a coupled forward osmosis and electrodialysis system. This results in a complex operation process and the inability to simultaneously achieve the concentration of municipal sewage, the recovery of the extract, and the production of high-quality water. Furthermore, the method does not discuss in detail the specific effects of sewage treatment and the setting and optimization of process conditions. The stability, low carbon content, and high efficiency of 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 the 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 present invention can effectively alleviate the problem of ED membrane pollution by removing inorganic scaling ions and effectively alleviate the problem of ED membrane pollution. Moreover, through the setting and optimization of process conditions, the present invention can simultaneously achieve long-term stable urban sewage concentration, efficient recovery of drawn liquid and production of high-quality water.

[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 an FO unit and an ED unit;

[0008] The FO unit includes a feed liquid tank, an FO membrane assembly and a concentration chamber; the FO membrane assembly includes an FO membrane, and two sides of the FO membrane are respectively connected to a feed liquid channel and an extraction liquid channel; the feed liquid channel is connected to the feed liquid tank, and a feed liquid pump is provided on the feed liquid channel. One side of the FO membrane forms a feed liquid circulation loop through the feed liquid channel, the feed liquid pump and the feed liquid tank, and the feed liquid pump circulates the municipal sewage in the feed liquid tank in the feed liquid channel by pumping; the extraction liquid channel is connected to the concentration chamber, and a extraction liquid pump is provided on the extraction liquid channel. The other side of the FO membrane forms a extraction liquid circulation loop through the extraction liquid channel, the extraction liquid pump and the concentration chamber, 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 permeate 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, a municipal 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, 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, a concentration chamber pump is provided on the concentration chamber channel, the anion and cation exchange membrane forms a concentration chamber circulation loop through the concentration chamber channel, the concentration chamber pump and the concentration chamber, the concentration chamber pump circulates the solution in the concentration chamber in the concentration chamber channel by pumping; the concentration chamber circulation loop and the draw liquid circulation loop are coupled 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, a dilute chamber pump is provided on the dilute chamber channel, the anion and cation exchange membrane forms a dilute chamber circulation loop through the dilute chamber channel, the dilute chamber pump and the dilute chamber, the dilute chamber pump The solution in the dilute chamber is circulated in the dilute chamber channel by pumping; the concentrate chamber is connected to 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 to the electrode liquid tank through the electrode liquid channel, and an electrode liquid pump is provided 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 directionally to the concentrate chamber, 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 equipped with a concentrate 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.

[0011] In one embodiment of the present invention, the membranes 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 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, 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 side of the FO support layer to slow down concentration polarization.

[0014] In one embodiment of the present invention, the dimensions of the concentrated chamber channel, the dilute 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 delivery and circulation of the solution in the pipeline.

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

[0017] Step 1: Assemble the FO membrane module and ED membrane module using 1 L simulated municipal sewage as the feed solution, 0.5 M NaCl as the draw solution and dilute chamber solution, and 2 L 7% Na2SO4 as the electrode solution, and connect each channel to the circulation pipeline;

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

[0019] Step 3: At the start of operation, control the liquid level of the solution in the concentrated chamber to be level with the overflow branch pipe;

[0020] Step 4: When the system operation ends after 24 hours of operation or when the wastewater is concentrated 10 times by the FO process, stop the feed liquid pump, the draw liquid pump, the concentrate chamber pump, the dilute 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 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 particulate matter 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. This method combines the low-energy-consumption and high-retention FO process with the high-efficiency ion selective separation ED process. While the FO process concentrates the urban sewage, the diluted draw liquid is re-concentrated as the ED concentration chamber, and the ED dilution chamber separates clean effluent, achieving simultaneous concentration of urban sewage, recovery of draw liquid, and production of high-quality water. Furthermore, the present invention uses FO as a pre-process for ED, effectively retaining a large amount of organic pollutants and Ca in the urban sewage while concentrating the feed liquid. 2 + Mg 2+ PO4 2- and CO3 2- The present invention removes inorganic scaling ions such as ions, which significantly alleviate the ED membrane fouling problem. The present invention couples the concentrate chamber circulation loop with the draw liquid circulation loop in the concentrate chamber, integrating the draw liquid chamber and the concentrate chamber into an overflow container (concentrate chamber 3). When the volume of the solution exceeds the overflow line, it can stably overflow into the dilute chamber circulation system. Under the action of electric current, the anions and cations in the dilute chamber migrate directionally through the selective anion and cation exchange membrane to the concentrate chamber, where the draw liquid is recovered. At the same time, clean effluent is obtained in the dilute chamber, successfully achieving efficient recovery of the draw liquid. In addition, by adjusting and optimizing parameter conditions, the present invention achieves a more stable, low-carbon and efficient sewage treatment process for the FO-ED coupling system, which can simultaneously achieve 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 met the Class III standard in the "Surface Water Environmental Quality Standard" (GB 3838-2002). BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0027] Figure 3 Schematic diagram of the retention of scaling-prone ions during 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 clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall 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 includes a feed liquid tank 1, an FO membrane assembly 2 and a concentration chamber 3; the FO membrane assembly 2 includes an FO membrane 15, and both sides of the FO membrane 15 are connected to a feed liquid channel 17 and an extraction liquid channel 16 respectively.

[0033] Furthermore, 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 side of the FO support layer 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. 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 the 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. 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 the 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 provided 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. The electrode liquid pump 12 circulates the Na2SO4 solution in the electrode liquid tank 6 in the electrode liquid channel 19 by pumping; wherein, under the drive of the DC power supply 18, the anions and cations in the dilute chamber 5 pass through the selective anion and cation exchange membrane 20 and migrate directionally to the concentrated chamber 3, 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. 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. The ED unit has 5 pairs of anion and cation exchange membranes 20, 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 delivery and circulation of the solution in the pipeline.

[0043] The working principle of the apparatus for simultaneously concentrating municipal sewage and producing high-quality water provided in this embodiment is as follows: the feed liquid pump 8 circulates the municipal sewage in the feed liquid channel 17, and the draw liquid pump 9 circulates the NaCl solution in the draw liquid channel 16. Under the action of the osmotic pressure difference across the FO membrane, water molecules spontaneously permeate from the feed liquid portion with high water chemical potential to the draw liquid portion with low water chemical potential. Simultaneously, a municipal sewage concentrate is formed in the feed liquid tank 1. The permeation 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 into the dilution chamber 5. The concentrate chamber pump 10 circulates the solution in the concentrate chamber 3 in the concentrate 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 concentrate chamber 3 through the selective anion and cation exchange membrane 20, and the drawn liquid is recovered in the concentrate 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 the apparatus for simultaneously concentrating urban sewage and producing high-quality water provided in Example 1. The method includes the following steps:

[0046] Step 1: Assemble the FO membrane module and ED membrane module using 1 L of simulated municipal sewage as the feed solution, 0.5 M NaCl as the draw solution (concentrate solution) and dilute solution, and 2 L of 7% Na2SO4 as the electrode solution, and connect each channel to the circulation pipeline;

[0047] Step 2: Start the feed liquid pump, draw liquid pump, concentrate chamber pump, dilute chamber pump, and 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 stable, turn on the DC power supply of the ED unit and operate the coupling system in constant voltage mode. Preferably, the voltage is set to 6.5 V.

[0048] Step 3: At the start 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 solution in the concentrated chamber to the solution in the dilute chamber is set to 5:1;

[0049] Step 4: With the system running time of 24 hours as the end point, stop the feed liquid pump, extraction liquid pump, concentrated chamber pump, dilute chamber pump, and electrode liquid pump, turn off the DC power supply of the ED unit, and drain 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 period of operation, the effluent water quality meets the Class III standard in the "Surface Water Environmental Quality Standard" (GB 3838-2002). During the short-term 24-h operation of the feed liquid, the pollutants COD, NH3-N, TN, and TP are concentrated by 1.74 times, 1.18 times, 1.20 times, and 1.58 times, respectively, 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 the apparatus for simultaneously concentrating urban sewage and producing high-quality water provided in Example 1. The method includes the following steps:

[0056] Step 1: 1L of Yixing urban sewage was used as the feed solution, 0.5M NaCl was used as the draw solution (concentrate solution) and dilute solution, and 2L of 7% Na2SO4 was used as the electrode solution. The FO membrane module and ED membrane module were assembled and connected to the circulation pipeline.

[0057] Step 2: Start the feed liquid pump, draw liquid pump, concentrate chamber pump, dilute chamber pump, and 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 stable, turn on the DC power supply of the ED unit and operate the coupling system in constant voltage mode. Preferably, the voltage is set to 6.5 V.

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

[0059] Step 4: The FO process concentrates Yixing's urban sewage 10 times, marking the end of the system operation. After stopping the feed liquid pump, draw liquid pump, concentrate chamber pump, dilute chamber pump, and electrode liquid pump, the DC power supply of the ED unit is turned off, and the effluent of the FO-ED coupling system is discharged;

[0060] Step 5: Concentrating the feed liquid by 10 times is considered a cycle. Sampling is performed at the end of each cycle. The FO membrane is taken out for physical cleaning before continued use. 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 Water output of the FO-ED coupling system during 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 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 over the 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%, effectively alleviating the problem of ED membrane fouling. Therefore, the method of the present invention can simultaneously achieve long-term and 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. This method couples the FO process, which has low energy consumption and high interception capacity, with the ED process, which has high-efficiency and selective ion separation. While the FO process concentrates the urban sewage, the diluted draw liquid is re-concentrated as the ED concentration chamber, and the ED dilution chamber separates clean effluent, thus simultaneously achieving the concentration of urban sewage, the recovery of the 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 amount of organic pollutants and Ca in the urban sewage while concentrating the feed liquid. 2+ Mg 2+ PO4 2- and CO3 2-The present invention can remove inorganic scaling ions such as ions, which significantly alleviate the ED membrane fouling problem; the present invention couples the concentration chamber circulation loop with the draw liquid circulation loop in the concentration chamber 3, integrating 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, realizing the recovery of the draw liquid in the concentration chamber 3, and obtaining clean effluent in the dilute chamber 5, successfully realizing the efficient recovery of the draw liquid. In addition, the present invention adjusts and optimizes the parameter conditions to achieve a more stable, low-carbon and efficient sewage treatment process for the FO-ED coupling system, and can simultaneously achieve 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" (GB3838-2002).

[0068] Although the present invention has been disclosed above in terms of preferred embodiments, 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 consisting of a FO unit and an ED unit; The FO unit includes a feed liquid tank, an FO membrane assembly and a concentration chamber; the FO membrane assembly includes an FO membrane, and two sides of the FO membrane are respectively connected to a feed liquid channel and an extraction liquid channel; the feed liquid channel is connected to the feed liquid tank, and a feed liquid pump is provided on the feed liquid channel. One side of the FO membrane forms a feed liquid circulation loop through the feed liquid channel, the feed liquid pump and the feed liquid tank, and the feed liquid pump circulates the municipal sewage in the feed liquid tank in the feed liquid channel by pumping; the extraction liquid channel is connected to the concentration chamber, and a extraction liquid pump is provided on the extraction liquid channel. The other side of the FO membrane forms a extraction liquid circulation loop through the extraction liquid channel, the extraction liquid pump and the concentration chamber, 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 permeate 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, a municipal 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, 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, a concentration chamber pump is provided on the concentration chamber channel, the anion and cation exchange membrane forms a concentration chamber circulation loop through the concentration chamber channel, the concentration chamber pump and the concentration chamber, the concentration chamber pump circulates the solution in the concentration chamber in the concentration chamber channel by pumping; the concentration chamber circulation loop and the draw liquid circulation loop are coupled 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, a dilute chamber pump is provided on the dilute chamber channel, the anion and cation exchange membrane forms a dilute chamber circulation loop through the dilute chamber channel, the dilute chamber pump and the dilute chamber, the dilute chamber pump The solution in the dilute chamber is circulated in the dilute chamber channel by pumping; the concentrate chamber is connected to 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 to the electrode liquid tank through the electrode liquid channel, and an electrode liquid pump is provided 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 directionally to the concentrate chamber, 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 concentrate chamber channel and the dilute chamber channel are respectively equipped with a concentrate 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 side of the FO support layer 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 dilute 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, which realize stable delivery 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: Assemble the FO membrane module and ED membrane module using 1 L simulated municipal sewage as the feed solution, 0.5 M NaCl as the draw solution and dilute chamber solution, and 2 L 7% Na2SO4 as the electrode solution, and connect each channel to the circulation pipeline; Step 2: Turn on the feed liquid pump, draw liquid pump, concentrate chamber pump, dilute chamber pump, and electrode liquid pump. After exhausting the air in the system and ensuring the flow rate of the FO-ED coupling system is stable, turn on the DC power supply of the ED unit. Step 3: At the start of operation, control the liquid level of the solution in the concentrated chamber to be level with the overflow branch pipe; Step 4: When the system operation ends after 24 hours of operation or when the wastewater is concentrated 10 times by the FO process, stop the feed liquid pump, the draw liquid pump, the concentrate chamber pump, the dilute 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 step 1, a filtration pretreatment operation is added to the feed liquid. The filtration process uses a circulating water multi-purpose vacuum pump and a 0.45 μm microporous filter membrane to remove suspended matter and large particulate matter in real urban sewage. The FO membrane assembly method uses 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 the 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 step 2, the DC power supply of the ED unit is in constant voltage mode, with a voltage of 5 to 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.

Images