A system and method for treating nanofiltration concentrate from a landfill leachate

Abstract

The application discloses a kind of incineration plant percolate nanofiltration concentrated liquid processing system, it is related to sewage treatment technical field, including electrodialysis device, inorganic salt in nanofiltration concentrated liquid is separated, fresh water end of electrodialysis device is connected to nanofiltration device, macromolecular organic matter is concentrated, fresh water end of nanofiltration device is connected to reverse osmosis device, further removes inorganic salt, fresh water end of reverse osmosis device is connected to water production tank, concentrated water end of electrodialysis device is connected to hard removal device, concentrated liquid end of nanofiltration device is connected to ozone device, macromolecular organic matter is oxidized into small molecule organic matter, the other end of ozone device is connected to SBR device, drainage end of SBR device is connected to electrolytic device, drainage end of electrolytic device is connected to water production tank, and exhaust end is connected to tail gas absorption device;Drainage end of hard removal device, drainage end of tail gas absorption device is connected to evaporation device. Reach the effect that the effect of effectively treating nanofiltration concentrated liquid is achieved for strong pertinence, processing effect is good, and reagent cost is low.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a nanofiltration concentrate treatment system and method for incineration plant leachate. Background Technology

[0002] Whether incineration or sanitary landfill is used for municipal solid waste disposal, the challenge of leachate treatment remains. In 2008, my country promulgated the "Standard for Pollutant Control of Biological Waste Landfills" (GB 16889-2008), which significantly raised the standards for leachate treatment and discharge, and imposed strict controls on various major pollutants.

[0003] Landfill leachate is a waste liquid produced during landfilling due to physical, biological, and chemical processes such as gravity compaction and fermentation. It is characterized by complex water composition, high concentrations of pollutants such as COD and ammonia nitrogen, and significant environmental hazards. Because of stringent discharge standards for landfill leachate, biological treatment alone is insufficient to meet discharge requirements. Subsequent deep treatment using a dual-membrane method (nanofiltration membrane + reverse osmosis membrane) is generally employed to remove pollutants such as color, organic pollutants, and total dissolved solids.

[0004] Nanofiltration membranes are typically selected to intercept organic matter while also removing calcium and magnesium ions to some extent. This results in nanofiltration concentrates containing high concentrations of humic acid-like organic pollutants, high total hardness, and a dark brown color, making them difficult for waste-to-energy plants to process. If the concentrate is returned to the upstream biological treatment system, it will not only accumulate dissolved total solids, which can be toxic to microorganisms and affect the biochemical effect, increasing the operating load of the membrane process, but also easily cause scaling and clogging of equipment and pipelines. Advanced oxidation methods have high reagent costs and, although they can remove some organic pollutants, they cannot effectively remove dissolved total solids. Discharge to wastewater treatment plants or onto the ground still has a significant impact on the environment. Direct evaporation has disadvantages such as frequent equipment failures, difficulty in stable operation, short downtime cleaning cycles, and high operating costs.

[0005] Therefore, nanofiltration concentrate has become a difficult point in the treatment of leachate from waste incineration power plants, and there is an urgent need for a nanofiltration concentrate treatment system for incineration plant leachate to solve the above-mentioned technical problems. Summary of the Invention

[0006] The purpose of this invention is to provide a nanofiltration concentrate treatment system for incineration plant leachate, which is highly targeted, has good treatment effect, and has low reagent cost, and can effectively treat nanofiltration concentrate.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0008] A nanofiltration concentrate treatment system for incineration plant leachate includes an electrodialysis unit to separate inorganic salts from the nanofiltration concentrate; a desalination end of the electrodialysis unit is connected to the nanofiltration unit to concentrate high-molecular-weight organic matter; a desalination end of the nanofiltration unit is connected to a reverse osmosis unit to further remove inorganic salts; and a desalination end of the reverse osmosis unit is connected to a product water tank.

[0009] The concentrate end of the electrodialysis unit is connected to the hardening removal unit to remove total hardness, and the drain end of the hardening removal unit is connected to the evaporation unit; the concentrate end of the nanofiltration unit is connected to the ozone unit to oxidize high molecular organic matter into low molecular organic matter, and the other end of the ozone unit is connected to the SBR unit to remove substances including organic matter, ammonia nitrogen, and total phosphorus in wastewater.

[0010] Furthermore, the drain end of the SBR unit is connected to the electrolysis unit, the drain end of the electrolysis unit is connected to the product water tank, the exhaust end is connected to the tail gas absorption unit, and the drain end of the tail gas absorption unit is connected to the evaporation unit.

[0011] Furthermore, the sludge discharge ends of the hardening device, the SBR device, and the electrolysis device are all connected to the sludge dewatering device for mixing treatment.

[0012] Furthermore, the hardening removal device includes a primary reaction tank and a hardening removal membrane assembly. The top of the primary reaction tank is connected to a primary dosing pipe and a secondary dosing pipe, and the bottom of the primary reaction tank is connected to the secondary reaction tank through a flow passage.

[0013] The top of the secondary reaction tank is connected to the tertiary dosing pipe; the upper part of the secondary reaction tank is connected to the thickening tank through the flow hole; the lower part of the thickening tank is connected to the membrane module lift pump, and the outlet end of the membrane module lift pump is connected to the inlet end of the hard membrane module.

[0014] Ferric chloride is added via the first dosing tube, calcium hydroxide via the second dosing tube, and sodium hydroxide via the third dosing tube.

[0015] Furthermore, the concentrate end of the hard membrane removal module returns to the top of the concentration tank, the outlet end is connected to the intermediate water tank of the hard membrane removal unit, the bottom of the intermediate water tank of the hard membrane removal unit is connected to the intermediate water pump, the outlet end of the intermediate water pump is connected to the fourth dosing pipe, and hydrochloric acid is added through the fourth dosing pipe; the outlet of the intermediate water tank of the hard membrane removal unit also serves as the rinsing / cleaning water for the hard membrane removal module.

[0016] Furthermore, the evaporation device includes an evaporation water inlet pump, a compressor, and an evaporator. The inlet end of the evaporation water inlet pump is connected to the outlet end of the hardening device, and the outlet end is connected in sequence to the condensate preheater, the non-condensable steam preheater, and the evaporation water inlet pipe. The two inlets of the evaporator are respectively connected to the evaporation water inlet pipe and the outlet end of the compressor, and the inlet of the compressor is connected to the separator.

[0017] The liquid outlet of the evaporator is connected to the separator, the non-condensable vapor outlet of the evaporator is connected to the non-condensable vapor preheater, the outlet of the separator is connected to the circulating pump, and the outlet of the circulating pump is connected to the evaporator inlet pipe; the non-condensable vapor outlets of the evaporator and the condenser are connected to the condensate pump, and the outlet of the non-condensable vapor preheater is connected to the condenser to condense and reuse the non-condensable vapor from the evaporator.

[0018] Furthermore, the ozone device includes an ozone inlet pump, an ozone generator, and a contact reaction tower. The upper side of the contact reaction tower has an inlet connected to the ozone inlet pump, the lower side of the contact reaction tower has an ozone inlet connected to the ozone generator's outlet, and the lower side of the contact reaction tower has an outlet connected to the ozone device's water production tank. The contact reaction tower is filled with a catalyst, with an ozone dosage of 2.0-5.0 kg / t and a designed residence time of not less than 1.5 hours.

[0019] Furthermore, the SBR device is equipped with an inlet at the top connected to the SBR feed pump, a decanter at the top connected to the outlet connected to the SBR product water tank, an aeration pipeline at the bottom connected to an aeration blower, a sludge discharge port at the bottom connected to the SBR sludge discharge pump, and the outlet of the SBR sludge discharge pump connected to the sludge thickening tank.

[0020] When water is fed in, the agitator is turned on for stirring. After the anaerobic stage, the aeration blower is turned on to supply oxygen to the microorganisms in the device through microporous aeration. After the aerobic stage, the aeration blower is turned off to enter the sedimentation stage. Then, the effluent time of the SBR device is controlled by the decanter and the liquid level. The dissolved oxygen in the SBR device is controlled by the dissolved oxygen meter to be less than 0.5 mg / L in the influent stage, 2.0 mg / L in the aeration stage, and the sludge concentration is 5.0-6.0 g / L.

[0021] Furthermore, the electrolysis device includes an electrolysis cell, with the inlet of the electrolysis cell connected to the feed water pump of the electrolysis device, the outlet connected to the product water tank of the electrolysis device, the sludge discharge port connected to the sludge discharge pump of the electrolysis device, and the exhaust port connected to the gas collection pipe of the electrolysis device. The generated gas is connected to the exhaust fan of the tail gas absorption device through the gas collection pipe of the electrolysis device. The power supply current intensity of the electrolysis cell is adjusted to 5A-10A according to the SBR product water quality.

[0022] This application also discloses a method for treating nanofiltration concentrate of leachate from an incineration plant, which uses an electrodialysis device to separate inorganic salts in the nanofiltration concentrate into fresh water and concentrated water.

[0023] The fresh water is passed through the nanofiltration membrane in the nanofiltration unit to concentrate and extract high molecular organic matter to the concentrate end. In the nanofiltration unit, inorganic salts are further removed by the reverse osmosis unit before being reused. The concentrate from the electrodialysis unit is removed by the hardness removal unit before entering the evaporation unit.

[0024] The concentrated liquid end of the nanofiltration unit, which is rich in high molecular weight organic matter, first uses an ozone device to oxidize the high molecular weight organic matter into low molecular weight organic matter, thereby improving its biodegradability. Then it enters the SBR unit to remove impurities in the wastewater, including organic matter, ammonia nitrogen, and total phosphorus. Finally, an electrolysis unit is used to further remove impurities, including organic matter, ammonia nitrogen, and total phosphorus, while the wastewater is also absorbed by a tail gas absorption unit.

[0025] In summary, the present invention has the following beneficial effects:

[0026] (1) The present invention utilizes electrodialysis and a hardening removal device to remove hardness from the nanofiltration concentrate of leachate from the incineration plant while concentrating salt content, thereby improving the operational stability of subsequent evaporation and reducing downtime for maintenance and cleaning agent costs.

[0027] (2) This invention utilizes nanofiltration and ozone devices to extract concentrated organic matter, and employs SBR and electrolysis devices to remove organic matter, thus exhibiting the characteristics of high efficiency and stability in treatment effect;

[0028] (3) This invention utilizes a tail gas absorption device to adsorb harmful gases. The adsorbent liquid and the water produced by the hardening device are fed into the evaporation device together. Online gas detectors can be installed at the inlet and outlet of the tail gas absorption tower to detect the emitted gas at all times and prevent harm to the atmospheric environment.

[0029] (4) This invention uses a reverse osmosis device as a guarantee unit to strictly ensure that the produced water meets the standards;

[0030] (5) The present invention utilizes a sludge dewatering device to mix and treat the sludge discharged from the hardening device, SBR device and electrolysis device, and can ensure that the sludge moisture content is less than 75% without adding desludge dewatering agents;

[0031] (6) The method adopted in this invention is highly targeted and completely solves the problem of concentrated water in the nanofiltration device of leachate from waste incineration power plant. It also eliminates the production of membrane concentrate, reduces secondary pollutants, and produces high-quality water with COD, ammonia nitrogen, total nitrogen, total phosphorus, color and other indicators that are superior to the existing national emission standards. It has significant social and environmental benefits. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of a nanofiltration concentrate treatment system for leachate from an incineration plant.

[0033] Figure 2 This is a schematic diagram of an electrodialysis device.

[0034] Figure 3 This is a schematic diagram of a nanofiltration device.

[0035] Figure 4 This is a schematic diagram of a reverse osmosis device.

[0036] Figure 5 This is a schematic diagram of the hardening device.

[0037] Figure 6 This is a schematic diagram of the evaporation device.

[0038] Figure 7 This is a schematic diagram of an ozone generator.

[0039] Figure 8 This is a schematic diagram of the SBR device.

[0040] Figure 9 This is a schematic diagram of the electrolysis device.

[0041] Figure 10 This is a schematic diagram of the exhaust gas absorption device.

[0042] Figure 11 This is a schematic diagram of a sludge dewatering device.

[0043] In the diagram: 1. Raw water tank; 2. Electrodialysis unit feed pump; 3. Precision filter; 4. Electrodialysis unit; 5. Freshwater collection tank; 6. Concentrate collection tank; 7. Electrodialysis unit inlet pipe; 8. First online conductivity meter; 9. Online thermometer; 10. Electrodialysis unit freshwater pipe; 11. Second online conductivity meter; 12. Nanofiltration inlet pump; 13. First security filter; 14. Booster pump; 15. Nanofiltration membrane module; 16. Nanofiltration unit product water tank; 17. Nanofiltration unit concentrate tank; 18. Nanofiltration unit inlet pipe; 19. Third online conductivity meter; 20. Nanofiltration unit freshwater pipe; 21. Fourth online conductivity meter; 22. Reverse osmosis inlet pump; 23. Second security filter; 24. High-pressure pump; 25. Circulation pump; 26. Reverse osmosis... 27. Reverse osmosis membrane module; 28. Reverse osmosis product water tank; 29. ​​Reverse osmosis concentrate tank; 30. Reverse osmosis feed pipe; 31. Fifth online conductivity meter; 32. Return pipe; 33. Reverse osmosis freshwater pipe; 34. Sixth online conductivity meter; 35. Primary reaction tank feed pump; 36. Primary reaction tank; 37. Secondary reaction tank; 38. Thickening tank; 39. Membrane module lift pump; 40. Hardening membrane module; 41. Hardening unit intermediate water tank; 42. Intermediate water pump; 43. Hardening unit product water tank; 44. Hardening unit sludge pump; 45. Primary dosing pipe; 46. Secondary dosing pipe; 47. Primary mixer; 48. First online pH meter; 49. Tertiary dosing pipe; 50. Secondary mixer; 51. Second online pH meter 51. Level gauge; 52. Concentrator mixer; 53. Membrane module outlet pipe; 54. Concentrate pipe; 55. Fourth-stage dosing pipe; 56. Static mixer; 57. Third online pH meter; 58. Evaporator feed pump; 59. Condensate preheater; 60. Non-condensable steam preheater; 61. Circulation pump; 62. Evaporator; 63. Separator; 64. Discharge pump; 65. Mother liquor tank; 66. Condenser; 67. Condensate pump; 68. Condensate collection tank; 69. Compressor; 70. Evaporator inlet pipe; 71. Cooling water inlet; 72. Cooling water return; 73. Steam pipe; 74. Ozone generator feed pump; 75. Ozone generator; 76. Contact reaction tower; 77. Ozone generator product water tank; 78. SBR feed pump; 79. SB R-tank; 80. Aeration blower; 81. SBR sludge pump; 82. SBR product water tank; 83. Decanter; 84. Fourth online pH meter; 85. Online ORP meter; 86. Online dissolved oxygen meter; 87. Electrolysis unit inlet pump; 88. Electrolysis cell; 89. DC power supply; 90. Electrolysis unit product water tank; 91. Electrolysis unit sludge pump; 92. Aeration blower; 93. Electrolysis unit gas collection pipe; 94. Tail gas absorption unit induced draft fan; 95. First-stage tail gas absorption tower; 96. Second-stage tail gas absorption tower; 97. Absorption box; 98. Submersible pump; 99. Filter press feed pump; 100. Filter press; 101. Sludge thickening tank; 102. Waste liquid tank; 103. Waste liquid return pump; 104. Sludge scraper; 105. Flushing water tank;106. Flushing pump; 107. Sludge inlet pipe; 108. Online pressure sensor; 109. Flushing pipe; 110. Online pressure sensor; 111. Sludge thickening tank inlet; 112. Waste liquid return pipe; 113. Sludge. Detailed Implementation

[0044] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. These embodiments do not constitute a limitation of the present invention. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this application.

[0045] A nanofiltration concentrate treatment system for incineration plant leachate, such as Figure 1 As shown, it includes an electrodialysis device to separate inorganic salts from nanofiltration concentrate.

[0046] The desalination end of the electrodialysis unit is connected to the nanofiltration unit to concentrate high-molecular-weight organic matter. The desalination end of the nanofiltration unit is connected to the reverse osmosis unit to further remove inorganic salts, serving as the product water supply unit. The desalination end of the reverse osmosis unit is connected to the product water tank.

[0047] The concentrate end of the electrodialysis unit is connected to the hardening removal unit, which removes calcium and magnesium hardness from the concentrated salts, reducing scaling and clogging in the subsequent evaporation unit. The concentrate end of the nanofiltration unit is connected to the ozone unit, which oxidizes high-molecular-weight organic matter into low-molecular-weight organic matter, increasing the biodegradability of the subsequent SBR unit. The other end of the ozone unit is connected to the SBR unit, removing substances including organic matter, ammonia nitrogen, and total phosphorus from the wastewater. The discharge end of the SBR unit is connected to the electrolysis unit, which further removes organic matter, ammonia nitrogen, and total phosphorus from the SBR unit's permeate. The discharge end of the electrolysis unit is connected to the permeate tank, while the exhaust end is connected to the tail gas absorption unit, which absorbs harmful gases, mainly chlorine, generated during the electrolysis process.

[0048] The drainage ends of the hardening device and the exhaust gas absorption device are connected to the evaporation device. The sludge discharge ends of the hardening device, the SBR device, and the electrolysis device are all connected to the sludge dewatering device for mixing treatment. The sludge from the hardening device, SBR device, and electrolysis device is dewatered to sludge with a moisture content of less than 75%. The clear liquid from the sludge dewatering device is returned to the inlet of the hardening device for reuse. This invention has stable treatment effect, strong targeting, reduces environmental hazards, and effectively improves social and environmental benefits.

[0049] Specifically, the electrodialysis device includes an electrodialysis device raw water tank 1, an electrodialysis module 4, an electrodialysis device fresh water pipe 10, and an electrodialysis device concentrate end. The nanofiltration concentrate of the incineration plant leachate is stored in the raw water tank 1 and then enters the electrodialysis module 4. The electrodialysis device fresh water pipe 10 is connected to the fresh water collection tank 5, and the electrodialysis device concentrate end is connected to the electrodialysis module concentrate collection tank 6.

[0050] The desalination collection tank 5 of the electrodialysis unit is connected to the nanofiltration feed pump 12. The other end of the nanofiltration feed pump 12 is connected to the nanofiltration unit. The nanofiltration unit includes a desalination pipe 20 and a concentrate pipe. The desalination pipe 20 is connected to the product water tank 16 of the nanofiltration unit, and the concentrate pipe is connected to the concentrate tank 17 of the nanofiltration unit.

[0051] The nanofiltration unit's permeate tank 16 is connected to the reverse osmosis feed pump 22, and the other end of the reverse osmosis feed pump 22 is connected to the reverse osmosis unit. The reverse osmosis unit includes a reverse osmosis unit permeate pipe 32 and a reverse osmosis unit concentrate inlet. The reverse osmosis unit permeate pipe 32 is connected to the reverse osmosis unit permeate tank 27, and the reverse osmosis unit concentrate inlet is connected to the electrodialysis unit's raw water tank 1.

[0052] The concentrate collection tank 6 of the electrodialysis unit is connected to the inlet pump 34 of the primary reaction tank. The other end of the inlet pump 34 is connected to the primary reaction tank 35. The primary reaction tank 35 is connected to the filtrate return pipe 112. The effluent from the membrane module of the hardening unit is connected to the permeate tank 42 of the hardening unit via the intermediate water pump 41. The sludge discharge pipes of the primary reaction tank 35, the secondary reaction tank 36, and the thickening tank 37 of the hardening unit are connected to the inlet 111 of the sludge thickening tank.

[0053] Evaporation inlet pump 58 is connected to the hardening device product water tank 42; ozone device inlet pump 74 is connected to the nanofiltration device concentrate tank 17; ozone device product water is connected to the ozone device product water pool 77; SBR device inlet pump 78 is connected to the ozone device product water pool 77; SBR device sludge discharge port is connected to the sludge thickening tank inlet 111; electrolysis device inlet pump 87 is connected to the SBR product water pool 77; electrolysis device outlet is connected to the electrolysis device product water pool 90; electrolysis device sludge discharge port is connected to the sludge thickening tank inlet 111; electrolysis device gas collection pipe 93 is connected to the tail gas absorption device induced draft fan 94; tail gas absorption device submersible pump is connected to the hardening device product water tank 42; sludge thickening tank inlet 111 is connected to the hardening device primary reaction tank 35, secondary reaction tank 36 and thickening tank 37 sludge discharge pipes; SBR device sludge discharge port; electrolysis device sludge discharge port; waste liquid return pipe 112 is connected to the primary reaction tank 35.

[0054] This embodiment also discloses a method for treating nanofiltration concentrate of leachate from an incineration plant, which uses an electrodialysis device to separate inorganic salts in the nanofiltration concentrate into fresh water and concentrated water.

[0055] The fresh water is passed through the nanofiltration membrane in the nanofiltration unit to concentrate and extract high molecular organic matter to the concentrate end. In the nanofiltration unit, inorganic salts are further removed by the reverse osmosis unit before being reused. The concentrate from the electrodialysis unit is removed by the hardness removal unit before entering the evaporation unit.

[0056] The concentrated liquid end of the nanofiltration unit, which is rich in high molecular weight organic matter, first uses an ozone device to oxidize the high molecular weight organic matter into low molecular weight organic matter, thereby improving its biodegradability. Then it enters the SBR unit to remove impurities in the wastewater, including organic matter, ammonia nitrogen, and total phosphorus. Finally, an electrolysis unit is used to further remove impurities, including organic matter, ammonia nitrogen, and total phosphorus, while the wastewater is also absorbed by a tail gas absorption unit.

[0057] like Figure 2 As shown, the electrodialysis device includes a raw water tank 1 and an electrodialysis assembly 4;

[0058] The nanofiltration concentrate of the leachate from the incineration plant is stored in the raw water tank 1. The electrodialysis unit 4 is equipped with an inlet, a concentrate outlet, and a desalination outlet. The inlet of the electrodialysis unit 4 is connected to the inlet pipe 7 of the electrodialysis device, the concentrate outlet is connected to the concentrate collection tank 6, and the desalination outlet is connected to the desalination pipe 10 of the electrodialysis device.

[0059] The inlet pipe 7 of the electrodialysis unit is connected in sequence to the raw water tank 1, the inlet pump 2 of the electrodialysis unit, and the precision filter 3, so as to realize the water supply to the electrodialysis unit 4. In this embodiment, the inlet pipe 7 of the electrodialysis unit is also connected to a first online conductivity meter 8 and an online thermometer 9 located between the inlet pump 2 and the precision filter 3; the fresh water pipe 10 of the electrodialysis device is connected in sequence to a second online conductivity meter 11 and a fresh water collection tank 5.

[0060] The electrodialysis unit first uses a nanofiltration concentrate from the incineration plant leachate to achieve concentration and desalination of the concentrate through anion and cation selective permeable membranes, increasing the overall desalination rate to 60%-80%. The operation is monitored by the first online conductivity meter 8 and online thermometer 9 on the inlet pipe 7 of the electrodialysis unit. In addition to monitoring the operating indicators, the inlet water temperature can also be strictly controlled to prevent damage to the electrodialysis unit.

[0061] like Figure 3 As shown, the nanofiltration device includes a nanofiltration membrane assembly 15; the nanofiltration membrane assembly 15 has an inlet on one side, a concentrate outlet on the other side, and a freshwater outlet at the end. The inlet of the nanofiltration membrane assembly 15 is connected to the inlet pipe 18 of the nanofiltration device, the concentrate outlet is connected to the concentrate tank 17 of the nanofiltration device, and the freshwater outlet is connected to the freshwater pipe 20 of the nanofiltration device.

[0062] The nanofiltration membrane device inlet pipe 18 is sequentially connected to the nanofiltration inlet pump 12, the third online conductivity meter 19, the first security filter 13, and the booster pump 14 to provide water to the nanofiltration membrane module 15. The concentrate port of the nanofiltration membrane module 15 is also connected to the inlet of the first security filter 13 to achieve concentrate circulation. The nanofiltration device desalination pipe 20 is sequentially connected to the fourth online conductivity meter 21 and the nanofiltration device product water tank 16. Because there are many large molecular humic acid substances in the raw water, the nanofiltration membrane device inlet pipe 18 is designed as a flange or union detachable connection to periodically remove and clean the viscous substances accumulated in the pipe.

[0063] The freshwater separated by the electrodialysis unit is used to extract macromolecular humic acid substances through a nanofiltration device, and the separation of a small amount of salt and organic matter is tested. The concentrate from the nanofiltration membrane unit is partially refluxed, and the reflux pipe is connected to the nanofiltration booster pump 14. The operating pressure of the nanofiltration booster pump is between 0.5-1.0 MPa. The nanofiltration membrane is designed with a flux of 8-12 LMH. The raw water is passed through once and the concentrate is circulated to achieve a recovery rate of 90%.

[0064] like Figure 4 As shown, the reverse osmosis device includes a reverse osmosis membrane module 26. One end of the reverse osmosis membrane module 26 has an inlet, the other end has a concentrate outlet, and the other end has a desalination outlet.

[0065] The inlet of the reverse osmosis membrane module 26 is connected to the inlet pipe 29 of the reverse osmosis unit. The inlet pipe 29 of the reverse osmosis unit is connected in sequence to the reverse osmosis feed pump 22, the fifth online conductivity meter 30, the second security filter 23, the high pressure pump 24 and the circulation pump 25.

[0066] The freshwater outlet is connected to the freshwater pipe 32 of the reverse osmosis unit, and the freshwater pipe 32 of the reverse osmosis unit is connected in sequence to the sixth online conductivity meter 33 and the product water tank 27 of the reverse osmosis unit.

[0067] The concentrate outlet is connected to the concentrate tank 28 of the reverse osmosis unit. The other end of the concentrate tank 28 is connected to the raw water tank 1 of the electrodialysis unit. The concentrate outlet is also connected to a branch return pipe 31, and the other end of the return pipe 31 is connected to the inlet of the circulation pump 25.

[0068] The concentrate from the reverse osmosis membrane module is partially recycled. The recycling pipe is connected to the inlet of the reverse osmosis circulation pump 25. The high-pressure pump 24 in the reverse osmosis unit operates at a pressure between 1.0 and 3.0 MPa. The reverse osmosis membrane is designed to have a flux of 18-25 LMH. The design uses a single-pass feed water and concentrate recycling system to achieve a recovery rate of 70-75%.

[0069] like Figure 5 As shown, the hardening device includes a primary reaction tank 35 and a hardening membrane assembly 39;

[0070] The primary reaction tank 35 is connected to the upper side of the primary reaction tank inlet pump 34. The top of the primary reaction tank 35 is connected to the filtrate return pipe 112, the primary dosing pipe 44, the secondary dosing pipe 45, and the first online pH meter 47. The primary reaction tank 35 is equipped with a primary agitator 46. The lower side of the primary reaction tank 35 is connected to the secondary reaction tank 36 through a flow hole.

[0071] The top of the secondary reaction tank 36 is connected to a tertiary dosing pipe 48 and a second online pH meter 50. A secondary agitator 49 is installed inside the secondary reaction tank. The upper part of the secondary reaction tank 36 is connected to a concentration tank 37 through a flow hole.

[0072] The top of the thickening tank 37 is connected to an online float-linkage level gauge 51. The lower side of the thickening tank 37 is connected to a membrane module lift pump 38. The outlet pipe of the membrane module lift pump 38 is connected to the inlet of the de-hardening membrane module 39. The bottom of the primary reaction tank 35, the secondary reaction tank 36, and the thickening tank 37 are connected to a de-hardening device sludge pump 43. The thickening tank 37 is equipped with a thickening tank agitator 52 and a sludge concentration meter. The de-hardening device sludge pump 43, the membrane module lift pump 38, and the de-hardening membrane module 39 are interlocked for start and stop.

[0073] The concentrate end of the hardening membrane module 39 is connected to the concentrate pipe 54 of the membrane module. The other end of the concentrate pipe 54 is connected to the top of the concentration tank 37. The outlet of the hardening membrane module 39 is connected to the outlet pipe 53 of the membrane module. The other end of the outlet pipe 53 is connected to the intermediate water tank 40 of the hardening device. The bottom outlet of the intermediate water tank 40 of the hardening device is connected to the intermediate water pump 41. The outlet pipe of the intermediate water pump 41 is connected in sequence to the four-stage dosing pipe 55, the static mixer 56, the third online pH meter 57, and the permeate tank 42 of the hardening device.

[0074] The design residence time for the primary reaction tank 35, secondary reaction tank 36, and thickening tank 37 is 45-60 minutes. Ferric chloride is added at a concentration of 50-300 mg / L via the primary dosing pipe 44, and calcium hydroxide at a concentration of 2000-6000 mg / L via the secondary dosing pipe 45. The pH in the primary reaction tank 35 is controlled between 10.5 and 10.5 via the first online pH meter 47. Sodium hydroxide is added at a concentration of 200-600 mg / L via the tertiary dosing pipe 48, and the pH in the secondary reaction tank 36 is controlled between 11.0 and 11.5 via the second online pH meter 50. The thickening tank 37 is equipped with a float-and-rod level gauge, which automatically starts and stops the sludge removal device based on the sludge level. The sludge removal membrane module 39 has a filtration accuracy of 50 nm and a design flux of 180-250 LMH. When the sludge concentration in the thickening tank reaches 2%-5%, the sludge removal device's sludge discharge pump 43 is activated for intermittent sludge discharge.

[0075] Every 30-60 minutes of operation, the hard membrane module 39 is backwashed for 5 minutes using the permeate water from the intermediate water tank 40 of the hardening unit to remove the sludge deposited inside the membrane module, which helps to restore flux. The four-stage dosing pipe 55 is designed to add hydrochloric acid at a concentration of 1000-3000 mg / L to maintain the pH of the permeate water tank of the hardening unit between 6.0 and 6.5. The permeate water from the intermediate water tank 40 of the hardening unit is used as flushing and cleaning water instead of permeate water with added hydrochloric acid, which effectively reduces the amount of front-end chemicals used.

[0076] like Figure 6 As shown, the evaporation device includes an evaporation inlet pump 58, an evaporator 62, a discharge pump 64, a condenser 66, a condensate pump 67, a condensate collection tank 68, and a compressor 69.

[0077] Evaporation inlet pump 58 is connected to the product water tank 42 of the hardening device. The outlet end of evaporation inlet pump 58 is sequentially connected to condensate preheater 59 (one branch), non-condensable steam preheater 60 (one branch), and evaporation inlet pipe 70. The inlet of evaporator 62 is connected to evaporation inlet pipe 70.

[0078] The liquid outlet of evaporator 62 is connected to separator 63, the non-condensable steam outlet of evaporator 62 is connected to non-condensable steam preheater 60, the outlet of separator 63 is connected to circulating pump 61, and the outlet end of circulating pump 61 is connected to evaporator water inlet pipe 70; the inlet of discharge pump 64 is connected to the outlet of circulating pump 61, and the outlet of discharge pump 64 is connected to mother liquor tank 65.

[0079] The other branch of the condensate preheater 59 is connected to the outlet of the condensate pump 67 and the condensate collection tank 68 at both ends. The inlet of the condensate pump 67 is connected to the non-condensable steam outlet of the evaporator 62 and the non-condensable steam outlet of the condenser 66. The other branch of the non-condensable steam preheater 60 is connected to the condenser 66 to condense and reuse the non-condensable steam from the evaporator 62. The two branches of the condenser 66 are connected to the cooling water inlet 71 and the cooling water return 72, respectively. The inlet of the compressor 69 is connected to the separator 63, and the outlet is connected to the evaporator 62.

[0080] The evaporation unit uses a plate heat exchanger, which is not only easy to disassemble for internal inspection and mechanical cleaning, but also allows for adjustment of the system's operational stability by increasing the number of heat exchange plates. It adopts low-temperature evaporation, with an evaporation temperature of 70-75℃, which improves the equipment corrosion problem. The evaporator does not use duplex stainless steel, which greatly reduces investment costs. The front-end product water is backflushed with acid to prevent scaling in the evaporation system. No external defoamers or scale inhibitors are added, which improves the quality of the product water.

[0081] like Figure 7 As shown, the ozone device includes an ozone device inlet pump 74, an ozone generator 75, a contact reaction tower 76, and an ozone device product water tank 77. The upper side of the contact reaction tower 76 is provided with an inlet, which is connected to the ozone device inlet pump 74. The other end of the ozone device inlet pump 74 is connected to the nanofiltration device concentrate tank 17. The lower side of the contact reaction tower 76 is provided with an ozone inlet, which is connected to the ozone generator 75 outlet. The lower side of the contact reaction tower 76 is provided with an outlet, which is connected to the ozone device product water tank 77.

[0082] The ozone generator's contact reaction tower 76 is filled with a catalyst. Under the action of the catalyst, strong oxidant hydroxyl radicals are generated, which are non-selective, highly reactive, and fast. The ozone dosage is 2.0-5.0 kg / t, and the designed residence time is not less than 1.5 h.

[0083] like Figure 8As shown, the SBR device includes an SBR inlet pump 78, an SBR tank 79, and an SBR sludge discharge pump 81. The upper part of the SBR tank 79 has an inlet connected to the SBR inlet pump 78, and the other end of the SBR inlet pump 78 is connected to the ozone device product water tank 77. The upper part of the SBR tank 79 has a decanter 83, which is connected to the SBR product water tank 82 via an outlet. The bottom of the SBR tank 79 has an aeration pipeline connected to an aeration blower 80. The middle part of the SBR tank 79 has a sludge discharge port connected to the inlet of the SBR sludge discharge pump 81. The outlet of the SBR sludge discharge pump 81 is connected to the inlet 111 of the sludge thickening tank. The SBR tank 79 is equipped with a fourth online pH meter 84, an online ORP meter 85, and an online dissolved oxygen meter 86.

[0084] This intermittently aerated reaction device completes five stages—influent, aeration, sedimentation, effluent, and settling—in a single tank to degrade pollutants such as organic matter and ammonia nitrogen. During effluent influent, the agitator is activated for stirring. After the anaerobic stage, the aeration fan 80 is activated to supply oxygen to the microorganisms within the device through micropores. After the aerobic stage, the aeration fan is turned off, and the device enters the sedimentation stage. The effluent time of the SBR device is then controlled by the decanter 83 and the liquid level. The dissolved oxygen level during the effluent stage is controlled to be less than 0.5 mg / L by the dissolved oxygen meter in the SBR device, 2.0 mg / L during the aeration stage, and the sludge concentration is 5.0-6.0 g / L.

[0085] like Figure 9 As shown, the electrolysis device includes an electrolysis device inlet pump 87, an electrolysis cell 88, a DC power supply 89, an electrolysis device product water tank 90, an electrolysis device sludge discharge pump 91, and an aeration blower 92. The inlet of the electrolysis cell 88 is connected to the electrolysis device inlet pump 87, and the other end of the electrolysis device inlet pump 87 is connected to the SBR product water tank 82. The outlet of the electrolysis cell 88 is connected to the electrolysis device product water tank 90. ​​The sludge discharge port of the electrolysis cell 88 is connected to the inlet of the electrolysis device sludge discharge pump 91. The outlet of the electrolysis device sludge discharge pump 91 is connected to the inlet 111 of the sludge thickening tank. The electrolysis cell 88 is connected to the electrolysis device gas collection pipe 93, and the gas generated therefrom is connected to the tail gas absorption device induced draft fan 94 through the electrolysis device gas collection pipe 93. An online gas detector is installed near the ground near the electrolysis cell 88.

[0086] The electrolysis unit can adjust the current intensity between 5A and 10A according to the SBR permeate water quality. Within 1 hour, COD removal can reach more than 50%, ammonia nitrogen removal can reach 80%, total nitrogen removal can reach more than 40%, and total phosphorus removal can exceed 90%.

[0087] like Figure 10 As shown, the exhaust gas absorption device includes an exhaust gas absorption device induced draft fan 94, a primary exhaust gas absorption tower 95, a secondary exhaust gas absorption tower 96, an absorption box 97, and a submersible pump 98.

[0088] The outlet of the exhaust fan 94 of the exhaust gas absorption device is connected to the lower part of the primary exhaust gas absorption tower 95. The upper part of the primary exhaust gas absorption tower 95 is connected to the lower part of the secondary exhaust gas absorption tower 96. The top of the primary exhaust gas absorption tower 95, the top of the secondary exhaust gas absorption tower 96, and the top of the secondary exhaust gas absorption tower 96 are connected to the submersible pump 98. The absorbent liquid from the primary exhaust gas absorption tower 95 and the secondary exhaust gas absorption tower 96 enters the absorption tank 97. The absorption tank 97 is connected to the inlet of the submersible pump 98. The outlet of the submersible pump 98 is connected to the primary exhaust gas absorption tower 95, the secondary exhaust gas absorption tower 96, and the water production tank 42 of the hardening device, respectively. After installing an online gas detector at the outlet of the secondary exhaust gas absorption tower 96, it is discharged into the atmosphere.

[0089] The tail gas is absorbed by acid-base neutralization. The part of the submersible pump in contact with the medium is made of corrosion-resistant PP material, which transports the liquid alkali in the absorption tank to the tail gas absorption tower. It is sprayed from top to bottom and comes into contact with the high-efficiency packing material inside, increasing the contact area between the liquid alkali and the gas and extending the contact time. A demister is installed at the top of the tower to remove liquid alkali mist from the tail gas. The two-stage tail gas absorption tower greatly improves the absorption effect. An online gas detector is installed at the outlet of the secondary tail gas absorption tower 96 to improve safety performance. When the concentration of liquid alkali in the absorption tank is too low, the liquid alkali is immediately replaced to maintain its concentration at 20%, and the liquid alkali is transported to the hardening device's product water tank 42 by the submersible pump 98.

[0090] like Figure 11 As shown, the sludge dewatering device includes a filter press 100, a sludge thickening tank 101, a waste liquid tank 102, and a waste liquid return pump 103.

[0091] The sludge inlet of the filter press 100 is connected to the sludge inlet pipe 107. The filter press feed pump 99 and the online pressure sensor 108 are connected in sequence to the sludge inlet pipe 107. The inlet of the filter press feed pump 99 is connected to the sludge thickening tank 101.

[0092] The flushing port of the filter press 100 is connected to the flushing pipe 109, and the flushing water tank 105, the flushing pump 106, and the online pressure sensor 110 are connected in sequence on the flushing pipe 109.

[0093] The filtrate outlet of the filter press 100 is connected to the inlet of the waste liquid tank 102, the inlet of the waste liquid return pump 103 is connected to the waste liquid tank 102, the outlet of the waste liquid return pump 103 is connected to the waste liquid return pipe 112, and is connected to the primary reaction tank 35; the sludge 113 produced by the filter press 100 is transported to the landfill.

[0094] The sludge inlet of the sludge thickening tank 101 is connected to the outlets of the sludge discharge pump 43 of the hardening device, the sludge discharge pump 81 of the SBR device, and the sludge discharge pump 92 of the electrolysis device. Chemical sludge and raw sludge are mixed and treated, eliminating the need for PAM and reducing costs. The sludge thickening tank 101 is equipped with a sludge scraper 104, which scrapes the sludge to the bottom sludge collection tank. The inlet is equipped with a sludge return pipe to the sludge thickening tank 101. The outlet pipe of the flushing pump 106 is connected to the flushing port of the filter press 100. The outlet pipe of the flushing pump 106 is equipped with a flushing return pipe to the flushing water tank 105. The sludge is then transported to the inlet of the filter press 100 by the filter press feed pump 99. After dewatering, the sludge moisture content is less than 75%.

[0095] This invention can effectively separate macromolecular organic matter and total dissolved solids in nanofiltration concentrate of incinerator leachate and remove them through different processes. The pollutants such as COD, ammonia nitrogen, total nitrogen, total hardness and total phosphorus in the effluent are better than the existing national emission standards. No concentrate or harmful gases are generated during the treatment process. The final water can be reused, the sludge can be sent to the incinerator for incineration, and the salt can be recycled. This invention realizes the full-scale treatment of nanofiltration concentrate of leachate from waste incineration plants.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within the scope of its essence and protection. Such modifications or equivalent substitutions should also be considered to fall within the protection scope of the present invention.

Claims

1. A nanofiltration concentrate treatment system for incineration plant leachate, characterized in that: The system includes an electrodialysis unit to separate inorganic salts from the nanofiltration concentrate; a desalination end of the electrodialysis unit is connected to the nanofiltration unit to concentrate high-molecular-weight organic matter; a desalination end of the nanofiltration unit is connected to a reverse osmosis unit to further remove inorganic salts; and a desalination end of the reverse osmosis unit is connected to a product water tank. The concentrate end of the electrodialysis unit is connected to the hardening removal unit to remove total hardness, and the drain end of the hardening removal unit is connected to the evaporation unit; the concentrate end of the nanofiltration unit is connected to the ozone unit to oxidize high molecular organic matter into low molecular organic matter, and the other end of the ozone unit is connected to the SBR unit to remove substances including organic matter, ammonia nitrogen, and total phosphorus in wastewater. The SBR unit's drain end is connected to the electrolysis unit, the electrolysis unit's drain end is connected to the product water tank, and the exhaust end is connected to the tail gas absorption unit, which in turn is connected to the evaporation unit. The sludge discharge ends of the hardening unit, the SBR unit, and the electrolysis unit are all connected to the sludge dewatering unit for mixing treatment. The hardening removal device includes a primary reaction tank and a hardening removal membrane assembly. The top of the primary reaction tank is connected to a primary dosing pipe and a secondary dosing pipe, and the bottom of the primary reaction tank is connected to the secondary reaction tank through a flow passage. The top of the secondary reaction tank is connected to the tertiary dosing pipe; the upper part of the secondary reaction tank is connected to the thickening tank through the flow hole; the lower part of the thickening tank is connected to the membrane module lift pump, and the outlet end of the membrane module lift pump is connected to the inlet end of the hardened membrane module. Ferric chloride is added via the first dosing tube, calcium hydroxide via the second dosing tube, and sodium hydroxide via the third dosing tube. The concentrate from the hard membrane removal module returns to the top of the concentration tank, and the outlet is connected to the intermediate water tank of the hard membrane removal unit. The bottom of the intermediate water tank is connected to the intermediate water pump, and the outlet of the intermediate water pump is connected to the fourth dosing pipe, which adds hydrochloric acid. The outlet of the intermediate water tank of the hard membrane removal unit also serves as the rinsing / cleaning water for the hard membrane removal module.

2. The nanofiltration concentrate treatment system for incineration plant leachate according to claim 1, characterized in that: The evaporation unit includes an evaporation water inlet pump, a compressor, and an evaporator. The inlet of the evaporation water inlet pump is connected to the outlet of the hardening device, and the outlet is connected in sequence to the condensate preheater, the non-condensable steam preheater, and the evaporation water inlet pipe. The two inlets of the evaporator are connected to the evaporation water inlet pipe and the outlet of the compressor, respectively. The inlet of the compressor is connected to the separator. The liquid outlet of the evaporator is connected to the separator, the non-condensable vapor outlet of the evaporator is connected to the non-condensable vapor preheater, the outlet of the separator is connected to the circulating pump, and the outlet of the circulating pump is connected to the evaporator inlet pipe; the non-condensable vapor outlets of the evaporator and the condenser are connected to the condensate pump, and the outlet of the non-condensable vapor preheater is connected to the condenser to condense and reuse the non-condensable vapor from the evaporator.

3. The nanofiltration concentrate treatment system for incineration plant leachate according to claim 1, characterized in that: The ozone device includes an ozone inlet pump, an ozone generator, and a contact reaction tower. The upper side of the contact reaction tower has an inlet connected to the ozone inlet pump. The lower side of the contact reaction tower has an ozone inlet connected to the outlet of the ozone generator. The lower side of the contact reaction tower has an outlet connected to the ozone device's water production tank. The contact reaction tower is filled with a catalyst, with an ozone dosage of 2.0-5.0 kg / t and a designed residence time of not less than 1.5 hours.

4. The nanofiltration concentrate treatment system for incineration plant leachate according to claim 1, characterized in that: The SBR unit has an inlet at the top connected to the SBR feed pump, a decanter at the top connected to the outlet connected to the SBR product water tank, an aeration pipeline at the bottom connected to an aeration blower, a sludge discharge port at the bottom connected to the SBR sludge discharge pump, and the outlet of the SBR sludge discharge pump connected to the sludge thickening tank. When the water is fed in, the agitator is turned on for stirring. After the anaerobic stage, the aeration blower is turned on to supply oxygen to the microorganisms in the device through microporous aeration. After the aerobic stage, the aeration blower is turned off and the sedimentation stage begins. Then, the effluent time of the SBR device is controlled by the decanter and the liquid level. The dissolved oxygen in the SBR device is controlled by the dissolved oxygen meter to be less than 0.5 mg / L in the influent stage, 2.0 mg / L in the aeration stage, and the sludge concentration is 5.0-6.0 g / L.

5. The nanofiltration concentrate treatment system for incineration plant leachate according to claim 1, characterized in that: The electrolysis unit includes an electrolysis cell. The inlet of the electrolysis cell is connected to the feed water pump of the electrolysis unit, the outlet is connected to the product water tank of the electrolysis unit, the sludge discharge port is connected to the sludge discharge pump of the electrolysis unit, and the exhaust port is connected to the gas collection pipe of the electrolysis unit. The generated gas is connected to the exhaust fan of the tail gas absorption device through the gas collection pipe of the electrolysis unit. The power supply current intensity of the electrolysis cell is adjusted to 5A-10A according to the SBR product water quality.

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