A system and method for co-treatment of landfill leachate and shale gas wastewater

Abstract

The application discloses a kind of garbage leachate and shale gas wastewater collaborative treatment system and processing method, belong to wastewater treatment technical field, the system includes sequentially connected wastewater collaborative pre-mixing unit, depth purification unit and membrane distillation concentration unit.The core step of method is: first, two kinds of wastewater are transported to collaborative reactor and mixed according to specific volume ratio, reduce pollution load using the interaction of its internal components;Mixed solution is purified after zeolite adsorption and iron salt / sulfite fenton oxidation, into membrane distillation module to realize efficient desalination and water resource recovery.The application is combined by waste treatment and waste treatment, and the influence of front-end pre-mixing collaborative reaction on subsequent treatment unit is reduced, the technical problems such as process complexity, high cost and membrane fouling are effectively solved when two kinds of wastewater are treated separately, efficient purification and stable operation of difficult-to-treat wastewater are realized, and the water quality is excellent.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and in particular to a co-treatment system and method for landfill leachate and shale gas wastewater. Background Technology

[0002] Landfill leachate is a toxic and harmful organic wastewater formed during the processes of landfilling, fermentation, and other waste disposal. It is produced by the water content of the waste itself, combined with the infiltration and scouring of external water sources such as rainwater, surface water, and groundwater. With industrial development, the amount of solid waste landfilled has increased significantly, leading to a large-scale generation of landfill leachate. This leachate is complex in quality, typically containing high concentrations of COD, sulfates, ammonia nitrogen, and various metal ions, making it difficult to treat. Shale gas wastewater, on the other hand, is high-salt wastewater generated during shale gas extraction. It is produced when water used in drilling and hydraulic fracturing processes is returned to the surface in a contaminated form after extraction. Currently, due to the increasing maturity of extraction technology and the valuable unconventional natural gas energy source of shale gas, global shale gas extraction is booming, resulting in the discharge of large amounts of shale gas wastewater. This wastewater is typically rich in various inorganic scaling ions, suspended solids, and organic pollutants. If discharged directly without proper treatment, it will inevitably cause serious environmental pollution.

[0003] Currently, the treatment of these two types of wastewater mostly employs independent process routes. For landfill leachate, a combined process of "biological treatment + advanced oxidation + membrane treatment" is often used, but this process is lengthy, consumes high amounts of chemicals, and the resulting concentrate is difficult to dispose of. For shale gas wastewater, a process of "coagulation sedimentation + softening + membrane concentration (such as reverse osmosis) + evaporation crystallization" is often used, which has extremely high energy consumption and serious membrane scaling and fouling problems. Treating these two types of wastewater separately is technically complex and costly. In recent years, some studies have proposed a synergistic treatment approach of "treating waste with waste" by utilizing the characteristics of different wastewaters, but this approach remains largely at the laboratory stage, lacking an integrated engineering system that can achieve stable, efficient, and resource-recoverable treatment.

[0004] Based on these issues, a system that can fully leverage the synergistic effect of the two types of wastewater and couple a highly efficient deep purification and desalination unit is proposed, which is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a co-treatment system and method for landfill leachate and shale gas wastewater to solve the problems in the background art.

[0006] To achieve the above objectives, the present invention provides a co-treatment system for landfill leachate and shale gas wastewater, comprising a premixing unit, a deep purification unit, and a membrane distillation unit connected sequentially by pipelines. The premixing unit includes a first raw water tank, a second raw water tank, a premixing reactor, and a first intermediate water tank. The deep purification unit includes a sequential adsorption-advanced oxidation reactor and a second intermediate water tank. The membrane distillation unit includes a heater, a membrane distillation reactor, a condenser, and a collection tank. The first intermediate water tank is connected to the sequential adsorption-advanced oxidation reactor, and the second intermediate water tank is connected to the heater.

[0007] Preferably, the outlets of the first raw water tank and the second raw water tank are respectively connected to the inlet of the premixing reactor through a first inlet gear pump and a second inlet gear pump; an automatic flow regulating component is provided between the first raw water tank and the first inlet gear pump, and between the second raw water tank and the second inlet gear pump; The automatic flow regulation component includes an online flow meter, an inlet valve, and a controller.

[0008] Preferably, the outlet of the premixing reactor is connected to the first intermediate water tank in sequence through a first outlet valve and a first outlet gear pump, and a stirring assembly is provided inside the premixing reactor.

[0009] Preferably, a first inlet valve and a third inlet gear pump are sequentially arranged between the first intermediate water tank and the sequential adsorption-advanced oxidation reactor; a second outlet valve and a second outlet gear pump are sequentially arranged between the sequential adsorption-advanced oxidation reactor and the second intermediate water tank.

[0010] Preferably, the sequential adsorption-advanced oxidation reactor includes an adsorption unit and an advanced oxidation unit connected in series. The adsorption unit is filled with zeolite, and the advanced oxidation unit is equipped with a dosing assembly for adding iron salts and sulfites.

[0011] Preferably, the inner cavity of the adsorption device is arranged from top to bottom as follows: a water distributor, a coarse filter layer, a zeolite adsorption layer, and a powder interception layer. An inlet is located at the top of the adsorption device for receiving wastewater flowing from the pool. The top cover of the adsorption device is a quick-opening, sealing cover for rapid replacement of the zeolite adsorption layer and the powder interception layer. A pressure gauge is installed at the inlet of the adsorption device to monitor the operating pressure in real time, determine the degree of blockage in the adsorption layer through pressure difference, and guide the backwashing and filter layer replacement process. An outlet is located at the bottom of the adsorption device, discharging the treated wastewater through a check valve into the next advanced oxidation device. A sampling port is also located at the outlet to monitor the ammonia nitrogen concentration in the effluent and promptly determine whether the zeolite is saturated. An exhaust valve is installed on the side wall of the adsorption device, located on the side of the powder interception layer, to prevent air accumulation inside the device and ensure water flow distribution and adsorption efficiency. This valve is mainly used during equipment startup and backwashing. The water distributor ensures that the incoming peak water flow passes evenly through the adsorption layer, avoiding local short circuits that could lead to insufficient ammonia nitrogen adsorption. The coarse filter layer contains quartz sand to intercept large particles of impurities, preventing pore blockage in the zeolite adsorption layer and extending the adsorption cycle. The zeolite adsorption filter layer is used to adsorb ammonia nitrogen, reducing its impact on subsequent membrane distillation treatment. The powder interception layer consists of a stainless steel filter screen and PP cotton to prevent zeolite powder loss, ensuring effluent water quality and adsorbent utilization.

[0012] Preferably, the advanced oxidation device is configured from top to bottom as an advanced oxidation reaction chamber, an inclined tube sedimentation chamber, and a sludge collection hopper. The advanced oxidation reaction chamber is used for Fenton-like oxidation of wastewater. A stirring component is installed in the advanced oxidation reaction chamber to ensure that the reactants are fully mixed. A dosing component and a nitrogen pipe are installed at the upper end of the advanced oxidation reaction chamber. The dosing component includes a ferrous sulfate dosing tank and a sodium sulfite dosing tank. The nitrogen pipe is used to remove oxygen from the wastewater to prevent ferrous ions from being prematurely oxidized to ferric iron. An advanced oxidation inlet is provided on the side wall of the advanced oxidation reaction chamber, which is connected to the bottom outlet of the adsorption device. The inclined tube sedimentation chamber is used to separate iron sludge from water after the Fenton-like reaction. An outlet is set on the side wall of the inclined tube sedimentation chamber to transport the supernatant of the inclined tube sedimentation chamber to the effluent pipe. The bottom sludge collection hopper is responsible for concentrating and storing iron sludge, and a sludge discharge valve is set at the lower end of the sludge collection hopper to discharge sludge after the process is completed.

[0013] Preferably, the outlet of the second intermediate water tank is connected to the heater in sequence via a second inlet valve and a fourth inlet gear pump. The outlet of the heater is connected to the hot-side inlet of the membrane distillation reactor. The hot-side concentrate outlet of the membrane distillation reactor is returned to the second intermediate water tank through a concentrate circulation pipeline. The cold-side outlet of the membrane distillation reactor is connected to the collection tank in sequence via a third outlet valve, a third outlet gear pump, and a condenser.

[0014] The present invention also provides a treatment method based on the above-mentioned co-treatment system for landfill leachate and shale gas wastewater, comprising the following steps: S1. Co-mixing: Landfill leachate from the first raw water tank and shale gas wastewater from the second raw water tank are transported to the premixing reactor at a predetermined volume ratio. During this process, two automatic flow control components are used to precisely control the mixing ratio. After the two types of wastewater enter the premixing reactor, they are fully mixed and reacted under stirring conditions. The interaction between organic components and inorganic ions in the two types of wastewater generates low-pollution intermediate products and flocculants. After the reaction, the mixture is allowed to stand to achieve solid-liquid separation, and the supernatant enters the first intermediate water tank. S2. Deep purification: The supernatant in the first intermediate water tank is pumped into a sequential adsorption-advanced oxidation reactor. First, the residual ammonia nitrogen and other inorganic pollutants are removed by the zeolite adsorption device. Then, it enters the advanced oxidation device, where iron salts and sulfites are added to carry out a Fenton-like oxidation reaction to deeply degrade the recalcitrant organic matter. The effluent enters the second intermediate water tank. S3. Membrane distillation desalination and concentration: The effluent from the second intermediate water tank is heated to 60~80℃ by a heater and then sent to the hot side of the membrane distillation reactor. Driven by the vapor pressure difference on both sides of the membrane, water vapor passes through the membrane pores, and the distilled water enters the condenser and is condensed into high-quality product water, which is collected in the product water collection unit. The hot side concentrate is returned to the second intermediate water tank through the concentrate circulation pipeline.

[0015] Preferably, in step S1, the volume ratio of landfill leachate to shale gas wastewater is (15~19):(1~5).

[0016] Preferably, in step S2, the zeolite dosage in the adsorption device is 100-150 g / L, and the iron salt and sulfite dosage in the advanced oxidation device are both 8-12 mmol / L.

[0017] Preferably, in step S3, the membrane distillation reactor uses a hydrophobic microporous membrane, and the material of the hydrophobic microporous membrane is one of polyvinylidene fluoride, polytetrafluoroethylene, polypropylene, modified polysulfone, modified polyethersulfone, and cellulose ester membrane.

[0018] Therefore, the co-treatment system and method for landfill leachate and shale gas wastewater of the present invention have the following beneficial effects: (1) By mixing the two types of wastewater in an optimized ratio, the organic matter concentration, hardness and scaling tendency of the mixed wastewater are significantly reduced by utilizing their own components to undergo physicochemical reactions, thereby reducing the reagent consumption and treatment load of the subsequent deep purification unit.

[0019] (2) The combination of zeolite adsorption and FeSO4 / Na2SO3-like Fenton oxidation is used as a pretreatment before membrane distillation. Zeolite first adsorbs ammonia nitrogen and other inorganic pollutants, creating better conditions for subsequent oxidation; while Fenton oxidation targets recalcitrant organic matter. The synergistic effect of the two reduces the risk of volatile migration and organic and inorganic pollution, providing high-quality feed water with low pollution and low scaling risk for membrane distillation, and greatly alleviating membrane fouling.

[0020] (3) This invention organically integrates synergistic pretreatment, deep purification and thermal membrane distillation into a continuous system. The membrane distillation process can almost completely retain all ions, organic matter and pathogenic microorganisms, producing water of extremely high quality and enabling a high proportion of water resource recovery. The concentrate circulation design improves the efficiency of thermal energy utilization.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the processing system structure according to an embodiment of the present invention; Figure 2 The diagram shows a comparison of the performance improvement of the embodiments of the present invention, where (a) represents membrane flux and (b) represents conductivity. Figure 3 This is a schematic diagram of the adsorption device structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the advanced oxidation apparatus according to an embodiment of the present invention; Figure label: 1. First raw water tank; 2. Second raw water tank; 3. Premixing reactor; 4. First intermediate water tank; 5. First inlet gear pump; 6. Second inlet gear pump; 7. Automatic flow regulation assembly; 8. Adsorption device; 81. Water distributor; 82. Coarse filter layer; 83. Zeolite adsorption layer; 84. Powder interception layer; 85. Inlet; 86. Quick-opening sealing top cover; 87. Pressure gauge; 88. Outlet; 89. Sampling port; 810. Exhaust valve; 9. First outlet valve; 10. First outlet gear pump; 11. Advanced oxidation device; 111. Advanced oxidation reaction chamber; 112. Inclined... 113. Tube sedimentation chamber; 114. Sludge collection hopper; 115. Stirring assembly; 116. Nitrogen pipe; 117. Ferrous sulfate dosing tank; 118. Sodium sulfite dosing tank; 119. Advanced oxidation inlet; 12. Outlet; 13. Second intermediate water tank; 14. First inlet valve; 15. Third inlet gear pump; 16. Second outlet valve; 17. Heater; 18. Membrane distillation reactor; 19. Condenser; 20. Collection tank; 21. Second inlet valve; 22. Fourth inlet gear pump; 23. Third outlet valve; 24. Third outlet gear pump. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0025] like Figure 1 As shown, this invention provides a co-treatment system for landfill leachate and shale gas wastewater, comprising a premixing unit, a deep purification unit, and a membrane distillation unit connected sequentially via pipelines. The premixing unit includes a first raw water tank 1, a second raw water tank 2, a premixing reactor 3, and a first intermediate water tank 4. The first raw water tank 1 and the second raw water tank 2 are respectively filled with landfill leachate and shale gas wastewater. The outlets of the first raw water tank 1 and the second raw water tank 2 are respectively connected to the inlet of the premixing reactor 3 via a first inlet gear pump 5 and a second inlet gear pump 6. An automatic flow regulating component 7 is installed between the first raw water tank 1 and the first inlet gear pump 5, and between the second raw water tank 2 and the second inlet gear pump 6. The automatic flow regulating component includes an online flow meter, an inlet valve, and a programmable logic controller, thereby achieving precise control of the mixing ratio. The outlet of the premixing reactor 3 is connected to the first intermediate water tank 4 in sequence through the first outlet valve 9 and the first outlet gear pump 10. The premixing reactor 3 is equipped with a stirring assembly, which enables the two types of wastewater to be fully mixed.

[0026] In the premixing unit, the landfill leachate in the first raw water tank 1 enters the premixing reactor 3 after the flow rate is controlled by the automatic flow regulating component 7 and the first inlet gear pump 5. The shale gas wastewater in the second raw water tank 2 enters the premixing reactor 3 after the flow rate is controlled by the automatic flow regulating component 7 and the second inlet gear pump 6. The landfill leachate and shale gas wastewater are stirred and mixed in the premixing reactor 3. The inorganic ions in the two wastewaters interact to generate flocculent precipitates, represented by barium sulfate. These substances co-precipitate with various inorganic ions and organic groups through polar adsorption, hydrogen bonding, and other interactions, effectively purifying the water. At the same time, the organic matter in the two wastewaters also reacts with each other to produce low-pollution organic matter, reducing the pollution risk of subsequent steps.

[0027] In this process, the mixing ratio of the two wastewaters is controlled by the automatic flow regulation component 7 and the inlet gear pump. This can prevent the excessive addition of shale gas wastewater (high inorganic ion content) during the mixing process from generating too much highly polluting inorganic scaling, thus ensuring that the mixing process produces a positive overall effect.

[0028] After premixing, the wastewater is transported from the outlet of the premixing reactor 3 to the first intermediate water tank 4 via the first outlet valve 9 and the first outlet gear pump 10 for intermediate collection. The deep purification unit includes a sequential adsorption-advanced oxidation reactor and a second intermediate water tank 12; the outlet of the first intermediate water tank 4 is connected to the inlet of the sequential adsorption-advanced oxidation reactor; a first inlet valve 13 and a third inlet gear pump 14 are sequentially arranged between the outlet of the first intermediate water tank 4 and the inlet of the sequential adsorption-advanced oxidation reactor.

[0029] The drain outlet of the sequential adsorption-advanced oxidation reactor is connected to the second intermediate water tank 12. A second effluent valve 15 and a second effluent gear pump 16 are sequentially installed between the sequential adsorption-advanced oxidation reactor and the second intermediate water tank 12.

[0030] The sequential adsorption-advanced oxidation reactor comprises an integrated adsorption unit 8 and an advanced oxidation unit 11 connected in series. For example... Figure 3 As shown, the inner cavity of the adsorption device 8 is arranged from top to bottom as follows: a water distributor 81, a coarse filter layer 82, a zeolite adsorption layer 83, and a powder interception layer 84. The water distributor 81 ensures that the incoming peak water flow passes evenly through the zeolite adsorption layer 83, avoiding local short circuits that could lead to insufficient ammonia nitrogen adsorption. The coarse filter layer 82 contains quartz sand to intercept large particles of impurities, preventing pore blockage of the zeolite adsorption layer and extending the adsorption cycle. The zeolite adsorption layer 83 is used to adsorb ammonia nitrogen, reducing its impact on subsequent membrane distillation treatment. The powder interception layer 84 is composed of a stainless steel filter screen and PP cotton, used to prevent zeolite powder loss, ensuring the quality of the effluent and the utilization rate of the adsorbent.

[0031] The adsorption device 8 is equipped with an inlet 85 at the top for receiving wastewater from the pool. The top cover of the adsorption device 8 is a quick-opening sealing cover 86 for rapid replacement of the zeolite adsorption layer and the powder interception layer. A pressure gauge 87 is installed at the inlet of the adsorption device 8 to monitor the operating pressure in real time, determine the degree of blockage in the adsorption layer through pressure difference, and guide the backwashing and filter replacement process. The bottom outlet of the adsorption device 8 is equipped with a bottom outlet 88, through which the treated wastewater passes through a check valve into the next advanced oxidation device 11. A sampling port 89 is installed at the outlet 88 to monitor the ammonia nitrogen concentration in the effluent and promptly determine whether the zeolite is saturated. An exhaust valve 810 is installed on the side wall of the adsorption device 8, located next to the powder interception layer 84, to prevent air accumulation and air resistance within the device, ensuring water flow distribution and adsorption efficiency. This valve is mainly used during equipment startup and backwashing.

[0032] like Figure 4As shown, the advanced oxidation device 11 is configured from top to bottom as an advanced oxidation reaction chamber 111, an inclined tube sedimentation chamber 112, and a sludge collection hopper 113. The advanced oxidation reaction chamber 111 is used to carry out a Fenton-like oxidation reaction of wastewater. A stirring assembly 114 is installed in the advanced oxidation reaction chamber 111 to ensure that the reactants are fully mixed. A dosing assembly and a nitrogen pipe 115 are installed at the upper end of the advanced oxidation reaction chamber 111. The dosing assembly includes a ferrous sulfate dosing tank 116 and a sodium sulfite dosing tank 117. The nitrogen pipe 115 is used to remove oxygen from the wastewater to prevent ferrous ions from being prematurely oxidized to ferric iron.

[0033] An advanced oxidation inlet 118 is provided on the side wall of the advanced oxidation reaction chamber 111, which is connected to the bottom outlet of the adsorption device 8.

[0034] The inclined tube sedimentation chamber 112 is used to separate iron sludge from water after the Fenton-like reaction. An outlet 119 is provided on the side wall of the inclined tube sedimentation chamber 112 to transport the supernatant of the inclined tube sedimentation chamber 112 to the effluent pipe. The bottom sludge collection hopper 113 is responsible for concentrating and storing iron sludge, and a sludge discharge valve is provided at the lower end of the sludge collection hopper 113 to discharge sludge after the process is completed.

[0035] In the entire deep purification unit, the effluent from the premixing unit is used as the influent. The wastewater in the first intermediate water tank 4 is transported into the sequential adsorption-advanced oxidation reactor through the first influent valve 13 and the third influent gear pump 14. Ammonia nitrogen and various organic substances are fully removed through zeolite adsorption and Fenton-like oxidation. The purified wastewater is then transported to the second intermediate water tank 12 for collection through the second effluent valve 15 and the second effluent gear pump 16. This process greatly alleviates the pressure on the subsequent membrane distillation treatment.

[0036] The membrane distillation unit includes a heater 17, a membrane distillation reactor 18, a condenser 19, and a collection tank 20. A first intermediate water tank 4 is connected to a sequential adsorption-advanced oxidation reactor, and a second intermediate water tank 12 is connected to the heater 17. The outlet of the second intermediate water tank 12 is connected to the inlet of the heater 17 sequentially via a second inlet valve 21 and a fourth inlet gear pump 22. Wastewater from the second intermediate water tank 12 is transported to the heater 17 through the second inlet valve 21 and the fourth inlet gear pump 22, where it is heated to a temperature of 60-80°C.

[0037] The outlet of heater 17 is connected to the hot-side inlet of membrane distillation reactor 18. The heated wastewater enters membrane distillation reactor 18 for membrane distillation treatment. The hot-side concentrate outlet of membrane distillation reactor 18 is returned to the second intermediate water tank 12 through the concentrate circulation pipeline to maintain the temperature and concentration of the hot-side feed liquid and improve the heat utilization rate.

[0038] The cold-side outlet of the membrane distillation reactor 18 is connected to the collection tank 20 via a third outlet valve 23, a third outlet gear pump 24, a condenser 19, and a circulating cooling water system. The generated steam enters the condenser 19 for condensation, and the permeate is collected in the collection tank 20. In the membrane distillation unit, the treated wastewater undergoes final advanced treatment, and high-quality freshwater is produced by driving the temperature difference between heating and condensation.

[0039] The above treatment system will be further explained below with specific examples. The leachate used in the following embodiments and comparative examples is raw leachate water obtained from a landfill in Shenzhen. After filtration through qualitative filter paper with a pore size of 12μm, the turbidity is 8.62 NTU and the UV254 is 11.46 cm⁻¹. -1 COD was 1768 mg / L, TDS was 7370 mg / L, and NH4-N and Mg were present. 2+ Ca 2+ Ba 2+ and SO4 2- The concentrations were 1500, 30.06, 60.04, 0.47, and 1888 mg / L, respectively; the shale gas wastewater was the backflow wastewater from a shale gas well in the Sichuan Basin, and after filtration through a 12 μm pore size qualitative filter paper, the turbidity was 11.61 NTU, and the UV254 was 0.15 cm⁻¹. -1 COD was 1576 mg / L, TDS was 16445 mg / L, and NH4-N and Mg were present. 2+ Ca 2+ Ba 2+ and SO4 2- The concentrations were 126.5 mg / L, 29.42 mg / L, 305.78 mg / L, 305.91 mg / L and 45.66 mg / L, respectively.

[0040] The membrane modules in membrane distillation reactor 18 use hydrophobic polyvinylidene fluoride (PVDF) membranes with a pore size of 0.45 μm, and the effective membrane area is 10 cm². 2 The temperature difference is 70℃ The temperature is 20℃, and the influent and effluent flow velocities are 0.1 m / s. The membrane module consists of two units, each with a flow channel that is 5 cm long, 2 cm wide, and 0.5 cm deep. The feed side of the membrane module is located above the membrane, while the permeate side is located below the membrane.

[0041] Example 1 This embodiment uses the above-mentioned treatment system to treat landfill leachate and shale gas wastewater. The specific steps are as follows: S1. Collaborative premixing: The landfill leachate in the first raw water tank 1 is pumped into the premixing reactor 3 by the flow rate controlled by the automatic flow regulating component 7 and the first inlet gear pump 5. The shale gas wastewater in the second raw water tank 2 is pumped into the premixing reactor 3 by the flow rate controlled by the automatic flow regulating component 7 and the second inlet gear pump 6. The volume ratio of the two is 19:1. Then, the mixture and reaction are carried out under stirring. First, the two wastewaters are stirred at 100 r / min for 1 min to ensure that they are fully mixed. Then, the mixture is stirred at 40 r / min for 3 h to ensure that the wastewater quality is fully stabilized. The interaction between the organic components and inorganic ions in the two phases of wastewater is used to generate low-pollution intermediate products and flocculants. After the reaction, the mixture is allowed to stand and separate. The supernatant is pumped into the first intermediate water tank 4 through the first outlet valve 9 and the first outlet gear pump 10. S2. Deep purification: The supernatant in the first intermediate water tank 4 is pumped into a sequential adsorption-advanced oxidation reactor. First, it passes through a zeolite adsorption device with a zeolite dosage of 133 g / L and an adsorption speed of 300 r / min for 2 hours to remove residual ammonia nitrogen and other inorganic pollutants. Then, it enters the advanced oxidation device 11, where iron salts and sulfites are added to carry out a Fenton-like oxidation reaction. The concentrations of FeSO4 and Na2SO3 added are both 10 mmol / L, and the reaction is carried out at a speed of 200 r / min for 12 hours to deeply degrade recalcitrant organic matter and separate iron sludge from wastewater. The effluent is pumped into the second intermediate water tank through the second effluent valve 15 and the second effluent gear pump 16. S3. Membrane distillation desalination and concentration: The effluent from the second intermediate water tank 12 is heated to 70°C by the heater 17 and then sent to the membrane distillation reactor 18. Driven by the vapor pressure difference across the membrane, water vapor passes through the membrane pores, and the produced distilled water is pumped into the condenser 19 through the third outlet valve 23 and the third outlet gear pump 24. After being condensed to 20°C, it is collected in the collection tank 20 as high-quality product water and circulated on the outlet side through the circulation pipeline. The hot-side concentrate is returned to the second intermediate water tank 12 through the concentrate circulation pipeline to realize the circulation on the inlet side.

[0042] Example 2 This embodiment follows the same steps as in Embodiment 1, except that the volume ratio of landfill leachate to shale gas wastewater is changed to 18:2.

[0043] Example 3 This embodiment follows the same steps as in Embodiment 1, except that the volume ratio of landfill leachate to shale gas wastewater is changed to 17:3.

[0044] Example 4 This embodiment follows the same steps as in Embodiment 1, except that the volume ratio of landfill leachate to shale gas wastewater is changed to 16:4.

[0045] Example 5 This embodiment follows the same steps as in Embodiment 1, except that the volume ratio of landfill leachate to shale gas wastewater is changed to 15:5.

[0046] Comparative Example 1 This comparative example directly uses the membrane distillation reactor 18 in the above-mentioned treatment system to treat landfill leachate, and the specific treatment steps are the same as step S3 in Example 1.

[0047] Comparative Example 2 This comparative example directly uses the membrane distillation reactor 18 in the above-mentioned treatment system to treat shale gas wastewater. The specific treatment steps are the same as step S3 in Example 1.

[0048] Comparative Example 3 This comparative example uses only the premixing reactor 3 and membrane distillation reactor 18 in the above-mentioned treatment system to treat the mixed wastewater of landfill leachate and shale gas wastewater. The mixing volume ratio of landfill leachate and shale gas wastewater is modified to 17:3. The specific treatment steps are the same as steps S1 and S3 in Example 1. The landfill leachate and shale gas wastewater after premixing treatment are directly fed into membrane distillation reactor 18.

[0049] The permeate water quality and membrane flux in Examples 1-5 and Comparative Examples 1-3 were tested, and the results are as follows: Figure 2 As shown, the membrane flux stability of the system and method protected by this invention is significantly enhanced, and the quality of the produced water is significantly improved.

[0050] The wastewater after premixing treatment in Examples 1-5 contains COD and NH4. + -N and Ca 2+ Mg 2+ The maximum decrease in the concentration of scaling ions was greater than 10%, with Ba 2+ The reduction value can reach up to 39%, and the overall water quality is effectively purified. In contrast, in Comparative Examples 1-2, direct membrane distillation treatment, with a water recovery rate of 75%, resulted in a membrane distillation flux that was 21% lower than that for landfill leachate treatment. However, after the mixed treatment step in stage S1 of Examples 1-5, the membrane distillation flux increased by 36% to 90% compared to the case of treating landfill leachate alone, while the membrane distillation permeability decreased by 17% to 31%, demonstrating a good synergistic effect of treating waste with waste.

[0051] Example 3: After premixing and deep purification treatment, 88% of the NH4+ in the wastewater... + -N, 95% of turbidity and 45% of COD were effectively removed. The membrane distillation flux increased by 6% compared with the mixed wastewater of the same mixing ratio in Comparative Example 3, and the permeate conductivity decreased by 62%, further improving the membrane distillation efficiency.

[0052] Compared to Comparative Example 1, which uses a single membrane distillation process to treat landfill leachate, Comparative Example 3, which treats wastewater pre-mixed with landfill leachate and shale gas wastewater, can increase membrane distillation flux by up to 90% with a 75% water recovery rate, while reducing membrane distillation permeate conductivity by 22%.

[0053] In Example 3, the deep purification treatment under the same mixing ratio conditions increased membrane flux by 6% and decreased permeate conductivity by 62% compared to Comparative Example 3. In Example 3, through the synergistic effect of premixing and deep purification, compared to the landfill leachate alone in Comparative Example 1, NH4-N decreased by 91% and COD decreased by 55%, resulting in significantly improved effluent quality. Using premixing and deep purification as a pre-treatment step reduced the risk of membrane clogging in membrane distillation, while simultaneously increasing the maximum contact angle of the membrane to 101.93° and the liquid inlet pressure to 170 kPa, thus reducing membrane wetting. Compared to the direct treatment of landfill leachate by membrane distillation in Comparative Example 1, the integrated premixing-deep purification-membrane distillation process reduced treatment costs by 30%, demonstrating significant economic advantages.

[0054] Therefore, the present invention provides a co-treatment system and method for landfill leachate and shale gas wastewater, which overcomes the limitations of traditional membrane distillation by using waste to treat waste. It effectively improves water quality and significantly enhances treatment performance by leveraging the complementary properties of the wastewater. It effectively controls the risk of membrane fouling, increases the membrane contact angle, and greatly reduces membrane wetting. The system design combines the dual benefits of freshwater resource utilization and circular economy, providing an efficient and economical solution for the green resource utilization treatment of shale gas wastewater and landfill leachate.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A co-treatment system for landfill leachate and shale gas wastewater, characterized in that: The system includes a premixing unit, a deep purification unit, and a membrane distillation unit connected sequentially via pipelines. The premixing unit includes a first raw water tank, a second raw water tank, a premixing reactor, and a first intermediate water tank. The deep purification unit includes a sequential adsorption-advanced oxidation reactor and a second intermediate water tank. The membrane distillation unit includes a heater, a membrane distillation reactor, a condenser, and a collection tank. The first intermediate water tank is connected to the sequential adsorption-advanced oxidation reactor, and the second intermediate water tank is connected to the heater.

2. The co-treatment system for landfill leachate and shale gas wastewater according to claim 1, characterized in that: The outlets of the first raw water tank and the second raw water tank are respectively connected to the inlet of the premixing reactor through the first inlet gear pump and the second inlet gear pump; an automatic flow regulating component is provided between the first raw water tank and the first inlet gear pump, and between the second raw water tank and the second inlet gear pump; The automatic flow regulation component includes an online flow meter, an inlet valve, and a controller.

3. The co-treatment system for landfill leachate and shale gas wastewater according to claim 2, characterized in that: The outlet of the premixing reactor is connected to the first intermediate water tank in sequence through a first outlet valve and a first outlet gear pump. A stirring assembly is installed inside the premixing reactor.

4. The co-treatment system for landfill leachate and shale gas wastewater according to claim 3, characterized in that: A first inlet valve and a third inlet gear pump are sequentially arranged between the first intermediate water tank and the sequential adsorption-advanced oxidation reactor; a second outlet valve and a second outlet gear pump are sequentially arranged between the sequential adsorption-advanced oxidation reactor and the second intermediate water tank.

5. The co-treatment system for landfill leachate and shale gas wastewater according to claim 4, characterized in that: The sequential adsorption-advanced oxidation reactor includes an adsorption unit and an advanced oxidation unit connected in series. The adsorption unit is filled with zeolite, and the advanced oxidation unit is equipped with a dosing assembly for adding iron salts and sulfites.

6. The co-treatment system for landfill leachate and shale gas wastewater according to claim 5, characterized in that: The outlet of the second intermediate water tank is connected to the heater in sequence through the second inlet valve and the fourth inlet gear pump. The outlet of the heater is connected to the hot side inlet of the membrane distillation reactor. The hot side concentrate outlet of the membrane distillation reactor is returned to the second intermediate water tank through the concentrate circulation pipeline. The cold side outlet of the membrane distillation reactor is connected to the collection tank in sequence through the third outlet valve, the third outlet gear pump, and the condenser.

7. A treatment method based on the co-treatment system for landfill leachate and shale gas wastewater according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Co-mixing: Landfill leachate from the first raw water tank and shale gas wastewater from the second raw water tank are transported to the premixing reactor at a predetermined volume ratio. During this process, two automatic flow control components are used to precisely control the mixing ratio. After the two types of wastewater enter the premixing reactor, they are fully mixed and reacted under stirring conditions. The interaction between organic components and inorganic ions in the two phases of wastewater is used to generate low-pollution intermediate products and flocculants. After the reaction, the mixture is allowed to stand to achieve solid-liquid separation, and the supernatant enters the first intermediate water tank. S2. Deep purification: The supernatant in the first intermediate water tank is pumped into a sequential adsorption-advanced oxidation reactor. First, the residual ammonia nitrogen and other inorganic pollutants are removed by the adsorption device. Then, it enters the advanced oxidation device, where iron salts and sulfites are added to carry out a Fenton-like oxidation reaction to deeply degrade the recalcitrant organic matter. The effluent enters the second intermediate water tank. S3. Membrane distillation desalination and concentration: The effluent from the second intermediate water tank is heated to 60~80℃ by a heater and then sent to the hot side of the membrane distillation reactor. Driven by the vapor pressure difference on both sides of the membrane, water vapor passes through the membrane pores, and the distilled water enters the condenser and is condensed into high-quality product water, which is collected in the product water collection unit. The hot side concentrate is returned to the second intermediate water tank through the concentrate circulation pipeline.

8. The processing method according to claim 7, characterized in that: In S1, the volume ratio of landfill leachate to shale gas wastewater is (15~19):(1~5).

9. The processing method according to claim 7, characterized in that: In S2, the zeolite dosage in the adsorption device is 100~150g / L, and the iron salt and sulfite dosage in the advanced oxidation device are both 8~12mmol / L.

10. The processing method according to claim 7, characterized in that: In S3, the membrane distillation reactor uses a hydrophobic microporous membrane, which is made of one of the following materials: polyvinylidene fluoride, polytetrafluoroethylene, polypropylene, modified polysulfone, modified polyethersulfone, or cellulose ester membrane.

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