Underground pipe-recharge well pool salt elimination system for inland saline-alkali soil

Abstract

The invention relates to an inland saline-alkali soil concealed conduit-recharge well pool salt elimination system. The system comprises a monitoring regulation and control system, and a concealed conduit water collection and conveying system, a pretreatment and diversion system and an ecological recharge well pool system which are connected in sequence; the pretreatment and diversion system is used for filtering the saline water conveyed by the concealed pipe water collection and conveying system, reducing the salt content of the saline water and carrying out diversion according to the salt concentration of the pretreated saline water; the ecological recharge well pool system is used for receiving the saline water shunted by the pretreatment and shunting system and carrying out ecological recharge and reutilization; and a sand filter well is arranged in the ecological recharge well pool system, penetrates through the clay layer and is communicated with the underground water layer. The technical problems that in the prior art, a salt discharging system is poor in adaptability to clay areas, low in water discharging efficiency, high in operation and maintenance cost and prone to secondary pollution can be solved.

Description

Technical Field

[0001] This invention relates to the field of saline-alkali land improvement technology, and in particular to a submerged pipe-recharge well pool salt removal system for inland saline-alkali land. Background Technology

[0002] Inland saline-alkali land is one of the major problems of global land degradation. Its formation is mainly due to factors such as arid climate, strong evaporation, high groundwater level, high groundwater mineralization, and salt content in parent material. Moreover, unlike coastal saline-alkali land, inland saline-alkali land is far from the ocean and has relatively scarce water resources. Its drainage channels are not smooth, especially in areas with dense clay layers in the geological structure. The dense clay layer acts as a water-impermeable layer, hindering the natural leaching and discharge of salts, making traditional drainage methods (such as open ditches and underground pipes) ineffective: open ditch drainage takes up a lot of land, is prone to collapse, and is inefficient; the high-salt wastewater discharged by traditional underground pipe drainage cannot infiltrate and tends to accumulate around the pipe, leading to system blockage and failure, and may cause secondary salinization of the surrounding soil.

[0003] While existing technologies have attempted to use structures such as guide pipes to rapidly direct water to aquifers to improve precipitation or drainage efficiency, they still have significant limitations. For example, current technologies generally employ only a "fixed filter media + guide pipe" drainage structure, which has poor adaptability and struggles to cope with complex conditions in inland clay areas, such as high soil compaction, deep groundwater levels, and significant water resistance variations. This makes them prone to clogging, efficiency degradation, and low salt removal efficiency. Furthermore, existing salt removal systems often have a limited function, focusing solely on the large-scale discharge of high-salinity wastewater. Excessive discharge of high-salinity wastewater not only leads to secondary pollution problems such as groundwater salinity accumulation but also causes soil salinization. Moreover, existing salt removal systems typically only discharge water without addressing the underlying causes, lacking synergy with soil improvement and ecological restoration, often necessitating the construction of separate ecological restoration systems. In addition, the working environment of salt drainage systems is often harsh, and problems such as salt crystallization place high demands on the reliability of the salt drainage system. In order to ensure good salt drainage / water discharge effect, existing technologies often set up a variety of complex / expensive mechanical equipment in the salt drainage system, such as negative pressure pumps or multi-stage pumping stations in the drainage pipes. This leads to a decrease in the reliability of the salt drainage system, and the pressure of construction, operation and maintenance of the salt drainage system is greater, making the already limited budget for saline-alkali land management even more strained.

[0004] Therefore, there is an urgent need in this field for a desalination system that can overcome the limitations of clay layers and achieve efficient desalination, resource recovery, and ecological restoration. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides an inland saline-alkali land underground pipe-recharge well pool salt drainage system, which solves the technical problems of poor adaptability of the existing salt drainage system to clay areas, low drainage efficiency, high operation and maintenance costs, and easy generation of secondary pollution.

[0007] (II) Technical Solution

[0008] This invention provides a subsurface pipe-recharge well system for desalination in inland saline-alkali land, comprising: a monitoring and control system and a subsurface pipe water collection and transportation system, a pretreatment and diversion system, and an ecological recharge well system connected in sequence; the monitoring and control system is used to detect and regulate the operation of other systems; the subsurface pipe water collection and transportation system is used to collect saline water from the soil and transport it to the pretreatment and diversion system; the pretreatment and diversion system is used to desalinate the saline water transported from the subsurface pipe water collection and transportation system, reducing its salt content and diverting it according to the salt concentration of the pretreated saline water; the ecological recharge well system is used to receive the saline water produced by the pretreatment and diversion system and perform ecological recharge and / or reuse;

[0009] The ecological recharge well system includes an ecological recharge well that receives saline with a salt concentration below a predetermined threshold and a high-salt recovery well that receives saline with a salt concentration above a predetermined threshold. The ecological recharge well is equipped with a sand filter well, which is connected to the groundwater layer.

[0010] Optionally, the concealed pipe water collection and transportation system includes several pipe network subsystems; each pipe network subsystem includes several water collection concealed pipes, multiple primary water transmission concealed pipes, and secondary water transmission concealed pipes; several seepage outlets are provided on the pipe walls of the water collection concealed pipes; the water collection concealed pipes, primary water transmission concealed pipes, and secondary water transmission concealed pipes are all inclined, with a slope of 0.2%-0.6%; several water collection concealed pipes are connected to one primary water transmission concealed pipe; multiple primary water transmission concealed pipes are connected to secondary water transmission concealed pipes;

[0011] The secondary water supply pipe is also equipped with a low-pressure node cavity to enhance the low-pressure environment in the primary water supply pipe; along the direction of brine flow in the secondary water supply pipe, the low-pressure node cavity includes a constriction cone, a throttling tube, and a diffusion cone; the primary water supply pipe is connected to the side wall of the throttling tube in the low-pressure node cavity.

[0012] Optionally, the two ends of the water collection pipe are a venting end and a water outlet end, respectively; the water outlet end is connected to the primary delivery pipe; the venting end is connected to a vent pipe, the outlet of which is higher than the ground surface and connected to the outside; the diameter of the vent pipe outlet does not exceed 20% of the diameter of the water collection pipe.

[0013] A flow meter is installed at the outlet of the primary water transmission pipe to monitor the flow rate of the brine output from the primary water transmission pipe; a flow regulating valve is installed at the outlet of the secondary water transmission pipe; both the flow meter and the flow regulating valve are connected to the monitoring and control system; the outlet of the secondary water transmission pipe is connected to the pretreatment and diversion system.

[0014] Optionally, the underground water collection and delivery system also includes a flushing subsystem; the flushing subsystem is connected to the relatively high end of the secondary water delivery underground pipe and is used to inject clean water into the secondary water delivery underground pipe.

[0015] Optionally, the pretreatment and diversion system includes a pretreatment chamber and a diversion module; the inlet of the pretreatment chamber is connected to a submerged water collection and delivery system; inside the pretreatment chamber, a coarse filter screen, a zeolite adsorption layer, and a water quality monitoring unit are sequentially arranged along the brine flow direction; the water quality monitoring unit is used to monitor the salt concentration of the brine after passing through the zeolite adsorption layer; the outlet of the pretreatment chamber is connected to the diversion module; the diversion module diverts the brine according to the monitoring results of the water quality monitoring unit; both the water quality monitoring unit and the diversion module are communicatively connected to the monitoring and control system.

[0016] Optionally, the mesh size of the grid filter is 3-8mm; the grid filter is inclined toward the inlet direction away from the pretreatment chamber, so that the angle between it and the horizontal plane is 45-75 degrees; the zeolite in the zeolite filter layer is modified activated zeolite; the diversion module includes a multi-way valve.

[0017] Optionally, the ecological recharge well pool includes a pool body; the pool body is a semi-underground structure with a top cover; and a sand filter well is located at the bottom of the pool body.

[0018] Optionally, the sand filter well includes a well casing and a fine sand filter layer, a bacteria-carrying ceramic particle filter layer, a coarse sand filter layer, and a gravel filter layer sequentially covering the outer circumference of the well casing wall. The thickness of each filter layer is 150-300 mm. The well casing includes a filtration section and a conveying section. The filtration section is located in the pool body, and the conveying section passes through the bottom of the pool body and is connected to the groundwater layer. The filtration section of the well casing is provided with filter holes for collecting water filtered by the fine sand filter layer, the bacteria-carrying ceramic particle filter layer, the coarse sand filter layer, and the gravel filter layer. The porosity of the filter holes on the filtration section is 15-20%. The pore size of the filter holes is smaller than the minimum particle size of the fine sand in the fine sand filter layer.

[0019] The particle size of the bacterial-loaded ceramic granule layer is 5-10 mm, and the porosity is not less than 30%. The bacterial-loaded ceramic granule layer is loaded with salt-tolerant bacteria for removing organic pollutants from brine.

[0020] Optionally, the top cover is provided with several planting holes, in which deep-rooted salt-tolerant plants are planted, including at least one of the following: Suaeda salsa, Artemisia argyi, Reed, Salicornia glutinosa, Deer antler velvet, Tamarix chinensis and Elaeagnus angustifolia. The roots of the deep-rooted salt-tolerant plants are located in the fine sand filter layer (16), the bacteria-laden ceramic granule filter layer (17), the coarse sand filter layer (18) and the gravel filter layer (19). The bottom of the top cover is also connected to a hanging cage, which is filled with soil conditioner. The soil conditioner includes at least one of the following: crushed brick, fly ash, desulfurized gypsum, phosphogypsum and lime.

[0021] Optionally, the high-salt recovery well pool includes a buffer pool for temporarily storing brine with a salt concentration higher than a predetermined threshold and an evaporation crystallization pool connected in sequence; the top of the evaporation crystallization pool is covered with an insulating membrane for increasing the temperature inside the evaporation crystallization pool; the insulating membrane is inclined.

[0022] (III) Beneficial Effects

[0023] The inland saline-alkali land underground pipe-recharge well pool desalination system (hereinafter referred to as the desalination system) of the present invention, through the cooperation of an underground pipe water collection and transportation system, a pretreatment and diversion system, and an ecological recharge well pool system, achieves different treatment paths for the collected saline water (hereinafter referred to as desalinated water) based on the different salt concentrations of the pretreatment and diversion system and the ecological recharge well pool system compared to the prior art. This allows for the safe recharge of qualified desalinated water, avoiding the discharge of large amounts of high-concentration desalinated water into the ground, thus preventing secondary pollution and salt return. It also enables the resource recovery of high-concentration desalinated water, reducing environmental pressure. The recovered salt crystals can be used as snow melting agents or industrial raw materials, recovering some funds and reducing the budget pressure of the desalination system during operation and maintenance. Furthermore, because the ecological recharge well pool of the present invention is equipped with a sand filter well that directly reaches the groundwater layer, it can directly guide the desalinated water flowing into the ecological recharge well pool into the groundwater layer, giving the desalination system a faster drainage speed and effectively avoiding the problem of precipitation difficulties caused by clay layers. After passing through sand filters, the salinity of the brine in the ecological recharge well pool is further reduced, which can further reduce potential secondary pollution and other problems. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the architecture of the inland saline-alkali land underground pipe-recharge well salt drainage system of the present invention;

[0025] Figure 2 This is a schematic diagram of the low-pressure node cavity in the secondary water conveyance underground pipe of the salt discharge system of the inland saline-alkali land underground pipe-recharge well pool of the present invention.

[0026] Figure 3 This is a schematic diagram of the pretreatment chamber of the inland saline-alkali land underground pipe-reinjection well salt drainage system of the present invention.

[0027] Figure 4 This is a schematic diagram of the structure of the ecological recovery well pool of the inland saline-alkali land underground pipe-recharge well pool salt drainage system of the present invention.

[0028] Figure 5 This is a schematic diagram of the high-salt recovery well pool of the inland saline-alkali land underground pipe-reinjection well pool salt discharge system of the present invention;

[0029] Figure 6 This is a schematic diagram of the ventilation pipe and water collection pipe of Embodiment 1 of the salt drainage system for inland saline-alkali land underground pipe-recharge well pool of the present invention.

[0030] Figure 7 This is a schematic diagram of the flushing subsystem of Embodiment 1 of the salt drainage system for inland saline-alkali land underground pipe-reinjection well pool of the present invention.

[0031] [Attached image captions]

[0032] 1: Sand filter well; 2: Groundwater layer; 3: Primary water conveyance pipe; 4: Secondary water conveyance pipe; 5: Contraction cone pipe; 6: Throttling pipe; 7: Diffusion cone pipe; 8: Siphon reinforcement pipe; 9: Pretreatment chamber; 10: Coarse filter screen; 11: Zeolite adsorption layer; 12: Water quality monitoring unit; 13: Diversion module; 14: Pool body; 15: Well pipe; 16: Fine sand filter layer; 17: Bacterial-loaded ceramic granule filter layer; 18: Coarse sand filter layer; 19: Gravel filter layer; 20: Top cover; 21: Planting hole; 22: Hanging cage; 23: Soil conditioner; 24: Evaporation crystallization pool; 25: Insulation membrane; 26: Water collection trough; 27: Water collection pipe; 28: Ventilation pipe; 29: Clear water tank; 30: Booster pump. Detailed Implementation

[0033] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] like Figure 1 As shown, this invention provides a subsurface pipe-recharge well system for desalination in inland saline-alkali land, comprising: a monitoring and control system, and a subsurface pipe water collection and transportation system, a pretreatment and diversion system, and an ecological recharge well system connected in sequence. The monitoring and control system is used to detect and regulate the operation of other systems. The subsurface pipe water collection and transportation system collects saline water from the soil and transports it to the pretreatment and diversion system. The pretreatment and diversion system desalinates the saline water transported by the subsurface pipe water collection and transportation system, reducing its salt content and diverting it according to the salt concentration of the pretreated saline water. The ecological recharge well system receives the saline water produced by the pretreatment and diversion system and performs ecological recharge and / or reuse.

[0035] The ecological recharge well system includes ecological recharge wells that receive saline solution with a salt concentration below a predetermined threshold and high-salt recovery wells that receive saline solution with a salt concentration above a predetermined threshold. For example... Figure 3 As shown, the ecological recharge well pool is equipped with a sand filter well 1, which penetrates the clay layer and is connected to the groundwater layer 2.

[0036] like Figure 1 As shown, the inland saline-alkali land underground pipe-recharge well pool desalination system (hereinafter referred to as the desalination system) of the present invention, through the cooperation of an underground pipe water collection and transportation system, a pretreatment and diversion system, and an ecological recharge well pool system, addresses the issue of salt concentration in the collected saline water (hereinafter referred to as desalinated water) by using different treatment paths in conjunction with the pretreatment and diversion system and the ecological recharge well pool system. This allows for the safe recharge of qualified desalinated water, avoiding the discharge of large amounts of high-concentration desalinated water into the ground and preventing secondary pollution and salt return. Furthermore, it enables the resource recovery of high-concentration desalinated water, reducing environmental pressure. The recovered salt crystals can also be used as de-icing agents or industrial raw materials, recovering some funds and reducing the budget pressure of the desalination system during operation and maintenance. Simultaneously, the ecological recharge well pool of the present invention also includes a sand filter well 1 that directly reaches the groundwater layer 2, which can directly guide the desalinated water flowing into the ecological recharge well pool into the groundwater layer 2. This gives the desalination system a faster drainage speed, effectively avoiding the problem of precipitation difficulties caused by clay layers. After passing through sand filter well 1, the salinity of the brine in the ecological recharge well pool will be further reduced, which can further reduce potential secondary pollution and other problems.

[0037] The combination of the underground pipe water collection and transportation system, the pretreatment and diversion system, and the ecological recharge well pool system of this invention forms a system engineering that integrates salt collection, transportation, purification, differentiated treatment, and ecological synergy. It can achieve high drainage efficiency and salt removal effect while ensuring that the operating cost of the entire salt removal system is low and relatively environmentally friendly. Its drainage efficiency is also less affected by soil quality and is not prone to secondary pollution.

[0038] When constructing the salt drainage system of this invention, site survey and design should be carried out first: conduct geological surveys of the target inland saline-alkali area to determine the distribution and thickness of the clay layer with water-resistant properties (i.e., the clay layer that is not easily permeable by water), as well as the groundwater depth in the area; based on the survey results, plan the laying route of the underground pipes for collecting water in the transportation system, the location and number of ecological recharge wells, etc. (preliminary planning should be adapted to local conditions and will not be elaborated here), and ensure that the sand filter well 1 of the ecological recharge well can penetrate the clay layer and extend to the groundwater layer 2 below the clay layer.

[0039] like Figure 1 and Figure 2As shown, preferably, the underground water collection and transportation system includes several pipe network subsystems. Each pipe network subsystem includes several underground water collection pipes 27, multiple primary underground water transmission pipes 3, and secondary underground water transmission pipes 4. Several underground water collection pipes 27 are connected to one primary underground water transmission pipe 3, and multiple primary underground water transmission pipes 3 are connected to the secondary underground water transmission pipes 4, forming an underground water collection and transportation network. The overall shape of this network can be a conventional herringbone structure or a tree structure; of course, other shapes are also possible, selected according to actual conditions, as long as it can effectively collect and transport water. The underground pipes are laid along the planned laying route, below the soil surface layer (cultivated layer) and above the clay layer.

[0040] The wall of the water collection pipe 27 is equipped with several seepage ports. The saline water in the soil (formed by the dissolution of salt in the soil by water from artificial irrigation or natural rainfall) can seep into the water collection pipe 27 through the seepage ports, and then be transported to the primary water supply pipe 3 through the water collection pipe 27, and then to the secondary water supply pipe 4.

[0041] Both the primary water transmission underground pipe 3 and the secondary water transmission underground pipe 4 are seamless pipes with one end closed, and are all laid underground to ensure the full-process sealing of the desalination water during transportation, prevent desalination water leakage, and ensure the operation of the subsequent flushing subsystem and other related structures, such as preventing salt backflow in the pipes during the operation of the flushing subsystem.

[0042] The underground water collection pipe 27, the primary underground water transmission pipe 3, and the secondary underground water transmission pipe 4 are all installed at an incline, with their burial depths increasing sequentially. This allows the underground water collection and transmission system to transport desalinated water by gravity, avoiding the use of mechanical structures such as negative pressure pumps and ensuring the reliability of the underground water collection and transmission system during long-term use. The slope of the underground water collection pipe 27, the primary underground water transmission pipe 3, and the secondary underground water transmission pipe 4 is 0.2%-0.6%, preferably 0.4%-0.6%, ensuring that the desalinated water flows entirely by gravity. Furthermore, it should be noted that this slope is the optimal slope under normal conditions, considering drainage effect and construction cost. In cases with special environmental / soil conditions, such as saline-alkali land (e.g., with a frozen soil layer), the slope can be appropriately increased to increase the drop and improve drainage effect.

[0043] like Figure 2 As shown, the secondary water conveyance pipe 4 is also equipped with several low-pressure node cavities to enhance the low-pressure environment within the primary water conveyance pipe 3. Along the brine flow direction in the secondary water conveyance pipe 4, the low-pressure node cavities include a constricting cone pipe 5 (gradually narrowing structure), a throttling pipe 6, and a diffusing cone pipe 7 (gradually expanding structure) connected in sequence. The constricting cone pipe 5 is a gradually narrowing structure, with its diameter gradually decreasing along the brine flow direction until it connects with the throttling pipe 6. The diffusing cone pipe 7 is a gradually expanding structure, with its initial diameter being the same as the throttling pipe 6, and then its diameter gradually increasing along the brine flow direction until it is the same as that of the secondary water conveyance pipe 4.

[0044] The low-pressure node cavity utilizes the tapered structure of the contraction cone 5, the throttling tube 6, and the expanding structure of the diffusion cone 7 to form a Venturi-like structure. The flow velocity of the desalinated water increases as it passes through the contraction cone 5, reaching its maximum in the throttling tube 6. A low-pressure zone is formed within the low-pressure node cavity, drawing water (and air) from the primary water conveyance pipe 3 into this low-pressure zone (pressure difference-driven suction). This water mixes with the high-speed water flow in the secondary water conveyance pipe 4 before flowing away. Simultaneously, because the primary conveying pipe is seamless, the desalinated water and air inside are also drawn away, creating a low-pressure environment. This further draws into the collection pipe 27, creating a low-pressure environment within it as well. This allows the collection pipe 27 to actively draw desalinated water from the soil, accelerating its accumulation, increasing its collection speed and efficiency, and expanding its collection range. This allows it to collect desalinated water over a larger area, further improving the desalination efficiency of the system and preventing the infiltration and residue of desalinated water. The primary water supply pipe 3 connects to the side wall of the secondary water supply pipe 4 at the throttling pipe 6, ensuring the formation of a low-pressure environment in the primary water supply pipe 3. The connection between the primary water supply pipe 3 and the throttling pipe 6 uses a rounded transition to ensure that the desalinated water in the primary water supply pipe 3 flows smoothly into the main flow in the secondary water supply pipe 4, avoiding excessive turbulence that could interfere with the operation of the low-pressure node cavity and reduce energy loss. Alternatively, the primary water supply pipe 3 can be connected to the contraction cone pipe 5 or 0-2m upstream of the low-pressure node cavity, but the effect may be less satisfactory.

[0045] Preferably, the length of the contraction cone 5 is 1-1.5 times the diameter of the secondary water conveyance pipe 4, and the length of the throttling pipe 6 is 0.5-1 times the diameter of the secondary water conveyance pipe 4, and its diameter is 0.35-0.5 times the diameter of the secondary water conveyance pipe 4. This ensures the stability of the flow velocity and pressure of the desalinated water within the throttling pipe 6 and avoids problems such as blockage of the throttling pipe 6, thus ensuring the reliability of the desalination system of this invention. The length of the expansion cone is 3-5 times the diameter of the secondary water conveyance pipe 4 to prevent the desalinated water from separating from the pipe wall and generating eddies, ensuring smooth water flow, avoiding excessive loss of kinetic energy of the desalinated water, and preventing a decrease in drainage efficiency.

[0046] The materials for the water collection pipe 27, the primary water supply pipe 3, and the secondary water supply pipe 4 should be high-strength materials, such as high-strength PVC + carbon fiber composite pipes, to ensure that they will not deform and can maintain their strength for a long time under conditions of relatively high soil density and high soil pressure in clay areas.

[0047] The outer side of the water collection pipe 27 is covered with a water collection filter layer, which is made of quartz sand with a particle size of 2-5mm and a thickness of 100-150mm to prevent excessive impurities from entering the water collection pipe 27. The seepage outlet is equipped with a structure that allows water to seep in quickly and prevents mud and sand, such as a non-woven fabric seal, to further prevent clogging.

[0048] The water collection pipe 27 has an air outlet and a water outlet at its two ends. The water outlet is connected to the primary water delivery pipe. The air outlet is equipped with an air vent pipe 28, the outlet of which is higher than the ground surface and connected to the outside. The air vent pipe 28 balances the internal air pressure of the water collection pipe 27, the primary water delivery pipe 3, and the secondary water delivery pipe 4 during drainage, reducing air resistance and improving initial water collection efficiency. This allows the salt water in the soil to flow smoothly into the water collection pipe 27 and into the primary water delivery pipe 3 under gravity at the beginning of artificial irrigation or natural rainfall, before the salt drainage system of this invention is fully operational. This ensures that the salt drainage system of this invention can effectively collect salt water even in clay areas where the soil is relatively dense and water resistance is high.

[0049] Preferably, the diameter of the outlet of the vent pipe 28 does not exceed 20% of the diameter of the water collection pipe 27, and more preferably does not exceed 10%. The smaller diameter of the vent pipe 28 effectively prevents foreign objects from entering. Furthermore, it is important that due to the small orifice of the vent pipe 28, its ventilation capacity is limited. This effectively maintains the stability of the low-pressure environment within the water collection pipe 27 and the primary water supply pipe 3. Its lower ventilation capacity ensures a high suction force within the water collection pipe 27 and the primary water supply pipe 3 during the operation of the salt drainage system of this invention, further improving the water collection effect of the salt drainage system. Simultaneously, it allows a certain amount of air to be drawn in during the operation of the salt drainage system, preventing excessive suction force within the pipes (excessive pressure difference between the inside and outside of the pipe), which could damage the pipes or surrounding soil, and avoiding backflow problems after the salt drainage system stops.

[0050] Preferably, the outlet of the vent pipe 28 is also equipped with a dust cover.

[0051] Along the direction from the vent end to the water outlet end, the density of seepage holes on the pipe wall of the water collection pipe 27 gradually increases. Since the water collection pipe 27 is installed at an angle underground, in clay areas, the deeper it is, the greater the water resistance generally is. By gradually increasing the density of seepage holes, the water collection capacity of the water collection pipe 27 is ensured. The arrangement of the seepage holes can be selected according to the actual situation, such as uniform distribution, spiral distribution, or other distribution methods, as long as the water permeability is ensured.

[0052] like Figure 2As shown, preferably, the secondary water conveyance pipe 4 also includes a siphon reinforcement pipe 8, which is located at the connection between the secondary water conveyance pipe 4 and the pretreatment and diversion system. The height difference between the two ends of the siphon reinforcement pipe 8 is not less than 0.5m. The siphon reinforcement pipe 8 creates a significant height difference within the secondary water conveyance pipe 4, thereby generating negative pressure at the siphon reinforcement pipe 8. This siphon draws water from the secondary water conveyance pipe 4, ensuring a high flow velocity even at a relatively low overall slope. This improves the effect of the low-pressure node cavity and collectively enhances the water conveyance efficiency of the pipe network subsystem, thereby improving the drainage and desalination efficiency of the desalination system of this invention. Simultaneously, the higher flow velocity further prevents the deposition of impurities in the secondary water conveyance pipe 4, avoiding blockages and improving the reliability of the desalination system of this invention.

[0053] Preferably, the slope of the siphon reinforcement pipe 8 is not less than 1%, and more preferably 1%-5%. This further ensures the water flow rate.

[0054] In addition, the diameter and length of the water collection pipe 27, the primary water supply pipe 3, and the secondary water supply pipe 4, as well as the aperture parameters of the seepage outlet on the water collection pipe 27, can also be designed and selected according to the actual saline-alkali land conditions, rainfall intensity, artificial irrigation amount, and other actual conditions, using conventional methods. This invention will not elaborate on these details.

[0055] The concealed pipe water collection and transportation system of the present invention relies entirely on gravity for water flow transportation. Through the coordinated operation of the vent, low-pressure node cavity and siphon reinforcement pipe 8, the present invention can achieve high water collection, salt removal and drainage effects without the need for an external pump. Its pipeline is also less prone to blockage, which not only has high reliability, but also low construction cost and low investment in operation and maintenance.

[0056] Preferably, a flow meter is installed at the outlet of the primary water transmission pipe 3 to monitor the flow rate of the desalinated water output from the primary water transmission pipe 3. A flow regulating valve is installed at the outlet of the secondary water transmission pipe 4 (or the outlet of the siphon reinforcement pipe 8) to control the maximum allowable flow rate of desalinated water within the secondary water transmission pipe 4. Both the flow meter and the flow regulating valve are communicatively connected to the monitoring and control system.

[0057] The flow regulating valve controls the maximum flow rate of water allowed through the secondary water transmission pipe 4 based on the flow rate of the desalinated water in all the primary water transmission pipes 3 monitored by the flow meter. This keeps the desalinated water in the secondary water transmission pipe 4 in a full-pipe state, ensuring the water flow velocity and the stability of the low-pressure environment formed at the low-pressure node cavity.

[0058] Preferred, such as Figure 1As shown, the underground water collection and transportation system also includes a flushing subsystem. The flushing subsystem is connected to the relatively high end of the secondary water supply underground pipe 4 and is used to inject clean water into the secondary water supply underground pipe 4 when salt discharge stops. Specifically, in the salt discharge system of this invention, when the flow meter detects that the water flow rate in the primary water supply underground pipe 3 is lower than or equal to a predetermined value for a certain period of time (generally, the water flow rate in the primary water supply underground pipe 3 is 0, and the duration exceeds 30 minutes), salt discharge is considered to have stopped, the flow regulating valve is fully opened (the flow regulating valve switches to the fully open state), and the flushing subsystem starts operating, injecting clean water (the clean water source can be groundwater, surface water, high-salt recovery well water, etc.) into the secondary water supply underground pipe 4. Then, the residual desalinated water in the pipe is flushed away and replaced with clean water, effectively avoiding the salt crystallization and blockage problem caused by the long-term stagnation and evaporation of desalinated water in the pipe. This achieves preventative and automated pipe maintenance, effectively improving the reliability of the salt discharge system of this invention, enabling it to maintain long-term stable operation for several years, and significantly reducing its maintenance costs. At the same time, the injected clean water can also clean the subsequent pretreatment and diversion systems and ecological reinjection well pool systems, removing excess salt residue (such as salt in the zeolite filter layer) from their structures, further improving the reliability of these systems and reducing their maintenance intervals.

[0059] After cleaning is completed, the flow regulating valve is completely closed, and the flushing subsystem continues to inject water until the secondary water supply pipe 4 is completely filled, maintaining positive pressure in the pipe and forming a clean water filling section (water seal), avoiding the crystallization and corrosion of residual salt on the inner wall of the pipe, further reducing the corrosion rate of the pipe and valve, extending the service life of the equipment, and enabling the salt discharge system of the present invention to quickly form a full pipe flow when it is started next time.

[0060] When the salt is discharged next time, the newly generated brine will flow into the cleaning water seal. The flow meter detects the continuous water flow, the flow regulating valve opens, and the salt discharge system of the present invention starts to operate. Under the action of the cleaning water seal in the secondary water supply pipe 4, the secondary water supply pipe 4 can immediately form a full pipe flow, quickly start up and generate a low-pressure environment, and quickly drain and discharge salt. It is not only highly reliable, but also has a fast response speed.

[0061] The structure of the flushing subsystem is set according to specific circumstances. It can be directly connected to the water source for irrigation, and can be used as needed; or a water tank can be set up to store relatively clean water such as rainwater and water recovered from high-salt recovery wells in advance, and then transported to the secondary transport underground pipe 4 by gravity or a corresponding pump.

[0062] The monitoring and control system monitors the operation of the salt discharge system through a communication connection and adjusts the operation of the entire salt discharge system according to the actual situation to ensure the efficient operation of the entire salt discharge system.

[0063] Preferred, such as Figure 3As shown, the pretreatment and diversion system includes a pretreatment chamber 9 and a diversion module 13 connected in sequence. The inlet of the pretreatment chamber 9 is connected to a submerged water collection and delivery system. Inside the pretreatment chamber 9, a coarse filter screen 10, a zeolite adsorption layer 11, and a water quality monitoring unit 12 are sequentially arranged along the flow direction of the desalinated water. One pretreatment chamber 9 can be connected to one or more pipe network subsystems, depending on the size of the pretreatment and diversion system being constructed. Preferably, the pretreatment chamber 9 corresponds one-to-one with the pipe network subsystem, and the diversion module 13 corresponds one-to-one with the pretreatment chamber 9, ensuring the purification effect of the pretreatment chamber 9 and the diversion effect of the diversion module 13.

[0064] Preferably, the mesh size of the grid filter is 3-8mm. The grid filter is inclined towards the direction away from the inlet of the pretreatment chamber 9, with an angle of 45-75 degrees between it and the horizontal plane. The grid filter filters impurities while simultaneously using gravity to cause them to slide down and collect, facilitating cleaning. The grid filter can be a pull-out type, allowing for easy removal and cleaning of the slid-down impurities.

[0065] The zeolite in the zeolite filter layer is modified and activated zeolite. The distance traveled by the brine through the zeolite filter layer is no less than 1.5m, ensuring the contact area and reaction time between the brine and the modified zeolite. This ensures the efficient and stable adsorption and removal of cations such as sodium ions in the brine by the zeolite filter layer, reducing the sodium adsorption ratio of the brine after passing through the zeolite filter layer and reducing its environmental pollution.

[0066] Preferably, the zeolite filter layer is S-shaped, and the pretreatment chamber 9 is provided with an S-shaped flow channel, in which the zeolite filter layer is disposed. The cross-sectional area of ​​the flow channel is determined based on the expected amount of desalinated water to be treated, and is preferably not less than 100 cm². 2 By designing an S-shaped flow channel, the overall length of the pretreatment chamber 9 is shortened.

[0067] The water quality monitoring unit 12 is used to monitor the salt concentration of the desalinated water after passing through the zeolite adsorption layer 11. The outlet of the pretreatment chamber 9 is connected to the diversion module 13, which diverts the desalinated water according to the monitoring data from the water quality monitoring module. Both the water quality monitoring unit 12 and the diversion module 13 are communicatively connected to the monitoring and control system.

[0068] Preferably, the water quality monitoring unit 12 is a conductivity sensor, and the diversion module 13 is a multi-way valve (electric multi-way valve).

[0069] Preferably, when the water quality monitoring unit 12 detects that the conductivity of the desalinated water is greater than 5 mS / cm, it determines that the desalinated water has a high salt content and transports it to a high-salt recovery well pond through the diversion module 13. When the water quality monitoring unit 12 detects that the conductivity of the desalinated water is less than or equal to 5 mS / cm, it transports the desalinated water to an ecological recharge well pond through the diversion module 13. When the diversion module 13 responds to the monitoring results of the water quality monitoring unit 12, it can set an appropriate delay time based on the distance between the desalinated water and the diversion module 13 to ensure accurate delivery of the desalinated water.

[0070] The pretreatment chamber 9 can be set at an angle or horizontally. The desalination water inside it will move towards the diversion module 13 under the push of the desalination water in the secondary water conveyance pipe 4.

[0071] The desalinated water from the diversion module 13 can flow into the ecological recharge well or high-salinity recovery well via a pump or under gravity. However, considering reliability and service life, it is preferable to allow the water to flow into the ecological recharge well or high-salinity recovery well under gravity. In this case, the ecological recharge well or high-salinity recovery well should be relatively deep to ensure natural water flow. Of course, if it is inconvenient to construct a deep ecological recharge well or high-salinity recovery well, a pump can be used for diversion. A small number of pumps will not significantly increase maintenance costs and can reduce construction requirements to some extent.

[0072] Preferred, such as Figure 4 As shown, the ecological recharge well pool includes a pool body 14 and a sand filter well 1. The pool body 14 is a semi-underground structure (i.e., part of the structure is built below the ground surface, and part of the structure is exposed on the ground surface), and a top cover 20 is provided on its top. The sand filter well 1 is located at the bottom of the pool body 14, preferably at the center of the bottom.

[0073] Preferred, such as Figure 4 As shown, the sand filter well 1 includes a well pipe 15, which comprises a filtration section and a conveying section. The filtration section is located within the pool body 14, and its outer periphery is sequentially covered with a fine sand filter layer 16, a bacterial-carrying ceramic particle filter layer 17, a coarse sand filter layer 18, and a gravel filter layer 19, in a direction away from its outer periphery. The thickness of each filter layer is 150-300 mm. The filtration section of the well pipe 15 is provided with filter holes, with an opening rate of 15-20%.

[0074] like Figure 4 As shown, the conveying section passes through the bottom of the pool 14 and connects with the groundwater layer 2. After the desalinated water enters the ecological recharge well pool, it needs to pass through the gravel filter layer 19, the coarse sand filter layer 18, the bacteria-laden ceramic particle filter layer 17, and the fine sand filter layer 16 in sequence. Then, it enters the filter section of the well pipe 15 through the filter holes, flows into the conveying section, and then flows directly into the groundwater to complete the recharge.

[0075] Among them, fine sand, ceramsite, coarse sand and gravel form a physical filtration barrier to filter impurities and reduce the salinity of the desalinated water entering the groundwater layer 2.

[0076] Preferably, the particle size of the bacterial-loaded ceramsite layer is 5-10 mm, and the porosity is not less than 30%. The bacterial-loaded ceramsite layer is loaded with salt-tolerant bacteria (such as Pseudomonas, Bacillus subtilis, and Bacillus licheniformis) for removing organic pollutants from the desalinated water. The salt-tolerant bacteria loaded on the bacterial-loaded ceramsite can be a single bacterial group or a complex bacterial group composed of multiple bacteria to ensure the synergistic degradation of multiple organic pollutants.

[0077] The bacterial-loaded ceramic particles have a porous structure with a porosity of no less than 30%, ensuring effective bacterial loading. During loading, a biofilm loading method is used. Selected salt-tolerant bacteria, culture medium, and bacterial-loaded ceramic particles are mixed and cultured for a certain period. Loading is complete once the salt-tolerant bacteria have multiplied extensively within the ceramic particles and produced a stable biofilm. The salt-tolerant bacteria, in conjunction with their secreted biofilm, effectively degrade dissolved organic matter in the brine, significantly reducing the chemical oxygen demand (COD) and biological oxygen demand (BOD) of the desalinated water, achieving deep purification of the reinjected desalinated water. Simultaneously, the activity of the microorganisms also produces organic acids and other substances, effectively preventing the gravel filter layer 19, coarse sand filter layer 18, bacterial-loaded ceramic particle filter layer 17, and fine sand filter layer 16 from caking due to prolonged exposure to a saline-alkali environment. This prevents them from losing their filtration effect or experiencing reduced permeability, leading to desalinated water accumulation. This further improves the reliability of the desalination system of this invention, ensuring its long-term maintenance-free operation.

[0078] More preferably, the fine sand filter layer 16 has a particle size of 0.5-1 mm and a thickness of 100-150 mm; the coarse sand filter layer 18 has a particle size of 2-5 mm and a thickness of 200-300 mm; and the gravel filter layer 19 has a particle size of 10-20 mm and a thickness of 150-200 mm. All the fine sand, coarse sand, and gravel have been washed and screened, and the mud content does not exceed 3 wt%. Different filter layers can be separated and fixed using perforated plates. Alternatively, a longer flow channel structure can be configured and the filter layers filled sequentially, such as a "U"-shaped flow channel structure, but this may affect the drainage efficiency.

[0079] The filter holes on the well casing 15 should have a diameter smaller than that of fine sand particles, allowing water to pass through while preventing filter media loss. Additionally, the well casing 15 should be made of high-strength tubing capable of withstanding geological pressure (such as stainless steel tubing, high-strength PVC + carbon fiber tubing, etc.), and an internal support frame can be further installed to prevent deformation of the tubing.

[0080] Preferably, the pool body 14 is lined with an aging-resistant geomembrane (such as a high-density polyethylene geomembrane), and the geomembranes are connected by hot-melt welding. The welding strength is not less than 80% of the strength of the geomembrane parent material to ensure the seepage prevention effect.

[0081] Preferably, the ecological recharge well pool is equipped with at least one sand filter well 1 and is connected to at least one pretreatment chamber 9 (via the diversion module 13). More preferably, in the ecological recharge well pool, the pool body 14 is formed by concrete casting, the concrete thickness of the side walls and bottom of the pool body 14 is not less than 200mm, preferably 200-300mm, the length of the pool body 14 is 3-5m, the width is 2-4m, and the depth is 2-3m, the diameter of the well pipe 15 is 200-300mm, and the pool body 14 is equipped with one sand filter well 1 and is connected to 1-3 pretreatment chambers 9.

[0082] Preferred, such as Figure 4 As shown, the top cover 20 is provided with several planting holes 21, and deep-rooted salt-tolerant plants are planted in the planting holes 21, including at least one of the following: Suaeda salsa, Suaeda salsa, Reed, Salicornia glutinosa, Deer antler velvet, Tamarix chinensis, and Elaeagnus angustifolia. Among them, the salt-tolerant plants with relatively long root systems planted on the ecological recharge well pond can penetrate into the pond through the planting holes 21 and enter the pond body 14 through transpiration, thereby helping to lower the water level of the salt water in the pond body 14 and reduce the salt content of the salt water in the pond body 14 (the salt-tolerant plants can absorb salt water through their roots and transfer the salt to their leaves or other parts for excretion, thus reducing the salt content of the salt water in the pond body 12 to a certain extent). At the same time, and importantly, the roots of these plants can continue to grow, attach to, and penetrate into the filter layer outside the well casing 15. They interact with microorganisms (mainly bacteria attached to the carrier ceramic particles) to form micropores, improving the structure of the filter layer, further preventing problems such as caking, ensuring the continuous filtration capacity of the multiple filter layers in the well tank of this invention, improving reliability, and reducing maintenance costs. Simultaneously, the plant roots can also provide effective attachment points for microorganisms, facilitating their further reproduction.

[0083] Preferred, such as Figure 4 As shown, the bottom of the top cover 20 is also connected to a hanging cage 22, which is filled with soil conditioner 23. When the soil conditioner 23 comes into contact with the rainwater, it undergoes continuous ion exchange, further reducing the sodium ion content in the rainwater while releasing a large number of active ingredients. These active ingredients (such as calcium and magnesium ions) can be released into the groundwater layer 2 along with the rainwater, and then diffuse into the surrounding soil, improving water quality, reducing soil alkalinity, reducing the possibility of soil salinization, and accelerating the ecological restoration process of saline-alkali land. After a certain period of use, the soil conditioner 23 needs to be removed from the hanging cage 22 and replaced with new soil conditioner 23 to ensure the soil improvement effect.

[0084] Preferably, the soil conditioner 23 includes at least one of crushed brick, fly ash, desulfurized gypsum, phosphogypsum, and lime. More preferably, it is crushed brick and / or fly ash, which, as construction / industrial waste, achieve soil improvement while also being relatively inexpensive.

[0085] Preferably, the high-salt recovery well pool includes a buffer pool for temporarily storing desalinated water with a salt concentration higher than a predetermined threshold, and an evaporation crystallization pool 24 for the desalinated water to evaporate and crystallize, connected in sequence. After the diversion module 13 discharges the desalinated water into the high-salt recovery well pool, this desalinated water is preferentially stored in the buffer pool and then gradually released into the evaporation crystallization pool 24 for crystallization, thus avoiding excessive desalinated water in the evaporation crystallization pool 24 that makes crystallization difficult.

[0086] Preferably, the buffer tank is a semi-underground or underground structure (i.e., buffer tanks are generally built underground) to ensure smooth water flow. The buffer tank is also lined with an aging-resistant geomembrane with a thickness of not less than 1.5 mm. The geomembranes are joined by hot-melt welding, with a weld strength of not less than 80% of the strength of the parent material. Preferably, the aging-resistant geomembrane has an aging resistance of at least 50 years for outdoor use, ensuring its seepage prevention and aging resistance in high-salt environments.

[0087] Preferably, the evaporation crystallization tank 24 is an above-ground or semi-underground structure. To ensure its evaporation crystallization effect, such as... Figure 5 As shown, a ground-level structure is preferred. When the evaporation crystallization tank 24 adopts a ground-level structure, a water pump can be used to connect the buffer tank and the evaporation crystallization tank 24, pumping the high-salinity desalinated water from the buffer tank to the evaporation crystallization tank 24. In this case, although a water pump is used, it is generally built above ground and only used for the transfer of small amounts of high-salinity desalinated water, so it is not prone to problems and the maintenance cost is low. Multiple buffer tanks can be connected to the same evaporation crystallization tank at the same time.

[0088] The crystalline salt precipitated in evaporation crystallization tank 24 can be collected periodically. After passing the test, it can be used as a snow melting agent or industrial raw material (such as raw material for chlor-alkali industry) for resource utilization and capital recovery.

[0089] Of course, a deeper semi-underground evaporation crystallization tank 24 can also be set up, and gravity (which requires the installation of water valves and other structures) can be used for transfer.

[0090] The top of the evaporation crystallization tank 24 is an open structure and is covered with a heat-insulating film 25 to increase the temperature inside the evaporation crystallization tank 24. The heat-insulating film 25 creates a greenhouse inside the evaporation crystallization tank 24, which accelerates the evaporation of water.

[0091] More preferably, the side of the evaporation crystallization tank 24 is provided with a water collection trough 26 and a water collection tank connected in sequence. The heat insulation membrane 25 is inclined, and its bottom end is located in the water collection trough 26. The water evaporated in the evaporation crystallization tank 24 condenses on the heat insulation membrane 25 and slides into the water collection trough 26 along the inclined angle of the heat insulation membrane 25, and then flows into the water collection tank, avoiding the backflow of evaporated water or waste of water resources. The water in the water collection tank can be directly discharged or used for the reserve water of the flushing subsystem (i.e., the recovered water of the above-mentioned high-salt recovery well pool), reducing the water demand of the salt discharge system of the present invention.

[0092] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0093] Example 1

[0094] This embodiment provides a subsurface pipe-recharge well system for desalination in inland saline-alkali land. The system is applied to a moderately saline-alkali land improvement project covering 100 mu (approximately 6.7 hectares). The soil is chloride-sulfate type saline soil, with an average salt content of 4.2 g / kg in the 0-30 cm soil layer, an alkalinity of 8%, poor soil permeability, and a pH of 8.9. Surveying revealed a continuously distributed clay impermeable layer with a top slab depth of 1.0 meter and a thickness of 1.8 meters, while the groundwater depth is 5.8 meters.

[0095] It includes: underground water collection and transportation system, pretreatment and diversion system, ecological recharge well pool system, and monitoring and control system.

[0096] The underground water collection and transportation system adopts a herringbone layout: First, a high-strength PVC-carbon fiber composite underground water collection pipe 27 with a diameter (DN) of 160mm and a single length of 6 meters is laid at a depth of 0.8 meters underground (above the clay layer) with a slope of 0.5%. The distribution density of the seepage holes (10mm in diameter) on the pipe wall increases from the venting end to the water outlet end, such as... Figure 6As shown, each water collection pipe 27 has a vent pipe 28 with a diameter of 20mm at its vent end to balance the initial air pressure; all water collection pipes 27 (spaced 20 meters apart) converge into a DN200 primary water supply pipe 3, which is a seamless pipe and is closed at its downstream end; multiple primary water supply pipes 3 then converge into a DN250 secondary water supply pipe 4, which is closed at its upstream starting end. A low-pressure node cavity is installed at the connection between each primary water supply pipe 3 and the secondary water supply pipe 4, with a throttling pipe 6 having a diameter of 100mm (0.4 times the diameter of the secondary water supply pipe 4) and a length of 200mm (0.8 times the diameter of the secondary pipe). The end of the secondary water supply pipe 4 is connected to a siphon reinforcement pipe 8 with a vertical drop of 0.8 meters and a slope of 2%. At the initial closed end of the secondary pipe, a flushing subsystem is connected, such as... Figure 7 As shown, the flushing subsystem includes a 5-cubic-meter clean water tank 29 (the water source is recycled condensate) and a small booster pump 30 for system maintenance flushing.

[0097] In the pretreatment and diversion system, pretreatment chamber 9 is an underground concrete structure with dimensions of 2.0 × 1.5 × 1.8 m (length × width × height). After entering the chamber, the desalinated water first undergoes coarse filtration through a retractable stainless steel grid with a 5 mm aperture, placed at a 60-degree angle. It then flows into a zeolite adsorption layer 11, which is 2.0 meters long and filled with NaOH-activated modified zeolite, for ion exchange to remove sodium ions. Finally, it flows through an online conductivity sensor (range 0-20 mS / cm). Sensor data is transmitted to the monitoring and control system in real time. When the reading exceeds the set threshold of 5.0 mS / cm, the control system instructs the electric three-way valve to activate, diverting the high-salinity desalinated water.

[0098] In the ecological recharge well system, the ecological recharge well is a semi-underground reinforced concrete structure (4×3×2.5m in size), lined with a 1.5mm thick high-density polyethylene geomembrane. A sand filter well 1 (well pipe 15 with a diameter of DN250) is located in the center of the bottom of the pool. Its filter layer consists of a gravel layer (particle size 10-20mm, thickness 200mm), a coarse sand layer (particle size 2-5mm, thickness 250mm), a layer of bacteria-laden ceramic particles (particle size 5-10mm, thickness 200mm, loaded with Bacillus subtilis and Bacillus licheniformis), and a fine sand layer (particle size 0.5-1mm, thickness 150mm). The top cover 20 has reserved planting holes 21 for cultivating Suaeda salsa, and a hanging cage 22 containing modified phosphogypsum granules and soil conditioner 23 is suspended. The high-salt recovery well pool includes an underground buffer pool with a volume of 30 cubic meters and an above-ground evaporation and crystallization pool 24 with an area of ​​50 square meters. The buffer pool and the evaporation and crystallization pool 24 are gradually connected by a water pump. The evaporation and crystallization pool 24 is covered with a transparent heat-insulating membrane 25 to accelerate evaporation and recover condensate.

[0099] After 24 months of continuous operation, the system demonstrated outstanding overall performance. During operation, the peak discharge flow rate remained stable at 1.4 m³ / s. 3 The average salinity of the 0-30 cm soil layer decreased from 4.2 g / kg to 1.1 g / kg per hour, achieving a desalination rate of 64%. 85% of the desalinated water met standards after pretreatment and was safely reinjected into groundwater bodies, with no abnormal increase in salinity observed in the surrounding groundwater after reinjection. The remaining 15% of the desalinated water was recycled, with an annual recovery of 2.1 tons of crystalline salt (mainly NaCl and Na2SO4). No manual maintenance was performed during the operation of the desalination system (only periodic replacement of soil conditioner 23). The flushing subsystem operated stably without any blockages or other problems. No signs of compaction were observed in any of the filter layers within sand filter well 1, and the survival rate of the planted Suaeda salsa reached 95%, exhibiting vigorous growth. The activity of microorganisms around the well was significantly enhanced, demonstrating a good ecological restoration effect.

[0100] Example 2

[0101] This embodiment provides a subsurface pipe-recharge well pool salt drainage system for inland saline-alkali land. The salt drainage system targets 100 mu of severely alkaline saline soil with an average soil salt content of 6.8 g / kg, pH value of 9.5, alkalinity of 20%, clay layer top slab buried at a depth of 1.2 meters and a thickness of 2.0 meters, and groundwater mineralization of 4.5 g / L.

[0102] Based on actual conditions, the salt removal system was adapted and modified from Example 1. In the underground water collection and transportation system, the spacing between the underground water collection pipes was increased to 15 meters to enhance the salt washing intensity. The pretreatment and diversion system uses a 5-meter-long medium zeolite adsorption layer 11. The thickness of the bacterial-carrying ceramsite layer in the ecological recharge well was increased to 300 mm, and the soil conditioner 23 in the cage 22 was replaced with a mixture of desulfurized gypsum and fly ash (1:1) to specifically provide calcium ions to replace sodium ions in the soil.

[0103] After 18 months of stable operation, the desalination system reduced soil salinity to 2.2 g / kg, soil pH from 9.5 to 8.3, and ESP from 18% to 9%, demonstrating a good effect on improving alkaline soil. After the desalination was reinjected, the salinity of surrounding groundwater did not show an abnormal increase. Furthermore, due to the high initial salinity, 30% of the desalinated water was diverted to the high-salinity recovery wells, resulting in an annual recovery of 5.5 tons of crystalline salt, further demonstrating significant benefits. Within a 100-meter radius of the ecological reinjection wells, the soil microbial community diversity index increased by more than 30%, and vegetation cover significantly increased, achieving an ecological restoration effect.

[0104] Example 3

[0105] This embodiment provides a subsurface pipe-recharge well system for desalination in inland saline-alkali land. The target area of ​​this system is 80 mu (approximately 5.3 hectares) of soda saline-alkali land. The difference from Embodiment 1 is that the soil salinity is only 3.0 g / kg, but the pH value is as high as 10.1, and the alkalinity is 25%. The top layer of clay is buried at a depth of 0.9 meters and has a thickness of 1.5 meters. The groundwater level is relatively shallow at 4.0 meters, and there is a seasonally frozen soil layer in the area, resulting in cold winters.

[0106] Adapted to local conditions, the underground water collection pipes and primary / secondary underground water transmission pipes are laid at depths below the local frost line (>1.2 meters) to prevent frost heave damage. Due to the shallow clay layer, the water collection and transmission system can only be laid within the clay layer due to frost constraints; therefore, the laying slope has been adjusted to 0.8%, and the vertical drop of the siphon reinforcement pipe 8 has been increased to 1.0 meter. Additionally, a soil temperature sensor (connected to the monitoring and control system) has been added. When prolonged low temperatures are predicted, the desalination system can empty the pipes to prevent residual water from freezing.

[0107] After two complete freeze-thaw cycles (24 months), the desalination system of this embodiment demonstrated excellent reliability. Soil pH decreased to 8.5, and alkalinity decreased from 25% to 12%, fundamentally improving soil chemical properties. No damage caused by frost heave or additional maintenance due to climate or soil conditions occurred during operation. The system could start immediately after spring warming, responding quickly and exhibiting high environmental adaptability. Even with a steeper slope and enhanced siphon effect, drainage efficiency still reached over 90% of that of Example 1.

[0108] In summary, the present invention can solve the technical problems of existing salt drainage systems, such as poor adaptability to clay soil areas, low drainage efficiency, high operation and maintenance costs, and easy generation of secondary pollution.

[0109] 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A submerged pipe-reinjection well system for desalination in inland saline-alkali land, characterized in that, include: The monitoring and control system, along with the sequentially connected underground pipe water collection and transportation system, pretreatment and diversion system, and ecological recharge well pool system; The monitoring and control system is used to detect and control the operating status of other systems; the underground pipe water collection and transportation system is used to collect saline water in the soil and transport it to the pretreatment and diversion system; the pretreatment and diversion system is used to desalinate the saline water transported by the underground pipe water collection and transportation system, reduce its salt content, and divert it according to the salt concentration of the pretreated saline water; the ecological recharge well system is used to receive the saline water produced by the pretreatment and diversion system and perform ecological recharge and / or reuse. The ecological recharge well system includes an ecological recharge well that receives salt water with a salt concentration below a predetermined threshold and a high-salt recovery well that receives salt water with a salt concentration above a predetermined threshold; the ecological recharge well is equipped with a sand filter well (1), which is connected to the groundwater layer (2).

2. The inland saline-alkali land underground pipe-reinjection well salt drainage system as described in claim 1, characterized in that, The underground water collection and transportation system includes several pipe network subsystems; each of the pipe network subsystems includes several underground water collection pipes, multiple primary underground water transmission pipes (3) and secondary underground water transmission pipes (4); several seepage outlets are provided on the pipe wall of the underground water collection pipes; the underground water collection pipes, primary underground water transmission pipes (3) and secondary underground water transmission pipes (4) are all inclined, with a slope of 0.2%-0.6%; several underground water collection pipes are connected to one primary underground water transmission pipe (3); multiple primary underground water transmission pipes (3) are connected to the secondary underground water transmission pipes (4); The secondary water supply pipe (4) is also provided with a low-pressure node cavity for enhancing the low-pressure environment inside the primary water supply pipe (3); along the direction of brine flow in the secondary water supply pipe (4), the low-pressure node cavity includes a constriction cone (5), a throttling pipe (6) and a diffusion cone (7); the primary water supply pipe (3) is connected to the side wall of the throttling pipe (6) in the low-pressure node cavity.

3. The inland saline-alkali land underground pipe-reinjection well salt drainage system as described in claim 2, characterized in that, The water collection pipe has a ventilation end and a water outlet end at its two ends; the water outlet end is connected to the primary delivery pipe; the ventilation end is connected to a ventilation pipe, the outlet of which is higher than the ground surface and connected to the outside; the diameter of the outlet of the ventilation pipe does not exceed 20% of the diameter of the water collection pipe. The outlet of the primary water supply pipe (3) is equipped with a flow meter, which is used to monitor the flow rate of the brine output by the primary water supply pipe (3); the outlet of the secondary water supply pipe (4) is equipped with a flow regulating valve; both the flow meter and the flow regulating valve are connected to the monitoring and control system; the outlet of the secondary water supply pipe (4) is connected to the pretreatment and diversion system.

4. The inland saline-alkali land underground pipe-reinjection well pool salt drainage system as described in claim 2 or 3, characterized in that, The underground water collection and transportation system also includes a flushing subsystem; the flushing subsystem is connected to the relatively high end of the secondary water conveyance underground pipe (4) and is used to inject clean water into the secondary water conveyance underground pipe (4).

5. The inland saline-alkali land underground pipe-reinjection well salt drainage system as described in claim 1, characterized in that, The pretreatment and diversion system includes a pretreatment chamber (9) and a diversion module (13); the inlet of the pretreatment chamber (9) is connected to the underground pipe water collection and transportation system; inside the pretreatment chamber (9), a coarse filter screen (10), a zeolite adsorption layer (11) and a water quality monitoring unit (12) are arranged sequentially along the brine flow direction; the water quality monitoring unit (12) is used to monitor the salt concentration of the brine after passing through the zeolite adsorption layer (11); the outlet of the pretreatment chamber (9) is connected to the diversion module (13); the diversion module (13) diverts the brine according to the monitoring results of the water quality monitoring unit (12); both the water quality monitoring unit (12) and the diversion module (13) are communicatively connected to the monitoring and control system.

6. The inland saline-alkali land underground pipe-reinjection well salt drainage system as described in claim 5, characterized in that, The mesh size of the grid filter is 3-8mm; the grid filter is inclined toward the inlet direction away from the pretreatment chamber (9) so that the angle between it and the horizontal plane is 45-75 degrees; the zeolite in the zeolite filter layer is modified activated zeolite; the diversion module (13) includes a multi-way valve.

7. The inland saline-alkali land underground pipe-reinjection well salt drainage system as described in claim 1, characterized in that, The ecological recharge well pool includes a pool body (14); the pool body (14) is a semi-underground structure with a top cover (20) on its top; the sand filter well (1) is located at the bottom of the pool body (14).

8. The inland saline-alkali land underground pipe-reinjection well pool salt drainage system as described in claim 7, characterized in that, The sand filter well (1) includes a well pipe (15) and a fine sand filter layer (16), a bacteria-carrying ceramic particle filter layer (17), a coarse sand filter layer (18), and a gravel filter layer (19) sequentially covering the outer periphery of the well pipe (15). The thickness of each filter layer is 150-300mm. The well pipe (15) includes a filter section and a conveying section. The filter section is located in the pool body (14). The conveying section passes through the bottom of the pool body (14) and communicates with the groundwater layer (2). The filter section of the well pipe (15) is provided with filter holes for collecting water filtered by the fine sand filter layer (16), the bacteria-carrying ceramic particle filter layer (17), the coarse sand filter layer (18), and the gravel filter layer (19). The porosity of the filter pores on the filter section is 15-20%; the pore size of the filter pores is smaller than the minimum particle size of the fine sand in the fine sand filter layer. The particle size of the bacterial-loaded ceramic granule layer is 5-10 mm, and the porosity is not less than 30%; the bacterial-loaded ceramic granule layer is loaded with salt-tolerant bacteria for removing organic pollutants from brine.

9. The inland saline-alkali land underground pipe-reinjection well salt drainage system as described in claim 7, characterized in that, The top cover (20) is provided with several planting holes (21), and deep-rooted salt-tolerant plants are planted in the planting holes (21), including at least one of Suaeda salsa, Suaeda salsa, Reed, Salicornia glutinosa, Deer antler velvet, Tamarix chinensis and Elaeagnus angustifolia. The roots of the deep-rooted salt-tolerant plants are located in the fine sand filter layer (16), the bacterial ceramsite filter layer (17), the coarse sand filter layer (18) and the gravel filter layer (19). The bottom of the top cover (20) is also connected to a hanging cage (22), which is filled with soil conditioner (23). The soil conditioner (23) includes at least one of crushed brick, fly ash, desulfurized gypsum, phosphogypsum and lime.

10. The inland saline-alkali land underground pipe-reinjection well salt drainage system as described in claim 1, characterized in that, The high-salt recovery well pool includes a buffer pool for temporarily storing brine with a salt concentration higher than a predetermined threshold and an evaporation crystallization pool (24) connected in sequence; the top of the evaporation crystallization pool (24) is covered with a heat-insulating membrane (25) for increasing the temperature inside the evaporation crystallization pool (24); the heat-insulating membrane (25) is inclined.

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