A low-carbon multistage membrane distillation bioreactor for treating landfill leachate

Abstract

This invention discloses a low-carbon multi-stage membrane distillation bioreactor for treating landfill leachate, belonging to the field of landfill leachate treatment. It includes a membrane treatment unit, a temperature control unit, a condensation and cooling unit, and a pipeline pump and valve unit. The leachate is pumped into the membrane tank, and the temperature control unit ensures a constant temperature in the membrane tank. Steam generated by the vapor pressure difference across the hydrophobic membrane permeates through the membrane pores and condenses into permeate, thus achieving membrane separation. By switching the pipeline pumps and valves, the multi-stage membrane distillation bioreactor can be flexibly combined in series and parallel operation, thereby further improving the effluent quality. This invention overcomes the shortcomings of single membrane distillation technology, such as membrane fouling due to salt accumulation, low treatment efficiency, unstable permeate quality, and high thermal energy consumption. It has the advantages of high treatment efficiency, good effluent quality, energy self-sufficiency, high methane recovery rate, controllable reactor temperature as needed, and flexible multi-stage switching and combination.

Description

Technical Field

[0001] This invention relates to the field of landfill leachate treatment technology, and in particular to a low-carbon multistage membrane distillation bioreactor for treating landfill leachate. Background Technology

[0002] Landfill leachate from waste treatment plants is a high-concentration organic wastewater produced during the dumping, landfilling, or incineration of waste. It is generated from the moisture contained within the waste itself, external moisture, and the fermentation and decomposition of organic matter. Its composition is extremely complex, and its pollutant content is very high, making treatment extremely difficult and a persistent research challenge. Once landfill leachate seeps into groundwater or surface water, it will cause serious water pollution, significantly impacting aquatic ecosystems and water quality safety.

[0003] Currently, traditional landfill leachate treatment systems often employ a "biological treatment + RO reverse osmosis" process. However, the biological treatment stage typically suffers from low nitrogen removal efficiency, high sludge production, and the need for additional carbon sources. Reverse osmosis (RO) membranes also have issues such as internal salt circulation, frequent membrane fouling, and high energy consumption. In recent years, membrane distillation (MD) technology has gradually become a research hotspot. Although it possesses strong separation capabilities, single-stage membrane distillation technology also faces challenges in treating high-concentration organic wastewater like landfill leachate, including membrane fouling due to salt accumulation, low treatment efficiency, unstable permeate quality, and high thermal energy consumption. Summary of the Invention

[0004] The purpose of this invention is to provide a low-carbon multi-stage membrane distillation bioreactor for treating landfill leachate, which overcomes the disadvantages of single membrane distillation technology, such as membrane fouling due to salt accumulation, low treatment efficiency, unstable effluent quality, and high thermal energy consumption. It has the advantages of high treatment efficiency, good effluent quality, energy self-sufficiency, high methane recovery rate, controllable reactor temperature as needed, and flexible switching and combination of multiple stages.

[0005] To achieve the above objectives, the present invention provides a low-carbon multi-stage membrane distillation bioreactor for treating landfill leachate, comprising: The membrane treatment unit pumps landfill leachate into the membrane tank, where the vapor pressure difference across the hydrophobic membrane generates steam that permeates through the membrane pores and condenses into permeate water, thus achieving membrane separation. Temperature control unit keeps the membrane treatment unit at a constant temperature; The condensation and cooling unit condenses the steam that has passed through the membrane pores into product water; The pipeline pump and valve unit enables the combination of series and parallel operation modes of multi-stage membrane distillation bioreactors through the switching of pipeline pumps and valves.

[0006] Preferably, the membrane treatment unit includes a membrane distillation assembly 1, a membrane tank 1, a constant temperature water tank 1, a membrane distillation assembly 2, a membrane tank 2, a constant temperature water tank 2, a membrane distillation assembly 3, a membrane tank 3, and a constant temperature water tank 3; Membrane tank 1, membrane tank 2, and membrane tank 3 are respectively equipped with membrane distillation module 1, membrane distillation module 2, and membrane distillation module 3. The outside of membrane tank 1, membrane tank 2, and membrane tank 3 are constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3, respectively, to provide constant temperature conditions for membrane tank 1, membrane tank 2, and membrane tank 3. Membrane tank 1, membrane tank 2, and membrane tank 3 are respectively connected to the exhaust pipes of membrane tank 1, membrane tank 2, and membrane tank 3. The exhaust pipes of membrane tank 1, membrane tank 2, and membrane tank 3 are connected to the same pipeline and then connected to the gas storage tank.

[0007] Preferably, the membranes of membrane distillation module one, membrane distillation module two, and membrane distillation module three are all submerged hydrophobic microporous membranes made of polytetrafluoroethylene (PTFE), with a pore size of 0.2 μm and a water contact angle >120°.

[0008] Preferably, the temperature control unit includes a steam heat exchanger, a constant temperature water tank inlet pipe, a constant temperature water tank outlet pipe, a constant temperature water tank inlet pipe, a constant temperature water tank outlet pipe, a constant temperature water tank outlet pipe, a constant temperature water tank outlet pipe, and a constant temperature water tank return water pump. Constant temperature water tanks 1, 2, and 3 are connected to the inlet pipes of constant temperature water tanks 1, 2, and 3 respectively. These inlet pipes are connected to the steam heat exchanger via the same pipe. The constant temperature water tanks 1, 2, and 3 are also connected to the outlet pipes of constant temperature water tanks 1, 2, and 3 respectively. These outlet pipes are connected to the constant temperature water tank return water pump via the same pipe, which is then connected to the steam heat exchanger.

[0009] Preferably, the condensation and cooling unit includes a membrane tank 1 condenser, a membrane tank 1 pressure water production tank, and a membrane tank 1 suction pump connected in sequence, a membrane tank 2 condenser, a membrane tank 2 pressure water production tank, and a membrane tank 2 suction pump connected in sequence, a membrane tank 3 condenser, a membrane tank 3 pressure water production tank, and a membrane tank 3 suction pump connected in sequence, and also includes a cooling tower and a cooling water circulation pump. The membrane tank condenser, membrane tank condenser 2, and membrane tank condenser 3 are respectively connected to the outlet pipes of membrane tank condenser 1, membrane tank condenser 2, and membrane tank condenser 3. The outlet pipes of membrane tank condenser 1, membrane tank condenser 2, and membrane tank condenser 3 are connected to the same pipe and then to the cooling tower. The membrane tank condenser 1, membrane tank 2, and membrane tank condenser 3 are respectively connected to the inlet pipes of membrane tank condenser 1, membrane tank 2, and membrane tank condenser 3. The inlet pipes of membrane tank 1, membrane tank 2, and membrane tank condenser 3 are connected to the same pipe and then to the cooling water circulation pump. The cooling water circulation pump is connected to the cooling tower to form a circulation.

[0010] Preferably, the pipeline pump valve unit includes a membrane tank 1 inlet pipe, a membrane tank 1 outlet pipe, a membrane tank 1 product water pipe, a pipe from the membrane tank 1 product water pipe to the product water tank, a series pipe between membrane tank 1 and membrane tank 2, a parallel pipe between membrane tank 1 and membrane tank 2, a membrane tank 1 return pipe, a membrane tank 2 inlet pipe, a membrane tank 2 outlet pipe, a membrane tank 2 product water pipe, a pipe from the membrane tank 2 product water pipe to the product water tank, a series pipe between membrane tank 2 and membrane tank 3, a parallel pipe between membrane tank 2 and membrane tank 3, a membrane tank 2 return pipe, a membrane tank 3 inlet pipe, a membrane tank 3 outlet pipe, a membrane tank 3 product water pipe, a pipe from the membrane tank 3 product water pipe to the product water tank, and a membrane tank 3 return pipe; Membrane tank 1 is connected to landfill leachate booster pump via membrane tank 1 inlet pipe. Landfill leachate booster pump is connected to landfill leachate storage tank. Landfill leachate storage tank is connected to landfill leachate storage tank inlet pipe and landfill leachate storage tank return pipe. Landfill leachate storage tank inlet pipe is used for the entry of landfill leachate. Membrane tank 1 is connected to membrane tank 2 via a series of interconnected outlet pipes, parallel pipes connecting membrane tank 1 and membrane tank 2, and inlet pipes connecting membrane tank 2. Membrane tank 2 is connected to membrane tank 3 via a series of interconnected outlet pipes, parallel pipes connecting membrane tank 2 and membrane tank 3, and inlet pipes connecting membrane tank 3. Membrane tank 3 is connected to membrane tank 3 via a series of interconnected outlet pipes and return pipes connecting membrane tank 3. The outlet pipe of membrane tank 1 and the parallel pipe between membrane tank 1 and membrane tank 2 are connected by a return pipe of membrane tank 1. The outlet pipe of membrane tank 2 and the parallel pipe between membrane tank 2 and membrane tank 3 are connected by a return pipe of membrane tank 2. The return pipes of membrane tank 1, membrane tank 2, and membrane tank 3 are connected to the same pipe and connected to the return pipe of the landfill leachate storage tank. The parallel pipes between membrane tank 1 and membrane tank 2, and the inlet pipe between membrane tank 2 are connected by a series pipe between membrane tank 1 and membrane tank 2; the parallel pipes between membrane tank 2 and membrane tank 3, and the inlet pipe between membrane tank 3 are connected by a series pipe between membrane tank 2 and membrane tank 3. Membrane tank 1 and membrane tank 2 are connected in series to the suction pump of membrane tank 1 and the pipeline from the product water pipe of membrane tank 1 to the product water tank, respectively. Membrane tank 2 and membrane tank 3 are connected in series to the suction pump of membrane tank 2 and the pipeline from the product water pipe of membrane tank 2 to the product water tank, respectively. The suction pump of membrane tank 3 is connected to the pipeline from the product water pipe of membrane tank 3 to the product water tank. The pipelines from the product water pipes of membrane tank 1 to the product water tank, membrane tank 2 to the product water tank, and membrane tank 3 to the product water tank are connected to the same pipeline and connected to the product water tank. The product water tank is connected to an outlet.

[0011] Preferably, the temperature control process for constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 is as follows: The self-use steam generated during the waste incineration process is transported via steam pipelines to a steam heat exchanger. After heat exchange, low-temperature steam is discharged. The water in the pipelines is heated by the steam heat exchanger and then flows into three constant-temperature water tanks: constant-temperature water tank 1, constant-temperature water tank 2, and constant-temperature water tank 3. Temperature control valves are installed on the constant-temperature water tank 1, constant-temperature water tank 2, and constant-temperature water tank 3 inlet pipes, which are set to operate according to temperature parameters. The temperature regulating valve opening is adjusted to maintain the temperature in membrane tank 1, membrane tank 2, and membrane tank 3 at the set temperature value; at the same time, the water level in constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 is kept constant. The water that has completed heat exchange in constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 is collected through the outlet pipes of constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 and then pressurized by the constant temperature water tank return water pump and circulated to the steam heat exchanger for reheating.

[0012] Preferably, under the action of the saturated vapor pressure difference formed by the temperature difference, membrane distillation module one treats the landfill leachate in membrane tank one, membrane distillation module two treats the landfill leachate in membrane tank two, and membrane distillation module three treats the landfill leachate in membrane tank three; the process of membrane distillation module one treating the landfill leachate is as follows: The constant temperature water tank maintains the landfill leachate in the membrane tank at a set temperature value and has a saturated vapor pressure difference with the product water side of the membrane distillation module. The vapor on the membrane tank side is pushed through the membrane pores of the membrane distillation module by the saturated vapor pressure difference and enters the product water pipe of the membrane tank. The vapor is condensed by the condenser of the membrane tank. The condensed water enters the pressure product water tank of the membrane tank under the suction action of the suction pump of the membrane tank. The process of treating landfill leachate using membrane distillation modules 2 and 3 is the same as that using membrane distillation module 1. The condensation and cooling process of membrane tank condenser 1, membrane tank condenser 2, and membrane tank condenser 3 is as follows: After being cooled by the cooling tower, the water enters the first, second, and third condensers of the membrane tank through the inlet pipes of the first, second, and third condensers, respectively. The first, second, and third condensers rapidly cool the internal steam to form product water. The product water is then collected through the outlet pipes of the first, second, and third condensers and enters the cooling tower for rapid cooling. The cooled water is then pressurized by the cooling water circulation pump and re-enters the pipeline for cyclic condensation and reuse.

[0013] Preferably, the parallel operation of membrane tank one and membrane tank two is as follows: The leachate in the landfill leachate storage tank enters membrane tank one through the inlet pipe of membrane tank one. After treatment by membrane distillation module one, the concentrate enters membrane tank two through the outlet pipe of membrane tank one, the parallel pipeline of membrane tank one and membrane tank two, and the inlet pipe of membrane tank two. The raw water of membrane tank one enters membrane tank two. The two sets of membrane tanks operate in parallel. At this time, the status of pipeline pumps and valves is as follows: at the raw water / concentrate end, the valves on the outlet pipe of membrane tank one and the parallel pipeline of membrane tank one and membrane tank two are open, and the pumps and valves on the return pipe of membrane tank one are closed; at the outlet end, the valves on the pipeline from the product water pipe of membrane tank one to the product water tank are open, and the valves on the series pipeline of membrane tank one and membrane tank two are closed. The process of parallel operation of membrane tank three and membrane tank two is the same as that of parallel operation of membrane tank one and membrane tank two. In the parallel operation, two or three sets of membrane tanks jointly treat landfill leachate to increase the treatment area. The process of membrane tank one and membrane tank two connected in series is as follows: The leachate in the landfill storage tank enters Membrane Tank 1 through the inlet pipe of Membrane Tank 1. After treatment by Membrane Distillation Module 1, the permeate enters the condenser of Membrane Tank 1 through the permeate pipe of Membrane Tank 1 for condensation. Under the suction action of the suction pump of Membrane Tank 1, it enters the pressure permeate tank of Membrane Tank 1, and then enters Membrane Tank 2 through the series pipeline of Membrane Tank 1 and Membrane Tank 2, and the permeate of Membrane Tank 1 enters Membrane Tank 2. The two sets of membrane tanks operate in series. At this time, the status of the pipeline pump valves is: concentrate end, Membrane Tank 1 outlet pipe, Membrane Tank 1... The pump and valve on the return pipe are open, and the valve on the parallel pipe between membrane tank 1 and membrane tank 2 is closed. At the outlet, the valve on the series pipe between membrane tank 1 and membrane tank 2 is open, and the valve on the pipe from the permeate pipe of membrane tank 1 to the permeate tank is closed. The process of the series operation of membrane tank 3 and membrane tank 2 is the same as that of the series operation of membrane tank 1 and membrane tank 2. In the series operation, the latter set of membrane tanks further treats the leachate after the former set of membrane tanks has treated it. In the parallel operation of the three membrane tanks, the permeate from membrane tank 1, membrane tank 2, and membrane tank 3 is collected in the permeate tank after passing through the permeate pipes from membrane tank 1 to the permeate tank, membrane tank 2 to the permeate tank, and membrane tank 3 to the permeate tank. This is the effluent after parallel treatment. At this time, the status of the pipeline pumps and valves is as follows: On the permeate side, the valves on the permeate pipes from membrane tank 1 to the permeate tank, membrane tank 2 to the permeate tank, and membrane tank 3 to the permeate tank are open, while the valves on the series pipes between membrane tank 1 and membrane tank 2, and between membrane tank 2 and membrane tank 3 are closed. On the concentrate side, the pumps and valves on the return pipes of membrane tank 1 and membrane tank 2 are closed, while the pumps and valves on the return pipe of membrane tank 3 are open. In the case of three membrane tanks connected in series, the permeate from membrane tank 1 enters membrane tank 2 for treatment via the series pipeline connecting membrane tank 1 and membrane tank 2. The permeate from membrane tank 2 enters membrane tank 3 for treatment via the series pipeline connecting membrane tank 2 and membrane tank 3. The permeate from membrane tank 3 enters the permeate tank for storage via the permeate pipe from membrane tank 3, which is the effluent after series treatment. At this time, the status of the pipeline pumps and valves is as follows: On the permeate side, the valves on the series pipelines connecting membrane tank 1 and membrane tank 2, the series pipelines connecting membrane tank 2 and membrane tank 3, and the pipeline from the permeate pipe of membrane tank 3 to the permeate tank are open, while the valves on the pipelines from the permeate pipe of membrane tank 1 to the permeate tank and the pipeline from the permeate pipe of membrane tank 2 to the permeate tank are closed. On the concentrate side, the pumps and valves on the return pipes of membrane tank 1, membrane tank 2, and membrane tank 3 are all open.

[0014] Preferably, the low-carbon multi-stage membrane distillation bioreactor for treating landfill leachate is also equipped with a concentrate circulation pipeline, which returns the untreated concentrate from membrane tank 1, membrane tank 2, and membrane tank 3 to the landfill leachate storage tank via pumps and pipelines. Specifically, the concentrate circulation pipeline in the case of the three membrane tanks connected in series is a large circulation, in which the concentrate from membrane tank 1, membrane tank 2, and membrane tank 3 is circulated by a pump on the return pipe of membrane tank 3. The concentrate circulation pipeline in the case of the three membrane tanks connected in parallel is a small circulation, in which the concentrate from membrane tank 1, membrane tank 2, and membrane tank 3 is circulated by pumps on the return pipes of membrane tank 1, membrane tank 2, and membrane tank 3, respectively.

[0015] Therefore, the low-carbon multi-stage membrane distillation bioreactor for treating landfill leachate, which adopts the above-described structure, has the following beneficial effects: 1. The temperature control valve can be adjusted according to the set temperature value to maintain a constant temperature in each membrane tank, which is beneficial to the membrane distillation reaction process and microbial cultivation. 2. By switching pipeline pumps and valves, the series or parallel operation of multi-stage membrane distillation bioreactors can be freely and flexibly combined to meet actual water production needs. 3. Through the concentrate circulation pipeline, the untreated concentrate in each membrane tank is returned to the landfill leachate storage tank by water pumps and pipelines to reduce the accumulation of salt in the concentrate and avoid membrane pore fouling and blockage. 4. The multi-stage membrane distillation bioreactor provided by this invention maintains the membrane tank at medium and high temperature anaerobic digestion conditions, realizing an anaerobic membrane distillation bioreactor. While further improving the effluent quality, it can also collect methane gas generated during the anaerobic biological treatment of landfill leachate. 5. The multi-stage membrane distillation bioreactor provided by this invention is used as a treatment process for landfill leachate in waste incineration plants. All energy used is provided by the waste incineration plant, achieving complete energy self-sufficiency and green, low-carbon operation.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an embodiment of a low-carbon multistage membrane distillation bioreactor for treating landfill leachate according to the present invention.

[0018] In the diagram: 1. Landfill leachate storage tank; 2. Landfill leachate pressurization pump; 3. Landfill leachate storage tank inlet pipe; 4. Landfill leachate storage tank return pipe; 5. Constant temperature water tank return water pump; 6. Steam heat exchanger; 7. High-temperature steam; 8. Low-temperature steam; 9. Product water tank; 10. Outlet pipe; 11. Membrane distillation module one; 12. Membrane tank one; 13. Constant temperature water tank one; 14. Constant temperature water tank one inlet pipe; 15. Constant temperature water tank one outlet pipe; 16. Membrane tank one inlet pipe; 17. Membrane tank one outlet pipe; 18. Membrane tank one product water pipe; 19. Membrane tank one exhaust pipe; 20. Membrane tank one condenser; 21. Membrane tank one pressurized product water. 22. Membrane Tank 1 Suction Pump; 23. Membrane Tank 1 Permeate Pipe to Permeate Tank; 24. Series Pipe Between Membrane Tank 1 and Membrane Tank 2; 25. Condenser Inlet Pipe Between Membrane Tank 1; 26. Condenser Outlet Pipe Between Membrane Tank 1; 27. Parallel Pipe Between Membrane Tank 1 and Membrane Tank 2; 28. Return Pipe Between Membrane Tank 1; 31. Membrane Distillation Module 2; 32. Membrane Tank 2; 33. Constant Temperature Water Tank 2; 34. Inlet Pipe of Constant Temperature Water Tank 2; 35. Outlet Pipe of Constant Temperature Water Tank 2; 36. Inlet Pipe of Membrane Tank 2; 37. Outlet Pipe of Membrane Tank 2; 38. Permeate Pipe of Membrane Tank 2; 39. Exhaust Pipe of Membrane Tank 2; 40. Condenser of Membrane Tank 2; 41. Pressure Permeate Tank of Membrane Tank 2; 42. Suction pump for membrane tank 2; 43. Pipeline from membrane tank 2 to product water tank; 44. Series connection between membrane tank 2 and membrane tank 3; 45. Condenser inlet pipe for membrane tank 2; 46. Condenser outlet pipe for membrane tank 2; 47. Parallel connection between membrane tank 2 and membrane tank 3; 48. Return pipe for membrane tank 2; 51. Membrane distillation module 3; 52. Membrane tank 3; 53. Constant temperature water tank 3; 54. Inlet pipe for constant temperature water tank 3; 55. Outlet pipe for constant temperature water tank 3; 56. Inlet pipe for membrane tank 3; 57. Outlet pipe for membrane tank 3; 58. Product water pipe for membrane tank 3; 59. Vent pipe for membrane tank 3; 60. Condenser for membrane tank 3; 61. Pressure product water tank for membrane tank 3; 62. 63. Membrane tank three-stage suction pump; 64. Membrane tank three-stage product water pipe to product water tank pipe; 65. Membrane tank three-stage condenser inlet pipe; 66. Membrane tank three-stage condenser outlet pipe; 67. Membrane tank three-stage return pipe; 71. Cooling tower; 72. Cooling water circulation pump; 73. Gas storage tank; 81. Garbage truck; 82. Garbage pit; 83. Grab bucket; 84. Incinerator; 85. Waste heat boiler; 86. Flue gas treatment device; 87. Bag filter; 88. Flue gas heater; 89. Chimney; 90. Steam; 91. Steam turbine generator; 92. High-voltage power grid; 93. Transformer; 94. Low-voltage electricity; 95. Landfill leachate; 96. Self-use steam. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0020] It should be noted that the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0021] Similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0023] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] Example: like Figure 1As shown, the present invention discloses a low-carbon multi-stage membrane distillation bioreactor for treating landfill leachate, comprising a membrane treatment unit, a temperature control unit, a condensation and cooling unit, and a pipeline pump and valve unit. Its basic concept is as follows: landfill leachate is pumped into a membrane tank; the temperature control unit ensures a constant temperature in the membrane tank; steam is generated by the vapor pressure difference across the hydrophobic membrane, permeates through the membrane pores, and condenses into permeate water, thus achieving membrane separation; and by switching the pipeline pump and valve, the multi-stage membrane distillation bioreactor can be operated in series or parallel, thereby further improving the quality of the effluent.

[0025] like Figure 1 As shown, leachate 95 is generated during the waste incineration process. The specific process is as follows: garbage truck 81 transports municipal solid waste and unloads it into the waste pool 82 of the waste treatment plant for stacking and fermentation. The garbage is grabbed by grab bucket 83 and sent to incinerator 84 for high-temperature incineration. The high-temperature flue gas and heat enter the waste heat boiler 85 to generate steam 90. The flue gas then enters the flue gas treatment device 86 for treatment and enters the bag filter 87 to remove particulate matter and fly ash. After meeting the standards, it is heated by the flue gas heater 88 and discharged into the atmosphere through the chimney 89. The steam 90 enters the steam turbine generator 91 to generate electricity. The generated high-voltage electricity is directly connected to the high-voltage power grid 92. Part of the electricity is stepped down to low-voltage electricity 94 by transformer 93 for the plant's own use, and part of the steam is used as self-use steam 96 for the plant's own use. Both the waste pool 82 and the incinerator 84 will generate a large amount of leachate 95.

[0026] The membrane treatment unit includes a membrane distillation assembly 11, a membrane tank 12, a constant temperature water tank 13, a membrane distillation assembly 2 31, a membrane tank 2 32, a constant temperature water tank 2 33, a membrane distillation assembly 3 51, a membrane tank 3 52, and a constant temperature water tank 3 53. The temperature control unit includes a steam heat exchanger 6, a constant temperature water tank 1 inlet pipe 14, a constant temperature water tank 1 outlet pipe 15, a constant temperature water tank 2 inlet pipe 34, a constant temperature water tank 2 outlet pipe 35, a constant temperature water tank 3 inlet pipe 54, a constant temperature water tank 3 outlet pipe 55, and a constant temperature water tank return water pump 5. The condensation and cooling unit includes a condenser 20 for membrane tank 1, a pressure water production tank 21 for membrane tank 1, a suction pump 22 for membrane tank 1, a condenser 40 for membrane tank 2, a pressure water production tank 41 for membrane tank 2, a suction pump 42 for membrane tank 2, a condenser 60 for membrane tank 3, a pressure water production tank 61 for membrane tank 3, a suction pump 62 for membrane tank 3, a cooling tower 71, and a cooling water circulation pump 72. The pipeline pump and valve unit includes a membrane tank 1 inlet pipe 16, a membrane tank 1 outlet pipe 17, a membrane tank 1 product water pipe 18, a membrane tank 1 product water pipe to the product water tank 23, a series pipe 24 connecting membrane tank 1 and membrane tank 2, a parallel pipe 27 connecting membrane tank 1 and membrane tank 2, a membrane tank 1 return pipe 28, a membrane tank 2 inlet pipe 36, a membrane tank 2 outlet pipe 37, a membrane tank 2 product water pipe 38, a membrane tank 2 product water pipe to the product water tank 43, a series pipe 44 connecting membrane tank 2 and membrane tank 3, a parallel pipe 47 connecting membrane tank 2 and membrane tank 3, a membrane tank 2 return pipe 48, a membrane tank 3 inlet pipe 56, a membrane tank 3 outlet pipe 57, a membrane tank 3 product water pipe 58, a membrane tank 3 product water pipe to the product water tank 63, and a membrane tank 3 return pipe 67.

[0027] In this embodiment, the leachate 95 generated during the waste incineration process enters the leachate storage tank 1 through the leachate storage tank inlet pipe 3. After being pressurized by the leachate pressurization pump 2, it enters the membrane tank 12 through the membrane tank inlet pipe 16. The membrane tank 12 contains the membrane distillation assembly 11. The leachate storage tank 1 is also connected to the leachate storage tank return pipe 4.

[0028] In this embodiment, the membranes of membrane distillation assembly 11, membrane distillation assembly 2 31, and membrane distillation assembly 3 51 are all submerged hydrophobic microporous membranes made of polytetrafluoroethylene (PTFE), with a pore size of 0.2 μm and a water contact angle >120°.

[0029] In this embodiment, the membrane tank 12, membrane tank 2 32, and membrane tank 3 52 are respectively surrounded by constant temperature water tank 13, constant temperature water tank 2 33, and constant temperature water tank 3 53, which provide relatively constant temperature conditions for membrane tank 12, membrane tank 2 32, and membrane tank 3 52, so as to facilitate the membrane distillation reaction process and microbial culture.

[0030] In this embodiment, the specific process of temperature control for constant temperature water tank 13, constant temperature water tank 23, and constant temperature water tank 353 is as follows: the self-use steam 96 generated during the waste incineration process is transported through the steam pipeline to the steam heat exchanger 6 via high-temperature steam 7. After heat exchange, low-temperature steam 8 is discharged. The water in the pipeline is heated by the steam heat exchanger 6 and then enters constant temperature water tank 13, constant temperature water tank 23, and constant temperature water tank 353 via the constant temperature water tank inlet pipe 14, constant temperature water tank 234, and constant temperature water tank 354. The valves installed on the constant temperature water tank inlet pipe 14, constant temperature water tank 234, and constant temperature water tank 354 are temperature control valves. The valve opening can be adjusted according to the set temperature value to control the water inlet flow and temperature of the water tank, thereby keeping the temperature in membrane tank 12, membrane tank 232, and membrane tank 352 relatively constant near the set temperature value. Meanwhile, the water levels in constant temperature water tank 13, constant temperature water tank 23, and constant temperature water tank 33 are kept constant. The water that has completed heat exchange in the water tanks is collected through the outlet pipes 15, 35, and 55 of constant temperature water tank 1 and 3 and then pressurized by the constant temperature water tank return water pump 5 and circulated to the steam heat exchanger 6 for heating.

[0031] In this embodiment, under the action of the saturated vapor pressure difference formed by the temperature difference, membrane distillation module 11 treats the landfill leachate 95 in membrane tank 12. The specific process of membrane distillation module 11 is as follows: the constant temperature water tank 13 keeps the landfill leachate 95 in membrane tank 12 at a set temperature value, and there is a saturated vapor pressure difference between the leachate 95 and the product water side of membrane distillation module 11. The vapor on the membrane tank 12 side is driven by the saturated vapor pressure difference to pass through the membrane pores of membrane distillation module 11 and enter the product water pipe 18 of membrane tank 1. The vapor is condensed by membrane tank 1 condenser 20. The condensed water enters membrane tank 1 pressure product water tank 21 under the suction action of membrane tank 1 suction pump 22. The specific processes of membrane distillation module 2 31 and membrane distillation module 3 51 are basically the same as those of membrane distillation module 11, but the quality of the treated raw water may not be exactly the same.

[0032] In this embodiment, the specific condensation and cooling process of the membrane tank condenser 20, membrane tank condenser 40, and membrane tank condenser 60 is as follows: After being cooled by the cooling tower 71, the water enters the membrane tank condenser 20, membrane tank condenser 40, and membrane tank condenser 60 through the inlet pipe 25 of the membrane tank condenser 1, the inlet pipe 45 of the membrane tank condenser 20, and the inlet pipe 65 of the membrane tank condenser 3, respectively. The membrane tank condenser 20, membrane tank condenser 40, and membrane tank condenser 60 are spiral condenser tubes, which can quickly cool the steam in the condenser to form water. After passing through the condenser, the water is collected through the outlet pipe 26 of the membrane tank condenser 1, the outlet pipe 46 of the membrane tank condenser 2, and the outlet pipe 66 of the membrane tank condenser 3, and then enters the cooling tower 71 for rapid cooling. The cooled water is then pressurized by the cooling water circulation pump 72 and re-enters the pipeline for cyclic condensation and cooling.

[0033] In this embodiment, the switching of pipeline pumps and valves can achieve a free and flexible combination of series or parallel operation of multi-stage membrane distillation bioreactors to meet actual water production needs.

[0034] In this embodiment, the specific process of the parallel operation of the membrane distillation bioreactor is as follows: the leachate 95 in the landfill leachate storage tank 1 enters the membrane tank 12 through the inlet pipe 16 of the membrane tank 1. After being treated by the membrane distillation module 11, the concentrate enters the membrane tank 22 through the outlet pipe 17 of the membrane tank 1, the parallel pipe 27 connecting the membrane tank 1 and the membrane tank 2, and the inlet pipe 36 of the membrane tank 2. That is, the raw water of the membrane tank 12 enters the membrane tank 22, and the two sets of membrane tanks operate in parallel. At this time, the status of the pipeline pumps and valves is as follows: at the raw water / concentrate end, the valves on the outlet pipe 17 of the membrane tank 1 and the parallel pipe 27 connecting the membrane tank 1 and the membrane tank 2 are open, and the pump and valves on the return pipe 28 of the membrane tank 1 are closed; at the outlet end, the valves on the pipe 23 from the product water pipe of the membrane tank 1 to the product water tank are open, and the valves on the series pipe 24 connecting the membrane tank 1 and the membrane tank 2 are closed. Similarly, membrane tank 3 (52) can also be operated in parallel with membrane tank 2 (32) by turning on and off the corresponding water pumps and valves. In parallel operation, two or three sets of membrane tanks can jointly treat landfill leachate 95, which can increase the treatment area and improve the effluent flow rate.

[0035] In this embodiment, the specific process of the series operation of the membrane distillation bioreactor is as follows: the landfill leachate 95 in the landfill leachate storage tank 1 enters the membrane tank 12 through the inlet pipe 16 of the membrane tank 1. After being treated by the membrane distillation module 11, the permeate enters the membrane tank 1 condenser 20 through the permeate pipe 18 of the membrane tank 1 and is condensed. Under the suction action of the membrane tank 1 suction pump 22, it enters the membrane tank 1 pressure permeate tank 21 and enters the membrane tank 22 through the series pipe 24 of the membrane tank 1 and the inlet pipe 36 of the membrane tank 2. That is, the permeate of the membrane tank 12 enters the membrane tank 22, and the two sets of membrane tanks are operated in series. At this time, the status of the pipeline pumps and valves is as follows: At the concentrate end, the pumps and valves on the outlet pipe 17 and return pipe 28 of membrane tank 1 are open, while the valves on the parallel pipe 27 connecting membrane tank 1 and membrane tank 2 are closed; at the outlet end, the valves on the series pipe 24 connecting membrane tank 1 and membrane tank 2 are open, while the valves on the permeate pipe 23 from membrane tank 1 to the permeate tank are closed. Similarly, membrane tank 3 52 can also be operated in series with membrane tank 2 32 by opening and closing the corresponding pumps and valves. In series operation, the latter membrane tank further treats the leachate 95 treated by the former membrane tank, further improving the treated water quality.

[0036] In this embodiment, under the parallel operation of the three membrane tanks, the permeate from membrane tank 1 (12), membrane tank 2 (32), and membrane tank 3 (52) is collected via the permeate pipe from membrane tank 1 to permeate tank 23, the permeate pipe from membrane tank 2 to permeate tank 43, and the permeate pipe from membrane tank 3 to permeate tank 63, and then enters the permeate tank 9 for storage, which is the effluent after parallel treatment (discharged through the effluent pipe 10). At this time, the status of the pipeline pumps and valves is as follows: On the permeate side, the valves on the permeate pipes from membrane tank 1 to permeate tank 23, membrane tank 2 to permeate tank 43, and membrane tank 3 to permeate tank 63 are open, and the valves on the series pipes 24 (membrane tank 1 and membrane tank 2) and 44 (membrane tank 2 and membrane tank 3) are closed; on the concentrate side, the pumps and valves on the return pipes 28 (membrane tank 1) and 48 (membrane tank 2) are closed, and the pump and valves on the return pipe 67 (membrane tank 3) are open.

[0037] In this embodiment, under the condition of three sets of membrane tanks connected in series, the permeate from membrane tank 12 enters membrane tank 22 for treatment via the series pipe 24 connecting membrane tank 1 and membrane tank 2. The permeate from membrane tank 22 enters membrane tank 32 for treatment via the series pipe 44 connecting membrane tank 2 and membrane tank 3. The permeate from membrane tank 32 enters permeate tank 9 for storage via the permeate pipe 63 connecting permeate pipe 3, which is the effluent after series treatment (discharged through effluent pipe 10). At this time, the status of pipeline pumps and valves is as follows: On the permeate side, the valves on the series pipes 24 connecting membrane tank 1 and membrane tank 2, the series pipes 44 connecting membrane tank 2 and membrane tank 3, and the permeate pipe 63 connecting membrane tank 3 are open; the valves on the permeate pipes 23 connecting membrane tank 1 and membrane tank 2 and the permeate pipe 43 connecting membrane tank 2 are closed. On the concentrate side, the pumps and valves on the return pipes 28 connecting membrane tank 1, 48 connecting membrane tank 2, and 67 connecting membrane tank 3 are all open.

[0038] In this embodiment, to reduce salt accumulation in the concentrate and avoid membrane pore fouling and blockage, a concentrate circulation pipeline is provided. The untreated concentrate from membrane tank 12, membrane tank 232, and membrane tank 352 is returned to the landfill leachate storage tank 1 via a water pump and pipeline. Specifically, the concentrate circulation pipeline in the case of the three membrane tanks connected in series is a large circulation, and the concentrate from membrane tank 12, membrane tank 232, and membrane tank 352 is circulated by a water pump on the return pipe 67 of membrane tank 3. The concentrate circulation pipeline in the case of the three membrane tanks connected in parallel is a small circulation, and the concentrate from membrane tank 12, membrane tank 232, and membrane tank 352 is circulated by water pumps on the return pipe 28 of membrane tank 1, the return pipe 48 of membrane tank 2, and the return pipe 67 of membrane tank 3, respectively.

[0039] In this embodiment, if it is necessary to operate under the conditions of two sets of membrane tanks connected in series, one set of membrane tanks connected in parallel, or two sets of membrane tanks connected in parallel and one set of membrane tanks connected in series, the corresponding water pumps and valves can be turned on and off.

[0040] In this embodiment, there are three sets of membrane tanks: membrane tank 12, membrane tank 2 32, and membrane tank 3 52. If more sets of membrane tanks are needed, they can be combined using the same connection method to achieve the series and parallel operation of the multi-stage membrane distillation bioreactor.

[0041] In this embodiment, membrane tank 12, membrane tank 2 32, and membrane tank 3 52 are all equipped with gas collection. The gas generated by the microbial reaction process in membrane tank 12, membrane tank 2 32, and membrane tank 3 52, as well as the gas of the landfill leachate 95 itself, are collected through the exhaust pipe 19 of membrane tank 1, the exhaust pipe 39 of membrane tank 2, and the exhaust pipe 59 of membrane tank 3, and then enter the gas storage tank 73 for storage.

[0042] In this embodiment, the temperature control valves on the constant temperature water tank inlet pipe 14, constant temperature water tank inlet pipe 34, and constant temperature water tank inlet pipe 54 can keep the temperature in membrane tank 12, membrane tank 2 32, and membrane tank 3 52 relatively constant near different set temperature values ​​according to the needs of biological reaction and membrane distillation reaction conditions in the membrane tank.

[0043] In this embodiment, the temperature difference between the feed water end and the product water end of the membrane distillation module is positively correlated with the membrane product water flux. Experimental results show that when the membrane tank 12 is operated at 65°C by controlling the temperature of the constant temperature water tank 13, the flux of the membrane distillation module 11 is 25% higher than when it is operated at 55°C.

[0044] In this embodiment, the membrane tank is kept in an anaerobic state, and the temperature of the membrane tank is controlled at medium temperature (30~40℃) and high temperature (50~60℃) by a constant temperature water tank to achieve medium and high temperature anaerobic digestion conditions, thereby realizing an anaerobic membrane distillation bioreactor. This further improves the quality of the effluent and can collect the methane gas generated during the anaerobic biological treatment of landfill leachate 95. The experimental results show that, under the parallel operation of the three-stage membrane distillation bioreactor, when membrane tanks 12, 32, and 52 are controlled at 45℃, 55℃, and 65℃ respectively by constant temperature water tanks 1-13, 33-33, and 53 respectively, after stable operation, the COD removal rate of the permeate from membrane distillation modules 1-11, 31-31, and 51 is all above 98%, the ammonia nitrogen removal rates are 92%, 85%, and 88% respectively, the gas production rates are 1.2, 6.2, and 11.3 L gas / L permeate, and the methane content in the permeate is 51%, 60%, and 67% respectively. The treated effluent meets the relevant standards for reclaimed water and can be used for purposes such as cooling water.

[0045] In this embodiment, the multi-stage membrane distillation bioreactor is used as a treatment process for leachate in a waste incineration plant. All energy is provided by the waste incineration process, achieving complete energy self-sufficiency and green, low-carbon operation. Specifically, the membrane distillation process is driven by temperature difference. The membrane tank heats the constant temperature water tank through a steam heat exchanger 6 to maintain a constant temperature. The heat source 7 of the steam heat exchanger 6 comes from the self-used steam 96 generated during the waste incineration process. All water pumps, temperature control valves, valves, etc. in the system are powered by the steam 90 generated by the waste heat boiler 85, which enters the steam turbine generator 91 to generate electricity. The electricity is then stepped down by the transformer 93 to produce low-voltage electricity 94, without the need for additional energy consumption. Except for a small amount of evaporation and leakage, most of the heating water and condensate cooling water are recycled and reused.

[0046] Therefore, the present invention provides a low-carbon multi-stage membrane distillation bioreactor for treating landfill leachate using the above-mentioned structure. While solving the problems of membrane fouling due to salt accumulation, low treatment efficiency, unstable effluent quality, and high thermal energy consumption caused by single membrane distillation technology, it also provides a method and apparatus for treating landfill leachate with high treatment efficiency, good effluent quality, energy self-sufficiency, high methane recovery rate, and the ability to control reactor temperature as needed and to freely and flexibly switch between multiple stages. It has great potential in landfill leachate treatment and resource utilization.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A low-carbon multi-stage membrane distillation bioreactor for treating landfill leachate, characterized in that, include: The membrane treatment unit pumps landfill leachate into the membrane tank, where the vapor pressure difference across the hydrophobic membrane generates steam that permeates through the membrane pores and condenses into permeate water, thus achieving membrane separation. Temperature control unit keeps the membrane treatment unit at a constant temperature; The condensation and cooling unit condenses the steam that has passed through the membrane pores into product water; The pipeline pump and valve unit enables the combination of series and parallel operation modes of multi-stage membrane distillation bioreactors through the switching of pipeline pumps and valves; The membrane treatment unit includes membrane distillation module 1, membrane tank 1, constant temperature water tank 1, membrane distillation module 2, membrane tank 2, constant temperature water tank 2, membrane distillation module 3, membrane tank 3, and constant temperature water tank 3; Membrane tank 1, membrane tank 2, and membrane tank 3 are respectively equipped with membrane distillation module 1, membrane distillation module 2, and membrane distillation module 3. The outside of membrane tank 1, membrane tank 2, and membrane tank 3 are constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3, respectively, to provide constant temperature conditions for membrane tank 1, membrane tank 2, and membrane tank 3. Membrane tank 1, membrane tank 2, and membrane tank 3 are respectively connected to the exhaust pipes of membrane tank 1, membrane tank 2, and membrane tank 3. The exhaust pipes of membrane tank 1, membrane tank 2, and membrane tank 3 are connected to the same pipe and then connected to the gas storage tank. The temperature control unit includes a steam heat exchanger, a constant temperature water tank inlet pipe, a constant temperature water tank outlet pipe, a constant temperature water tank inlet pipe, a constant temperature water tank outlet pipe, a constant temperature water tank outlet pipe, a constant temperature water tank inlet pipe, a constant temperature water tank outlet pipe, and a constant temperature water tank return water pump. Constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 are respectively connected to the inlet pipes of constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3. The inlet pipes of constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 are connected to the steam heat exchanger through the same pipe. Constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 are respectively connected to the outlet pipes of constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3. The outlet pipes of constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 are connected to the constant temperature water tank return water pump through the same pipe. The constant temperature water tank return water pump is connected to the steam heat exchanger. The condensation and cooling unit includes a condenser in membrane tank 1, a pressure water production tank in membrane tank 1, and a suction pump in membrane tank 1 connected in sequence; a condenser in membrane tank 2, a pressure water production tank in membrane tank 2, and a suction pump in membrane tank 2 connected in sequence; a condenser in membrane tank 3, a pressure water production tank in membrane tank 3, and a suction pump in membrane tank 3 connected in sequence; and also includes a cooling tower and a cooling water circulation pump. The membrane tank condenser, membrane tank condenser 2, and membrane tank condenser 3 are respectively connected to the outlet pipes of membrane tank condenser 1, membrane tank condenser 2, and membrane tank condenser 3. The outlet pipes of membrane tank condenser 1, membrane tank condenser 2, and membrane tank condenser 3 are connected to the same pipe and then to the cooling tower. The membrane tank condenser 1, membrane tank condenser 2, and membrane tank condenser 3 are respectively connected to the inlet pipes of membrane tank condenser 1, membrane tank condenser 2, and membrane tank condenser 3. The inlet pipes of membrane tank condenser 1, membrane tank condenser 2, and membrane tank condenser 3 are connected to the same pipe and then to the cooling water circulation pump. The cooling water circulation pump is connected to the cooling tower to form a circulation. The pipeline pump and valve unit includes: membrane tank 1 inlet pipe, membrane tank 1 outlet pipe, membrane tank 1 product water pipe, membrane tank 1 product water pipe to product water tank, membrane tank 1 and membrane tank 2 in series, membrane tank 1 and membrane tank 2 in parallel, membrane tank 1 return pipe, membrane tank 2 inlet pipe, membrane tank 2 outlet pipe, membrane tank 2 product water pipe, membrane tank 2 product water pipe to product water tank, membrane tank 2 and membrane tank 3 in series, membrane tank 2 and membrane tank 3 in parallel, membrane tank 2 return pipe, membrane tank 3 inlet pipe, membrane tank 3 outlet pipe, membrane tank 3 product water pipe, membrane tank 3 product water pipe to product water tank, and membrane tank 3 return pipe; Membrane tank 1 is connected to landfill leachate booster pump via membrane tank 1 inlet pipe. Landfill leachate booster pump is connected to landfill leachate storage tank. Landfill leachate storage tank is connected to landfill leachate storage tank inlet pipe and landfill leachate storage tank return pipe. Landfill leachate storage tank inlet pipe is used for the entry of landfill leachate. Membrane tank 1 is connected to membrane tank 2 via a series of interconnected outlet pipes, parallel pipes connecting membrane tank 1 and membrane tank 2, and inlet pipes connecting membrane tank 2. Membrane tank 2 is connected to membrane tank 3 via a series of interconnected outlet pipes, parallel pipes connecting membrane tank 2 and membrane tank 3, and inlet pipes connecting membrane tank 3. Membrane tank 3 is connected to membrane tank 3 via a series of interconnected outlet pipes and return pipes connecting membrane tank 3. The outlet pipe of membrane tank 1 and the parallel pipe between membrane tank 1 and membrane tank 2 are connected by a return pipe of membrane tank 1. The outlet pipe of membrane tank 2 and the parallel pipe between membrane tank 2 and membrane tank 3 are connected by a return pipe of membrane tank 2. The return pipes of membrane tank 1, membrane tank 2, and membrane tank 3 are connected to the same pipe and connected to the return pipe of the landfill leachate storage tank. The parallel pipes between membrane tank 1 and membrane tank 2, and the inlet pipe between membrane tank 2 are connected by a series pipe between membrane tank 1 and membrane tank 2; the parallel pipes between membrane tank 2 and membrane tank 3, and the inlet pipe between membrane tank 3 are connected by a series pipe between membrane tank 2 and membrane tank 3. The series pipes of membrane tank 1 and membrane tank 2 are respectively connected to the suction pump of membrane tank 1 and the pipeline from the product water pipe of membrane tank 1 to the product water tank. The series pipes of membrane tank 2 and membrane tank 3 are respectively connected to the suction pump of membrane tank 2 and the pipeline from the product water pipe of membrane tank 2 to the product water tank. The suction pump of membrane tank 3 is connected to the pipeline from the product water pipe of membrane tank 3 to the product water tank. The pipelines from the product water pipe of membrane tank 1 to the product water tank, the pipelines from the product water pipe of membrane tank 2 to the product water tank, and the pipelines from the product water pipe of membrane tank 3 to the product water tank are connected to the same pipeline and connected to the product water tank. The product water tank is connected to an outlet. The temperature control process for constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 is as follows: The self-use steam generated during the waste incineration process is transported via steam pipelines to a steam heat exchanger. After heat exchange, low-temperature steam is discharged. The water in the pipelines is heated by the steam heat exchanger and then flows into three constant-temperature water tanks: constant-temperature water tank 1, constant-temperature water tank 2, and constant-temperature water tank 3. Temperature control valves are installed on the constant-temperature water tank 1, constant-temperature water tank 2, and constant-temperature water tank 3 inlet pipes, which are set to operate according to temperature parameters. The temperature regulating valve opening is adjusted to maintain the temperature in membrane tank 1, membrane tank 2, and membrane tank 3 at the set temperature value; at the same time, the water level in constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 is kept constant. The water that has completed heat exchange in constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 is collected through the outlet pipes of constant temperature water tank 1, constant temperature water tank 2, and constant temperature water tank 3 and then pressurized by the constant temperature water tank return water pump and circulated to the steam heat exchanger for reheating. Under the influence of the saturated vapor pressure difference created by the temperature difference, membrane distillation module one treats the landfill leachate in membrane tank one, membrane distillation module two treats the landfill leachate in membrane tank two, and membrane distillation module three treats the landfill leachate in membrane tank three; the process of membrane distillation module one treating the landfill leachate is as follows: The constant temperature water tank maintains the landfill leachate in the membrane tank at a set temperature value and has a saturated vapor pressure difference with the product water side of the membrane distillation module. The vapor on the membrane tank side is pushed through the membrane pores of the membrane distillation module by the saturated vapor pressure difference and enters the product water pipe of the membrane tank. The vapor is condensed by the condenser of the membrane tank. The condensed water enters the pressure product water tank of the membrane tank under the suction action of the suction pump of the membrane tank. The process of treating landfill leachate using membrane distillation modules 2 and 3 is the same as that using membrane distillation module 1. The condensation and cooling process of membrane tank condenser 1, membrane tank condenser 2, and membrane tank condenser 3 is as follows: After being cooled by the cooling tower, the water enters the first, second, and third condensers of the membrane tank through the inlet pipes of the first, second, and third condensers, respectively. The first, second, and third condensers rapidly cool the internal steam to form product water. The product water is then collected through the outlet pipes of the first, second, and third condensers and enters the cooling tower for rapid cooling. The cooled water is then pressurized by the cooling water circulation pump and re-enters the pipeline for cyclic condensation and cooling for reuse. The parallel operation of membrane tank one and membrane tank two is as follows: The leachate in the landfill leachate storage tank enters membrane tank one through the inlet pipe of membrane tank one. After treatment by membrane distillation module one, the concentrate enters membrane tank two through the outlet pipe of membrane tank one, the parallel pipeline of membrane tank one and membrane tank two, and the inlet pipe of membrane tank two. The raw water of membrane tank one enters membrane tank two. The two sets of membrane tanks operate in parallel. At this time, the status of pipeline pumps and valves is as follows: at the raw water / concentrate end, the valves on the outlet pipe of membrane tank one and the parallel pipeline of membrane tank one and membrane tank two are open, and the pumps and valves on the return pipe of membrane tank one are closed; at the outlet end, the valves on the pipeline from the product water pipe of membrane tank one to the product water tank are open, and the valves on the series pipeline of membrane tank one and membrane tank two are closed. The process of parallel operation of membrane tank three and membrane tank two is the same as that of parallel operation of membrane tank one and membrane tank two. In the parallel operation, two or three sets of membrane tanks jointly treat landfill leachate to increase the treatment area. The process of membrane tank one and membrane tank two operating in series is as follows: The leachate in the landfill storage tank enters Membrane Tank 1 through the inlet pipe of Membrane Tank 1. After treatment by Membrane Distillation Module 1, the permeate enters the condenser of Membrane Tank 1 through the permeate pipe of Membrane Tank 1 for condensation. Under the suction action of the suction pump of Membrane Tank 1, it enters the pressure permeate tank of Membrane Tank 1, and then enters Membrane Tank 2 through the series pipeline of Membrane Tank 1 and Membrane Tank 2, and the permeate of Membrane Tank 1 enters Membrane Tank 2. The two sets of membrane tanks operate in series. At this time, the status of the pipeline pump valves is: concentrate end, Membrane Tank 1 outlet pipe, Membrane Tank 1... The pump and valve on the return pipe are open, and the valve on the parallel pipe between membrane tank 1 and membrane tank 2 is closed. At the outlet, the valve on the series pipe between membrane tank 1 and membrane tank 2 is open, and the valve on the pipe from the permeate pipe of membrane tank 1 to the permeate tank is closed. The process of the series operation of membrane tank 3 and membrane tank 2 is the same as that of the series operation of membrane tank 1 and membrane tank 2. In the series operation, the latter set of membrane tanks further treats the leachate after the former set of membrane tanks has treated it. In the parallel operation of the three membrane tanks, the permeate from membrane tank 1, membrane tank 2, and membrane tank 3 is collected in the permeate tank after passing through the permeate pipes from membrane tank 1 to the permeate tank, membrane tank 2 to the permeate tank, and membrane tank 3 to the permeate tank. This is the effluent after parallel treatment. At this time, the status of the pipeline pumps and valves is as follows: On the permeate side, the valves on the permeate pipes from membrane tank 1 to the permeate tank, membrane tank 2 to the permeate tank, and membrane tank 3 to the permeate tank are open, while the valves on the series pipes between membrane tank 1 and membrane tank 2, and between membrane tank 2 and membrane tank 3 are closed. On the concentrate side, the pumps and valves on the return pipes of membrane tank 1 and membrane tank 2 are closed, while the pumps and valves on the return pipe of membrane tank 3 are open. In the three-membrane tank series operation, the permeate from membrane tank 1 enters membrane tank 2 for treatment via a series pipeline connecting membrane tank 1 and membrane tank 2. The permeate from membrane tank 2 enters membrane tank 3 for treatment via a series pipeline connecting membrane tank 2 and membrane tank 3. The permeate from membrane tank 3 enters the permeate tank for storage via a permeate pipe from membrane tank 3, which is the effluent after series treatment. At this time, the status of the pipeline pumps and valves is as follows: On the permeate side, the valves on the series pipelines connecting membrane tank 1 and membrane tank 2, the series pipeline connecting membrane tank 2 and membrane tank 3, and the pipeline from the permeate pipe of membrane tank 3 to the permeate tank are open; the valves on the pipelines from the permeate pipe of membrane tank 1 to the permeate tank and the pipeline from the permeate pipe of membrane tank 2 to the permeate tank are closed. On the concentrate side, the pumps and valves on the return pipes of membrane tank 1, membrane tank 2, and membrane tank 3 are all open. The low-carbon multi-stage membrane distillation bioreactor for treating landfill leachate is also equipped with a concentrate circulation pipeline. The untreated concentrate from membrane tank 1, membrane tank 2, and membrane tank 3 is returned to the landfill leachate storage tank through pumps and pipelines. In the case of the three membrane tanks connected in series, the concentrate circulation pipeline is a large circulation, and the concentrate from membrane tank 1, membrane tank 2, and membrane tank 3 is circulated by the pump on the return pipe of membrane tank 3. In the case of the three membrane tanks connected in parallel, the concentrate circulation pipeline is a small circulation, and the concentrate from membrane tank 1, membrane tank 2, and membrane tank 3 is circulated by the pumps on the return pipes of membrane tank 1, membrane tank 2, and membrane tank 3, respectively.

2. The low-carbon multi-stage membrane distillation bioreactor for treating landfill leachate as described in claim 1, characterized in that: The membranes in membrane distillation module 1, membrane distillation module 2, and membrane distillation module 3 are all submerged hydrophobic microporous membranes made of polytetrafluoroethylene (PTFE), with a pore size of 0.2 μm and a water contact angle >120°.

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