Underground pipe drainage recycling system for saline-alkali soil improvement

Abstract

The concealed pipe drainage recycling system comprises a water collecting pipeline buried under soil and a vertical shaft, one end of the water collecting pipeline is connected with a sealing cover, the other end of the water collecting pipeline extends into the vertical shaft and is connected with a first three-way electromagnetic valve, and the water collecting pipeline located on the outer side of the vertical shaft is connected with a plurality of water suction pipelines. The plurality of water absorption pipelines are symmetrically distributed along the axial direction of the water collection pipeline; one end of the first three-way electromagnetic valve is connected with a blow-off pipeline, the other end of the first three-way electromagnetic valve is provided with a microbial desalination battery anode chamber, a filtering device is arranged below the microbial desalination battery anode chamber, a lifting pump is arranged at the bottom of the vertical shaft, one end of the lifting pump is communicated with a reservoir through a pipeline, and a recycling pump is arranged in the reservoir and connected with a recycling pipeline; and the other end of the recycling pipeline penetrates out of the soil. Pollutants such as nitrogen and phosphorus in discharged water are purified, and the treated water is uniformly collected and recycled.

Description

Technical Field

[0001] The invention belongs to the technical field of saline-alkali land improvement, and in particular relates to a concealed pipe drainage recycling system for saline-alkali land improvement. Background Art

[0002] As a potential exploitable land resource, saline-alkali land covers a large area and is widely distributed. Since the 1950s and 1960s, domestic researchers have begun to improve salinized soil, mainly using four major measures: physical, water, chemical and biological.

[0003] As one of the important types of water conservancy improvement measures, concealed pipe drainage technology has developed rapidly in recent years, and has made great progress in materials, layout and installation. Initially, concealed pipe drainage technology was mainly used to drain water from low-lying farmland. The infiltration effect allowed the water in the soil to enter the pipe system, thereby lowering the groundwater level and improving the aeration of the farmland.

[0004] As the understanding of the causes of soil salinization gradually deepens, researchers have found that the accumulation of salt in the soil is mainly through the evaporation of groundwater and the evaporation and concentration of surface water. By lowering the groundwater level and reducing the rise of capillary water, the migration of salt to the surface can be effectively inhibited. Concealed pipe drainage technology has also been gradually applied to the improvement of saline-alkali land. Through irrigation, the salt in the soil is dissolved, and the drainage effect is used to make "salt go with water", reducing the accumulation of salt in farmland soil. However, while the concealed pipe drainage technology effectively promotes the direct output of soil water and salt, it also consumes a large amount of agricultural irrigation water resources and reduces water utilization efficiency. The nitrogen, phosphorus and other substances carried by the drainage also cause certain pollution to the receiving water body, which is not conducive to the establishment of water-saving agriculture and the sustainable development of the ecological environment. Therefore, taking into account the improvement of saline-alkali land, ecological and environmental protection, drainage reuse and water-saving irrigation are issues that urgently need to be paid attention to and solved in the current management of saline-alkali land. Summary of the invention

[0005] The purpose of the present invention is to provide a concealed pipe drainage recycling system for improving saline-alkali land, purify pollutants such as nitrogen and phosphorus in drainage, and collect and reuse the treated water in a unified manner.

[0006] The technical solution adopted by the present invention is a concealed pipe drainage recycling system for improving saline-alkali land, comprising a water collection pipe and a vertical shaft buried under the soil, one end of the water collection pipe is connected to a sealing cover, the other end extends into the vertical shaft and is connected to a first three-way solenoid valve, and the water collection pipe located outside the vertical shaft is connected to a plurality of water suction pipes, and the plurality of water suction pipes are symmetrically distributed along the axis of the water collection pipe; One end of the first three-way solenoid valve is connected to a sewage pipe, and the other end is provided with an anode chamber of a microbial desalination battery. The anode chamber of the microbial desalination battery adopts Shewanella and Halophilic Bacteria as anode microorganisms. A filtering device is arranged below the anode chamber of the microbial desalination battery, and a lifting pump is arranged at the bottom of the vertical shaft. One end of the lifting pump is connected to a water reservoir through a pipeline. A reuse pump is arranged in the water reservoir. The reuse pump is connected to a reuse pipeline, and the other end of the reuse pipeline passes through the soil.

[0007] The present invention is also characterized in that The filter device includes a coarse filter layer, a medium filter layer and a fine filter layer from top to bottom. The coarse filter layer is activated carbon, the medium filter layer is quartz stone, and the fine filter layer is crushed stone. The particle sizes of the filter materials in the coarse filter layer, the medium filter layer and the fine filter layer decrease step by step. A microbial desalination battery cation exchange membrane is arranged on the surface of the coarse filter layer, a microbial desalination battery anion exchange membrane is arranged on the surface of the medium filter layer, and a microbial desalination battery cathode chamber is arranged on the surface of the fine filter layer. The microbial desalination battery cathode chamber uses denitrifying Paracoccus and polyphosphate bacteria as cathode microorganisms.

[0008] The recycling pump is connected to a second three-way solenoid valve through a pipeline. One end of the second three-way solenoid valve is connected to the recycling pipeline, and the other end is connected to a flushing pipeline. The flushing pipeline is connected to one end of a plurality of water suction pipelines.

[0009] A first solenoid valve is provided at the connection position between the flushing pipeline and each water absorption pipeline.

[0010] The water absorption pipe is made of polyethylene double-wall corrugated material, the outer wall of the water absorption pipe is corrugated, a number of water inlet holes are opened on the water absorption pipe, a composite filter layer is arranged in the water inlet holes, and the outer wall of the water absorption pipe is wrapped with a permeable membrane and a geotextile from the inside to the outside.

[0011] The inner wall of the water suction pipe is coated with an anti-stick coating.

[0012] The composite filter layer includes sand and gravel, and the sand and gravel are wrapped by geotextile to form a composite filter layer.

[0013] A second solenoid valve is arranged on the connecting pipeline between the lift pump and the water reservoir.

[0014] A water level monitor is provided near the top of the shaft.

[0015] It also includes photovoltaic power generation equipment, which is connected to the lifting pump, the first solenoid valve, the second solenoid valve, the first three-way solenoid valve, the second three-way solenoid valve, the water level monitor and the recycling pump through lines.

[0016] The beneficial effects of the present invention are: (1) The blind pipe drainage recycling system for improving saline-alkali land of the present invention utilizes the metabolic process of microorganisms in the anode chamber of the microbial desalination cell to generate electrons to achieve energy conversion and salt separation. At the same time, microorganisms for denitrification and phosphorus removal are attached to the cathode chamber of the microbial desalination cell to purify the water quality, reduce the salt concentration and remove pollutants such as nitrogen and phosphorus; the microbial metabolism generates electricity to reduce energy consumption and replaces traditional chemical agents, thereby reducing the generation of other pollutants.

[0017] (2) The water reservoir in the concealed pipe drainage recycling system for improving saline-alkali land of the present invention is a device that is easy to install, has a stable structure, and has a long service life. It can be flexibly adjusted according to specific needs. The water reservoir is used to collect the purified drainage, and the allocation of water resources is rationally planned to avoid waste caused by direct discharge. In addition, it is equipped with a reuse system, and the collected water can be reused for irrigation, thereby improving the utilization rate of water resources and achieving the concept of water-saving agriculture.

[0018] (3) The concealed pipe drainage recycling system for saline-alkali land improvement of the present invention uses renewable photovoltaic power generation equipment to provide energy for the entire device. Light energy, as a clean energy source, is beneficial to environmental protection, saves part of the power generation cost, and promotes the economic benefits of the production process. In addition, each device is an electronic system that can automatically monitor and control each device, greatly reducing labor costs, making the operation more refined, and achieving efficient drainage of farmland. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the concealed pipe drainage recycling system for improving saline-alkali land according to the present invention; Figure 2 It is a schematic diagram of the connection of concealed pipes in the concealed pipe drainage recycling system for improving saline-alkali land according to the present invention; Figure 3 The present invention is a schematic diagram of the structure of a water absorption pipe in a concealed pipe drainage recycling system for improving saline-alkali land.

[0020] In the figure, 1. photovoltaic power generation equipment, 2. water collection pipe, 3. permeable membrane, 4. geotextile, 5. water absorption pipe, 6. water inlet, 7. flushing pipe, 8. lifting pump, 9. anode chamber of microbial desalination battery, 10. cation exchange membrane of microbial desalination battery, 11. anion exchange membrane of microbial desalination battery, 12. cathode chamber of microbial desalination battery, 13. composite reverse filtration layer, 14. first solenoid valve, 15. second solenoid valve, 16. first three-way solenoid valve, 17. second three-way solenoid valve, 18. filtering device, 19. vertical shaft, 20. water level monitor, 21. sewage pipe, 22. reservoir, 23. reuse pump, 24. reuse pipe. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0022] Example 1 The present invention is used for a concealed pipe drainage recycling system for improving saline-alkali land, such as Figure 1 As shown, it includes a water collection pipe 2 and a vertical shaft 19 buried under the soil. One end of the water collection pipe 2 is connected to a sealing cover, and the other end extends into the vertical shaft 19 and is connected to a first three-way solenoid valve 16. The water collection pipe 2 located outside the vertical shaft 19 is connected to a plurality of water suction pipes 5, and the plurality of water suction pipes 5 are symmetrically distributed along the axial direction of the water collection pipe 2.

[0023] That is, groundwater is introduced into the system through the water suction pipe 5 and then gathered into the water collection pipe 2. The collected groundwater is uniformly transported to the interior of the vertical shaft 19 through the water collection pipe 2.

[0024] One end of the first three-way solenoid valve 16 is connected to a sewage pipe 21, and the other end is provided with a microbial desalination battery anode chamber 9, a filtering device 18 is provided below the microbial desalination battery anode chamber 9, a lifting pump 8 is provided at the bottom of the vertical shaft 19, one end of the lifting pump 8 is connected to a water reservoir 22 through a pipeline, a recycling pump 23 is provided in the water reservoir 22, the recycling pump 23 is connected to a recycling pipe 24, and the other end of the recycling pipe 24 passes through the soil.

[0025] Furthermore, the filter device 18 includes a coarse filter layer, a medium filter layer and a fine filter layer from top to bottom, the coarse filter layer is activated carbon, the medium filter layer is quartz stone, and the fine filter layer is crushed stone, and the particle sizes of the filter materials in the coarse filter layer, the medium filter layer and the fine filter layer decrease step by step; A microbial desalination cell cation exchange membrane 10 is arranged on the surface of the coarse filter layer, and a microbial desalination cell anion exchange membrane 11 is arranged on the surface of the filter material of the medium filter layer, forming a desalination chamber; a microbial desalination cell cathode chamber 12 is arranged on the surface of the filter material of the fine filter layer.

[0026] Preferably, the microbial desalination cell cation exchange membrane 10 adopts the Shanghai Resin Research Institute (SRI) membrane, and the microbial desalination cell anion exchange membrane 11 adopts the aerospace chemical membrane material AEM-300 membrane.

[0027] The present invention utilizes the metabolic process of microorganisms in the anode chamber of the microbial desalination battery to generate electrons to achieve energy conversion and salt separation. At the same time, microorganisms for denitrification and dephosphorization are attached to the cathode chamber 12 of the microbial desalination battery to purify the water quality, reduce the salt concentration and remove pollutants such as nitrogen and phosphorus; microbial metabolism generates electricity to reduce energy consumption, replaces traditional chemical agents, and reduces the generation of other pollutants.

[0028] Example 2 The present invention is used for a concealed pipe drainage recycling system for improving saline-alkali land, such as Figure 1 As shown, it includes a water collection pipe 2 and a vertical shaft 19 buried under the soil. One end of the water collection pipe 2 is connected to a sealing cover, and the other end extends into the vertical shaft 19 and is connected to a first three-way solenoid valve 16. The water collection pipe 2 located outside the vertical shaft 19 is connected to a plurality of water suction pipes 5, and the plurality of water suction pipes 5 are symmetrically distributed along the axial direction of the water collection pipe 2.

[0029] Furthermore, the water suction pipe 5 and the water collection pipe 2 are arranged according to a certain slope, which is conducive to the timely flow and collection of drainage under the action of gravity.

[0030] One end of the first three-way solenoid valve 16 is connected to a sewage pipe 21, which receives sewage from the inner wall of the water suction pipe 5 and the water collection pipe 2, or directly discharges the sewage into a drainage ditch or other water receiving body when the water level in the shaft 19 is too high.

[0031] A microbial desalination cell anode chamber 9 is provided at the other end, a filtering device 18 is provided below the microbial desalination cell anode chamber 9, a lifting pump 8 is provided at the bottom of the vertical shaft 19, one end of the lifting pump 8 is connected to a water reservoir 22 through a pipeline, a recycling pump 23 is provided in the water reservoir 22, the recycling pump 23 is connected to a recycling pipeline 24, and the other end of the recycling pipeline 24 passes through the soil.

[0032] Furthermore, the anode chamber 9 of the microbial desalination cell adopts a "carbon fiber-sawdust" composite mesh material. The carbon fiber has a large specific surface area and can provide a good attachment point for the microorganisms, making it difficult for them to fall off and increasing the reaction time. Sawdust contains rich organic matter, which can provide the carbon source and energy required for degradation and metabolism for microorganisms, and is a renewable raw material.

[0033] Specifically, the anode chamber 9 of the microbial desalination cell selects Shewanella spp. and Halobacterium spp. as anode microorganisms to directly secrete electron carriers and adapt to the high salt content of the wastewater.

[0034] Furthermore, the recycling pump 23 is connected to the second three-way solenoid valve 17 through a pipeline. One end of the second three-way solenoid valve 17 is connected to the recycling pipeline 24, and the other end is connected to the flushing pipeline 7. The flushing pipeline 7 is a polyethylene pipe. Figure 2 As shown, the flushing pipe 7 is connected to one end of a plurality of water suction pipes 5 , and a first solenoid valve 14 is provided at the connection position between the flushing pipe 7 and each water suction pipe 5 .

[0035] Example 3 On the basis of Example 2, the filtering device 18 of the blind pipe drainage recycling system for saline-alkali land improvement of the present invention is mainly equipped with three filter layers, which are a coarse filter layer, a medium filter layer and a fine filter layer from top to bottom. The materials of each filter layer are activated carbon, quartz stone and gravel, and the particle size decreases from top to bottom to filter the drainage; a microbial desalination cell cation exchange membrane 10 is arranged on the surface of the upper coarse filter layer, a microbial desalination cell anion exchange membrane 11 is arranged on the surface of the middle filter material in the middle layer to form a desalination chamber, and a microbial desalination cell cathode chamber 12 is arranged on the surface of the lower fine filter material.

[0036] Furthermore, the cation exchange membrane of the desalination chamber adopts the Shanghai Resin Research Institute (SRI) membrane, and the anion exchange membrane adopts the Aerospace Chemical Membrane Material AEM-300 membrane.

[0037] Furthermore, the cathode chamber 12 of the microbial desalination cell adopts a "carbon paper-molybdenum" composite material to provide a good attachment area and conductivity for the cathode.

[0038] Furthermore, the cathode chamber 12 of the microbial desalination cell can select Paracoccus denitrificans and Candidatus Accumulibacter as cathode microorganisms, which can simultaneously remove nitrogen and phosphorus, reduce the nitrogen and phosphorus concentrations in the wastewater, and reduce the pollution such as eutrophication caused by excessive nitrogen and phosphorus content in the receiving water.

[0039] Furthermore, each cathode is connected to an anode through a wire, which is arranged along the side wall of the shaft, and a waterproof cable is used. A waterproof seal is used at the interface to prevent the wire interface from being directly exposed to the water.

[0040] Furthermore, a water level monitor 20 is provided near the top of the shaft 19 .

[0041] Preferably, the water level monitor 20 is arranged at 50 cm below the wellhead of the vertical shaft 19. When it is detected that the water level in the well is too high, the excess water is promptly discharged through the sewage pipe 21 to prevent the water level from overflowing outside the well.

[0042] Furthermore, a lifting pump 8 is arranged at the bottom of the shaft, and a submersible water pump is selected to lift the drainage water purified by the microbial desalination cell device and the filtering device 18. Example 4 The concealed pipe drainage recycling system for improving saline-alkali land of the present invention comprises four parts: a concealed pipe drainage system, a drainage treatment system, a drainage reuse system and an energy and power system. The concealed pipe drainage system comprises a plurality of water suction pipes 5, which are evenly arranged inside the farmland. One end of the water suction pipes 5 is connected to a water collection pipe 2, and the water collection pipe 2 is connected to each water suction pipe 5 through a tee assembly. One end of the water collection pipe 2 is sealed with a sealing cover, and the other end is connected to a sewage pipe 21.

[0043] The drainage treatment system includes a vertical shaft 19, a water collection pipe 2 and a sewage pipe 21 are connected inside the vertical shaft 19 through a first three-way electromagnetic valve 16, and a filtering device 18 and a microbial desalination battery device are also arranged in the vertical shaft 19. The microbial desalination battery device includes a microbial desalination battery anode chamber 9 arranged at the lower end outlet of the first three-way electromagnetic valve 16, and a microbial desalination battery cation exchange membrane 10, a microbial desalination battery anion exchange membrane 11 and a microbial desalination battery cathode chamber 12 arranged on the filtering device 18. A lifting pump 8 and a water level monitor 20 are also arranged in the vertical shaft 19. The lifting pump 8 is used to transport the water source treated by the filtering device 18 and the microbial desalination battery device to the water reservoir 22. A second electromagnetic valve 15 is arranged on the connecting pipeline between the lifting pump 8 and the water reservoir 22. The water level monitor 20 monitors the water level inside the vertical shaft 19. Once it is detected that the water level inside the vertical shaft 19 exceeds the warning line, the excess water is removed in time to prevent the water level from overflowing outside the well due to excessive water level.

[0044] The drainage reuse system includes a water storage tank 22, a recycling pump 23 is arranged at the bottom of the water storage tank 22, and the recycling pump 23 is connected to the second three-way solenoid valve 17, one end of the second three-way solenoid valve 17 is connected to the recycling pipe 24, and the other end is connected to the flushing pipe 7, and the flushing pipe 7 is connected to one end of a plurality of water suction pipes 5. A first solenoid valve 14 is arranged at the connection between the flushing pipe 7 and each water suction pipe 5.

[0045] When it is necessary to clean the inner wall of the concealed pipe, the opening and closing direction of the second three-way solenoid valve 17 is controlled, and the recycling pump 23 draws out the water in the water reservoir 22 and pressurizes it, and flows it into the flushing pipe 7. At the same time, the first solenoid valve 14 at each connection is opened to introduce water into each water suction pipe 5 to clean the impurities accumulated in the concealed pipe, and use the water pressure to break through the soil particles that may be attached to the water inlet to ensure smooth water inlet.

[0046] The energy power system includes a photovoltaic power generation device 1, which is connected to a lift pump 8, a first solenoid valve 14, a second solenoid valve 15, a first three-way solenoid valve 16, a second three-way solenoid valve 17, a water level monitor 20 and a recycling pump 23 through lines to provide electrical energy for the entire system, which includes photovoltaic panels, inverters, batteries and distribution boxes.

[0047] Example 5 On the basis of Example 4, Figure 3 As shown, the water absorption pipe 5 in the concealed pipe drainage recycling system for improving saline-alkali land of the present invention adopts a polyethylene double-wall corrugated pipe, and water inlet holes 6 are evenly opened on the outer wall of the pipe. A composite filter layer 13 is arranged in the water inlet holes 6. The composite filter layer 13 includes sand and gravel. The sand and gravel are wrapped by geotextile to form the composite filter layer 13 to prevent soil particles from migrating with water and clogging the pipe, thereby improving the water purification effect.

[0048] Specifically, the water inlet holes 6 are arranged in a plum blossom shape, and the outside of the water absorption pipe 5 is wrapped with a permeable membrane 3 and a geotextile 4.

[0049] Preferably, the geotextile type is hot melt spunbond nonwoven geotextile with a mass of 68 g / m 2 , thickness is 0.35mm.

[0050] Preferably, the sand and gravel filter material is 10 cm thick and well graded.

[0051] Furthermore, the corrugated outer wall of the water suction pipe 5 can effectively resist the pressure of soil and groundwater. The corrugated outer wall has a larger contact area with the soil, which increases the friction and prevents the pipe from sliding or shifting during construction or use. Under the condition of water flow scouring, the groove design of the corrugated outer wall can disperse and weaken the impact force of the water flow, extending the service life of the pipe. The inner wall of the water suction pipe 5 is smooth and coated with an anti-sticky coating to reduce the ions or other impurities contained in the soil moisture from adhering to the inner wall of the pipe.

[0052] Example 6 On the basis of Example 4, the water reservoir 22 of the concealed pipe drainage recycling system for saline-alkali land improvement of the present invention is spliced ​​by modular water storage devices. The modular water reservoir is simple to construct, saves materials, is environmentally friendly and has a strong bearing capacity. It is used to collect and store purified water. On the one hand, the water is supplied to the flushing pipe 7 through the reuse pump 23 to remove impurities attached to the inner wall of the pipe. On the other hand, it can be used for agricultural irrigation or hydropower generation, etc., to improve the utilization rate of water resources.

[0053] The working process of the concealed pipe drainage recycling system for improving saline-alkali land of the present invention is as follows: photovoltaic power generation equipment 1 is used to provide electric energy for the whole system, each water absorption pipe 5 collects excess water in farmland soil to the water collection pipe 2, the water outlet at the lower end of the water collection pipe 2 flows into the vertical shaft 19, and the drainage is desalinated and denitrified and dephosphorized by the microbial desalination cell device. At the same time, the filtering device 18 further filters the drainage and flows into the bottom of the vertical shaft 19, and is lifted and pumped into the water reservoir 22 by the lifting pump 8 for storage, and then used in the next step; the water level monitor 20 can also monitor the water level in the vertical shaft, and when the water level is too high, it is discharged in time through the sewage pipe 21.

[0054] Another working process of the concealed pipe drainage recycling system for improving saline-alkali land of the present invention is: when the soil moisture content is low or the water volume in the drainage pipe is small, the dredging work of the water collection pipe 2 and the water suction pipe 5 is started, and the recycling pump 23 starts to work, and opens the first solenoid valve 14, the first three-way solenoid valve 16 and the second three-way solenoid valve 17. The recycling pump 23 extracts the recycled water in the water reservoir 22 and makes it flow into the flushing pipe 7 to clean the water suction pipe 5; the sewage from cleaning the water suction pipe 5 is discharged by merging into the sewage pipe 21.

[0055] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0056] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A concealed pipe drainage recycling system for saline-alkali land improvement, characterized in that: It comprises a water collection pipe (2) buried under the soil and a vertical shaft (19), wherein one end of the water collection pipe (2) is connected to a sealing cover, and the other end extends into the vertical shaft (19) and is connected to a first three-way electromagnetic valve (16), and the water collection pipe (2) located outside the vertical shaft (19) is connected to a plurality of water suction pipes (5), and the plurality of water suction pipes (5) are symmetrically distributed along the axis of the water collection pipe (2); One end of the first three-way solenoid valve (16) is connected to a sewage pipe (21), and the other end is provided with a microbial desalination battery anode chamber (9). The microbial desalination battery anode chamber (9) uses Shewanella and Halophilus as anode microorganisms. A filtering device (18) is provided below the microbial desalination battery anode chamber (9). A lifting pump (8) is provided at the bottom of the vertical shaft (19). One end of the lifting pump (8) is connected to a water reservoir (22) through a pipe. A recycling pump (23) is provided in the water reservoir (22). The recycling pump (23) is connected to a recycling pipe (24). The other end of the recycling pipe (24) passes through the soil.

2. The concealed pipe drainage recycling system for saline-alkali land improvement according to claim 1 is characterized in that: The filtering device (18) comprises, from top to bottom, a coarse filter layer, a medium filter layer and a fine filter layer, wherein the coarse filter layer is activated carbon, the medium filter layer is quartz stone, and the fine filter layer is crushed stone, and the particle sizes of the filter materials in the coarse filter layer, the medium filter layer and the fine filter layer decrease step by step; The surface of the coarse filter layer is provided with a microbial desalination battery cation exchange membrane (10), the surface of the medium filter layer is provided with a microbial desalination battery anion exchange membrane (11), and the surface of the fine filter layer is provided with a microbial desalination battery cathode chamber (12). The microbial desalination battery cathode chamber (12) uses Paracoccus denitrificans and Polyphosphate Bacteria as cathode microorganisms.

3. The concealed pipe drainage recycling system for saline-alkali land improvement according to claim 1 is characterized in that: The recycling pump (23) is connected to a second three-way solenoid valve (17) via a pipeline; one end of the second three-way solenoid valve (17) is connected to the recycling pipeline (24) and the other end is connected to a flushing pipeline (7); the flushing pipeline (7) is connected to one end of a plurality of the water absorption pipelines (5).

4. The concealed pipe drainage recycling system for saline-alkali land improvement according to claim 3 is characterized in that: A first solenoid valve (14) is provided at the connection position between the flushing pipeline (7) and each water absorption pipeline (5).

5. The concealed pipe drainage recycling system for saline-alkali land improvement according to claim 1 is characterized in that: The water absorption pipe (5) is made of polyethylene double-wall corrugated material, the outer wall of the water absorption pipe (5) is corrugated, a plurality of water inlet holes (6) are opened on the water absorption pipe (5), a composite filter layer (13) is arranged in the water inlet holes (6), and the outer wall of the water absorption pipe (5) is wrapped with a permeable membrane (3) and a geotextile (4) in sequence from the inside to the outside.

6. The concealed pipe drainage recycling system for saline-alkali land improvement according to claim 5 is characterized in that: The inner wall of the water suction pipe (5) is coated with an anti-stickiness coating.

7. The concealed pipe drainage recycling system for saline-alkali land improvement according to claim 5 is characterized in that: The composite filter layer (13) comprises sand and gravel, and the sand and gravel are wrapped by geotextile to form the composite filter layer (13).

8. The concealed pipe drainage recycling system for saline-alkali land improvement according to claim 1 is characterized in that: A second solenoid valve (15) is provided on the communication pipeline between the lift pump (8) and the water reservoir (22).

9. The concealed pipe drainage recycling system for saline-alkali land improvement according to claim 1 is characterized in that: A water level monitor (20) is provided near the top of the vertical shaft (19).

10. The concealed pipe drainage recycling system for saline-alkali land improvement according to any one of claims 1 to 9, characterized in that: It also includes a photovoltaic power generation device (1), wherein the photovoltaic power generation device (1) is connected to a lift pump (8), a first solenoid valve (14), a second solenoid valve (15), a first three-way solenoid valve (16), a second three-way solenoid valve (17), a water level monitor (20), and a recycling pump (23) through lines.

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