Fracturing flow-back fluid concentrated solution and landfill leachate dual-wastewater cooperative treatment method

Abstract

The invention relates to the field of wastewater treatment, and particularly discloses a fracturing flow-back fluid concentrated solution and landfill leachate dual-wastewater cooperative treatment method which comprises the following steps: S1, treating a fracturing flow-back fluid concentrated solution through a BDD oxidation reactor to obtain a pretreatment solution; s2, uniformly mixing the pretreatment liquid with the landfill leachate, and carrying out pH / ORP online adjustment to obtain a reaction liquid; s3, the reaction liquid is subjected to two-stage A / O + MBR biochemical treatment, and a finished product treatment liquid is obtained; the device has the advantages that the double wastewater of the fracturing flow-back fluid concentrated solution and the landfill leachate is subjected to cooperative treatment, and pollutants in the double wastewater are efficiently removed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wastewater treatment, more particularly, it relates to a method for co-treating fracturing flowback fluid concentrate and landfill leachate. BACKGROUND

[0002] The fracturing flowback fluid concentrate is a high-salt, high-pollutant residual liquid produced during the deep treatment of fracturing flowback fluid in the process of oil and gas field development; the landfill leachate is high-concentration organic wastewater produced due to precipitation leaching, water contained in the garbage itself, and decomposition of organic matter in the process of landfill, stacking or incineration of domestic garbage.

[0003] The fracturing flowback fluid concentrate contains high-salt, high-concentration organic matter, heavy metals and other substances, and the landfill leachate contains high-ammonia nitrogen, high-concentration organic matter, heavy metals and other substances. Treating the wastewater of the concentrate and the leachate can not only prevent environmental pollution, but also realize resource recycling.

[0004] In the prior art, the wastewater treatment of the concentrate and the leachate is high in cost, the energy consumption of BDD total oxidation of the fracturing flowback fluid concentrate is high, and the simple biochemical treatment of the landfill leachate is difficult to meet the standard. If the two groups of wastewater are mixed and treated, water quality fluctuation is prone to occur, leading to imbalance of carbon-nitrogen ratio and affecting the biochemical system. Moreover, the mixed treatment of the two groups of wastewater also has the problems of difficulty in electrochemical oxidation and biochemical synergy, inability to accurately treat pollutants, waste of energy consumption due to over-oxidation, and influence on biochemical treatment efficiency due to insufficient oxidation, thereby leading to difficulty in controlling the treatment process.

[0005] Therefore, how to co-treat the fracturing flowback fluid concentrate and the landfill leachate, and efficiently remove the pollutants in the wastewater is a problem to be solved. SUMMARY

[0006] In order to co-treat the fracturing flowback fluid concentrate and the landfill leachate, and efficiently remove the pollutants in the wastewater, the present application provides a method for co-treating fracturing flowback fluid concentrate and landfill leachate.

[0007] The present application provides a method for co-treating fracturing flowback fluid concentrate and landfill leachate, which adopts the following technical scheme: A method for co-treating fracturing flowback fluid concentrate and landfill leachate, comprising the following steps: S1, treating the fracturing flowback fluid concentrate in a BDD oxidation reactor to obtain a pretreated liquid; S2, uniformly mixing the pretreated liquid with the landfill leachate, and adjusting the pH / ORP online to obtain a reaction liquid; S3, treating the reaction liquid by two-stage A / O+MBR biochemical treatment to obtain a finished product treatment liquid.

[0008] By adopting the above technical scheme, the BDD moderately oxidizes the fracturing flowback fluid concentrate, the BDD effluent is used to pre-oxidize the landfill leachate, the biodegradability of the landfill leachate is improved, and then the two-stage A / O+MBR biochemical treatment is used to achieve efficient and low-cost treatment effect.

[0009] During the treatment process of the BDD oxidation reactor, the BDD electrode has extremely high oxygen evolution overpotential and strong oxidation ability, can generate a large amount of hydroxyl radicals, can oxidize and break the polyacrylamide, surfactant, polycyclic aromatic hydrocarbon and other refractory organic matters in the fracturing flowback fluid, and convert them into small molecular organic acids or even mineralize them into carbon dioxide and water, so that the COD in the fracturing flowback fluid is efficiently removed, and the BDD oxidation can break the macromolecular organic matter into easily degradable substances such as acetic acid and propionic acid, and improve the biodegradability, which is convenient for subsequent co-treatment of the two wastewaters.

[0010] The landfill leachate is rich in humic acid, fulvic acid and other macromolecular organic matters, the ORP feedback precisely controls the oxidant dosage, which is convenient for the microbial treatment of wastewater, and in the two-stage A / O (anaerobic-aerobic) system, the anaerobic stage promotes hydrolysis acidification to decompose the macromolecular organic matter into easily degradable small molecular substances, and the aerobic stage fully degrades the biodegradable organic matter through high active sludge concentration, the ultrafiltration membrane in the MBR can intercept the suspended solids and microorganisms to realize efficient solid-liquid separation, further reduce the COD of the effluent, further improve the COD removal rate of the two wastewaters, and the two-stage A / O enhances the nitrification and denitrification capacity, the first-stage anoxic stage uses the carbon source in the influent for denitrification, the second-stage aerobic stage completes the nitrification of ammonia nitrogen, and then realizes deep denitrification through internal reflux to the subsequent anoxic stage to improve the total nitrogen removal efficiency, and the co-treatment of the fracturing flowback fluid concentrate and the landfill leachate is completed, and the pollutants in the two wastewaters are further efficiently removed.

[0011] Preferably, during the treatment process of the BDD oxidation reactor, the COD of the BDD effluent is controlled to be 10000-20000 mg / L, and the ORP is 400-600 mV.

[0012] By adopting the above technical scheme, the COD is controlled to be 10000-20000 mg / L, the preliminary cracking of the refractory organic matter is realized, and the energy waste caused by excessive oxidation is avoided, and the treatment effect of the pollutants is ensured; the ORP is stabilized in the weak oxidation environment of 400-600 mV, the BDD electrode can continuously generate active radicals for attack, if the ORP is too low, it means that the oxidation ability is insufficient, and if the ORP is too high, it means that the water decomposition side reaction zone (oxygen production) has been entered, and the energy utilization rate is reduced, and the 400-600 mV is helpful to maintain high current efficiency, realize the maximum conversion of electric energy to oxidation energy, and ensure the subsequent sewage treatment effect.

[0013] Preferably, in the pH / ORP online regulation process, COD / total nitrogen is controlled at 3-5, and BOD5 / COD ratio is controlled at 0.3-0.5.

[0014] By adopting the technical scheme, COD / total nitrogen is controlled at 3-5, the wastewater contains sufficient available organic matter, full denitrification can be supported, incomplete denitrification caused by insufficient carbon source is avoided, and the bacterial flora balance of the activated sludge system is maintained, and the treatment stability is improved; when BOD5 / COD is controlled in the range of 0.3-0.5, it means that most of the organic matter in the wastewater can be effectively utilized by microorganisms, and is not completely degraded, and sufficient biochemical reaction potential is reserved; if BOD5 / COD is close to 0.6 or more, it means that the organic matter is easily degradable, and does not need to be pretreated deeply; and if BOD5 / COD is less than 0.3, it means that the proportion of the refractory substance is high, and the pretreatment method such as advanced oxidation needs to be strengthened.

[0015] Preferably, in the two-stage A / O+MBR biochemical treatment process, the sludge concentration is 8000-12000 mg / L, and the reflux ratio is 400-600%.

[0016] By adopting the technical scheme, the sludge concentration is limited, the number of microorganisms is ensured, the enrichment and growth of the slowly-increasing nitrifying bacteria, denitrifying bacteria and refractory organic matter degrading bacteria are promoted, and the removal efficiency of COD, ammonia nitrogen and refractory organic matter is improved; if COD or ammonia nitrogen suddenly increases, the high sludge concentration can provide greater buffer capacity, avoid the collapse of the microbial system, and ensure that the effluent meets the standard; and the high concentration of microorganisms can accelerate the wastewater treatment and improve the treatment efficiency; the high reflux ratio of 400-600% can reflux a large amount of nitrated liquid from the aerobic tank to the anoxic tank, provide sufficient nitrate nitrogen, ensure that the two-stage denitrification is fully carried out, significantly improve the total nitrogen (TN) removal rate, and help to fully utilize the biodegradable organic matter in the raw water as an internal carbon source, reduce the demand for external carbon source, and control the reflux ratio to gradually dilute the dissolved oxygen in the reflux liquid, avoid destroying the anaerobic environment of the anoxic zone, ensure the activity of the denitrifying bacteria, and further improve the removal rates of COD and total nitrogen.

[0017] Preferably, the BDD electrode used in the BDD oxidation reactor treatment process is a modified BDD electrode.

[0018] By adopting the technical scheme, the BDD electrode can efficiently generate hydroxyl radicals on the surface under the condition of power supply, can non-selectively oxidize organic pollutants, and is suitable for harsh environments such as strong acid, strong alkali, high salt and high temperature; the BDD electrode is modified to increase the organic matter adsorption sites and hydroxyl radical generation sites on the surface, improve the degradation rate of the pollutants, and prolong the service life of the electrode.

[0019] Preferably, the modified BDD electrode is prepared by treating the surface of the BDD electrode with nickel, depositing gold nanoparticles on the surface of the BDD electrode by magnetron sputtering, and then heat treating and cooling to room temperature.

[0020] By adopting the above technical solution, the surface of the BDD electrode is treated with nickel, which can selectively etch the surface of the BDD electrode to form a uniform distribution of nano-sized hole structures on the electrode surface, thereby increasing the effective reaction area of the electrode. In combination with the subsequent magnetron sputtering deposition of gold nanoparticles, the gold nanoparticles can form a composite connection network with the nickel etching, thereby increasing the effective reaction area and mass transfer efficiency of the electrode, further improving the contact area between the pollutants and the electrode, and also improving the utilization rate of hydroxyl radicals, thereby significantly improving the degradation rate of pollutants. Moreover, the gold nanoparticles have excellent electro-oxidation catalytic ability for various phenolic and amine organic substances, can reduce the reaction activation energy, and accelerate the degradation of pollutants. Gold ions can also improve the electron transfer performance of the electrode and increase the current efficiency. In the process of treating double waste water with complex components, the pollutants can be efficiently and quickly treated, and the interference of side reactions is reduced. Finally, the heat treatment can increase the sphericity of the gold nanoparticles and make them uniformly distributed and embedded in the nickel etched holes to form an inlaid structure, thereby effectively preventing the loss of nano-ions due to wastewater erosion during long-term use, and prolonging the service life of the BDD electrode.

[0021] Preferably, the BDD electrode is treated with nickel, and the specific steps are as follows: The surface of the BDD electrode is magnetron sputtered with a pure nickel target to form a nickel film, and then the temperature is raised to 800-920℃ for 2-4h.

[0022] By adopting the above technical solution, a uniform nickel film is deposited on the surface of the BDD electrode by magnetron sputtering technology. Nickel has high carbon solubility and catalytic activity, which can promote the reconstruction and etching of carbon atoms on the surface of diamond during subsequent high-temperature treatment, forming a micro-nano-sized pit structure on the surface of the BDD electrode. The porous structure significantly increases the specific surface area of the BDD electrode, increases the opportunity to contact pollutants, and exposes more electrochemically active edge sites, which is beneficial to the generation and mass transfer and diffusion of hydroxyl radicals, and can more efficiently treat organic matter and ammonia nitrogen in fracturing flowback fluid concentrate.

[0023] Preferably, the magnetron sputtering power for depositing gold nanoparticles is 80-100W, and the time is 60-90s.

[0024] By adopting the above technical solution, the power and time are limited to promote the uniform nucleation of gold on the porous BDD surface etched by nickel. The microporous structure produced by nickel etching provides physical anchoring points for gold nanoparticles, preventing them from falling off in high-salt and high-organic load environments, significantly improving the long-term stability of the electrode, and also increasing the specific surface area and improving the treatment efficiency of the BDD electrode.

[0025] Preferably, the temperature of the heat treatment is 400-600 DEG C.

[0026] By adopting the technical scheme, the deposited gold atoms diffuse, agglomerate and spheroidize to form nanoparticles with uniform size, and are firmly 'pinned' in the hole structure formed by nickel etching, thereby significantly improving the long-term stability of the electrode.

[0027] Preferably, the average particle size of the gold nanoparticles is 15-35 nm.

[0028] By adopting the technical scheme, the gold nanoparticles can be uniformly distributed in the micro-nano pits etched by nickel, thereby increasing the specific surface area of the BDD electrode and prolonging the service life.

[0029] In summary, the present application has the following beneficial effects: 1. The BDD moderately oxidizes the fracturing flowback fluid concentrate, the oxidation of the BDD effluent is used to pre-oxidize the landfill leachate, the biodegradability of the landfill leachate is improved, and the two-stage A / O+MBR biochemical treatment is used to realize the high-efficiency and low-cost treatment effect.

[0030] 2. The surface of the BDD electrode is treated with nickel, the nickel can selectively etch the surface of the BDD electrode to form a uniform nanoscale hole structure on the surface of the electrode, increase the effective reaction area of the electrode, and cooperate with the subsequent magnetron sputtering deposition of gold nanoparticles, the gold nanoparticles can form a composite connection network with the nickel etching, increase the effective reaction area and mass transfer efficiency of the electrode, thereby further increasing the contact area of the pollutants and the electrode, and also improving the utilization rate of hydroxyl radicals, and greatly improving the degradation rate of the pollutants.

[0031] 3. The gold nanoparticles have excellent electro-oxidation catalytic ability for various phenolic and amine organic matters, can reduce the reaction activation energy and accelerate the degradation of the pollutants, the gold ions can also improve the electron transfer performance of the electrode and increase the current efficiency, in the treatment process of the complex component double waste water, the pollutants can be efficiently and quickly treated, and the interference of the side reaction is reduced; finally, the heat treatment can promote the increase of the sphericity of the gold nanoparticles and the uniform distribution of the gold nanoparticles, the gold nanoparticles are embedded in the holes etched by nickel to form an inlaid structure, the loss of the nanometer ions due to the washing of the waste water is effectively prevented, and the service life of the BDD electrode is prolonged.

[0032] 4. The thickness of the magnetron sputtered nickel film is limited to cooperate with the particle size of the magnetron sputtered gold nanoparticles, the embedding effect is ensured, the specific surface area is increased, the modified BDD electrode has a large specific surface area to contact the pollutants, and also has a long service life. DETAILED DESCRIPTION

[0033] The present application is further described below in conjunction with embodiments.

[0034] All of the following ingredients are commercially available.

[0035] Example of preparation of modified BDD electrode

[0036] Preparation Example 1: The modified BDD electrode was prepared using the following method: A pure nickel target with a purity of 99.99% was magnetron sputtered onto the surface of a commercially available BDD electrode. The sputtering power was 80W, and the argon bombardment was 0.5Pa, forming a nickel film with an average thickness of 30nm. The film was then heated to 860℃ for 3 hours to complete the nickel treatment. After that, a pure gold target with a gold purity of 99.99% was magnetron sputtered at a power of 90W for 80 seconds, resulting in gold nanoparticles with an average particle size of 25nm. The film was then heat-treated at 500℃ for 1 hour and cooled to room temperature to obtain the finished modified BDD electrode.

[0037] Preparation Example 2: The difference between this preparation example and Preparation Example 1 is that: A pure nickel target with a purity of 99.99% was magnetron sputtered onto the surface of the BDD electrode. The sputtering power was 80W, and the argon bombardment was 0.5Pa, forming a nickel film with an average thickness of 30nm. The film was then heated to 800℃ for 4h to complete the nickel treatment. After that, a pure gold target with a gold purity of 99.99% was magnetron sputtered. The sputtering power was 80W, and the time was 90s, resulting in gold nanoparticles with an average particle size of 15nm. The film was then heat-treated at 400℃ for 1.5h and cooled to room temperature to obtain the finished modified BDD electrode.

[0038] Preparation Example 3: The difference between this preparation example and Preparation Example 1 is that: A pure nickel target with a purity of 99.99% was magnetron sputtered onto the surface of the BDD electrode. The sputtering power was 80W, and the argon bombardment was 0.5Pa, forming a nickel film with an average thickness of 30nm. The film was then heated to 920℃ for 2h to complete the nickel treatment. After that, a pure gold target with a gold purity of 99.99% was magnetron sputtered. The sputtering power was 100W, and the time was 60s, resulting in gold nanoparticles with an average particle size of 35nm. The film was then heat-treated at 600℃ for 0.5h and cooled to room temperature to obtain the finished modified BDD electrode. Example

[0039] Example 1: A method for synergistic treatment of fracturing flowback fluid concentrate and landfill leachate as dual wastewaters: S1. The fracturing flowback concentrate is treated by a BDD oxidation reactor. The BDD electrode used is commercially available. The COD of the BDD effluent is controlled at 15000 mg / L and the ORP is stable at 500 mV. The BOD / COD ratio is ensured to rise to above 0.3 to obtain the pretreated solution. S2. The pretreated liquid and landfill leachate are mixed evenly and adjusted online in the equalization tank using pH / ORP. A flow regulating valve is installed on the mixing pipeline of BDD oxidation effluent and landfill leachate raw water. The mixing ratio is dynamically adjusted according to the online monitoring of "BDD effluent COD concentration" and "landfill leachate NH3-N concentration" to maintain COD / total nitrogen at 4 and BOD5 / COD ratio at 0.4, thus obtaining the reaction solution. S3. The reaction solution undergoes two-stage A / O+MBR biochemical treatment, with a sludge concentration of 10000 mg / L and a reflux ratio of 500%, to obtain the finished treated solution.

[0040] Example 2: The difference between this example and Example 1 is that: S1. The fracturing flowback concentrate is treated by a BDD oxidation reactor. The BDD electrode used is the modified BDD electrode prepared in Preparation Example 1. The COD of the BDD effluent is controlled at 15000 mg / L and the ORP is stable at 500 mV. The BOD / COD ratio is increased to above 0.3 to obtain the pretreated solution. S2. The pretreated liquid and landfill leachate are mixed evenly and adjusted online in the equalization tank using pH / ORP. A flow regulating valve is installed on the mixing pipeline of BDD oxidation effluent and landfill leachate raw water. The mixing ratio is dynamically adjusted according to the online monitoring of "BDD effluent COD concentration" and "landfill leachate NH3-N concentration" to maintain COD / total nitrogen at 4 and BOD5 / COD ratio at 0.4, thus obtaining the reaction solution. S3. The reaction solution undergoes two-stage A / O+MBR biochemical treatment, with a sludge concentration of 10000 mg / L and a reflux ratio of 500%, to obtain the finished treated solution.

[0041] Example 3: The difference between this example and Example 2 is that: S1. The fracturing flowback concentrate is treated in a BDD oxidation reactor. The BDD electrode used is the modified BDD electrode prepared in Preparation Example 2. The COD of the BDD effluent is controlled at 10000 mg / L and the ORP is stable at 400 mV. The BOD / COD ratio is increased to above 0.3 to obtain the pretreated solution. S2. The pretreated liquid and landfill leachate are mixed evenly and adjusted online in the equalization tank using pH / ORP. A flow regulating valve is installed on the mixing pipeline of BDD oxidation effluent and landfill leachate raw water. The mixing ratio is dynamically adjusted according to the online monitoring of "BDD effluent COD concentration" and "landfill leachate NH3-N concentration" to maintain COD / total nitrogen at 3 and BOD5 / COD ratio at 0.3, thus obtaining the reaction solution. S3. The reaction solution undergoes two-stage A / O+MBR biochemical treatment, with a sludge concentration of 8000 mg / L and a reflux ratio of 400%, to obtain the finished treated solution.

[0042] Example 4: The difference between this example and Example 2 is that: S1. The fracturing flowback concentrate is treated in a BDD oxidation reactor. The BDD electrode used is the modified BDD electrode prepared in Preparation Example 3. The COD of the BDD effluent is controlled at 20000 mg / L and the ORP is stable at 600 mV. The BOD / COD ratio is increased to above 0.3 to obtain the pretreated solution. S2. The pretreated liquid and landfill leachate are mixed evenly and adjusted online in the equalization tank using pH / ORP. A flow regulating valve is installed on the mixing pipeline of BDD oxidation effluent and landfill leachate raw water. The mixing ratio is dynamically adjusted according to the online monitoring of "BDD effluent COD concentration" and "landfill leachate NH3-N concentration" to maintain COD / total nitrogen at 5 and BOD5 / COD ratio at 0.5, thus obtaining the reaction solution. S3. The reaction solution undergoes two-stage A / O+MBR biochemical treatment, with a sludge concentration of 12000 mg / L and a reflux ratio of 600%, to obtain the finished treated solution.

[0043] Example 5: The difference between this example and Example 2 is that: During the preparation of the modified BDD electrode, nickel was not sputtered by magnetron sputtering, nor was there any heating treatment.

[0044] Example 6: The difference between this example and Example 2 is that: During the preparation of the modified BDD electrode, no gold nanoparticles were magnetron sputtered, and no heat treatment was performed.

[0045] Performance testing 1. Pollutant removal rate

[0046] Wastewater was treated using the methods described in Examples 1-6. After continuous operation for 72 hours, the removal rates of COD and total nitrogen were calculated. The removal rate was calculated as (influent - effluent) / influent × 100%, where influent represents the COD or total nitrogen concentration at the influent point and effluent represents the COD or total nitrogen concentration at the effluent point. The data were recorded.

[0047] Table 1 Performance Test Table

[0048] As can be seen from Example 1 and Table 1, the dual wastewater synergistic treatment method of this application can not only improve the removal rate of pollutants in wastewater, but also maintain a high removal rate after long-term use.

[0049] As can be seen from Examples 1 and 2-4 and Table 1, the modified BDD electrode has a large specific surface area and is not easily affected by sewage during long-term use. It can efficiently remove pollutants from wastewater, promote subsequent biochemical treatment, improve treatment efficiency, and extend service life.

[0050] Combining Examples 2 and 5-6 with Table 1, it can be seen that in the preparation process of the modified BDD electrode in Example 5, no nickel was magnetron sputtered and no temperature treatment was performed. Compared with Example 2, the COD removal rate and total nitrogen removal rate of Example 5 were lower than those of Example 2. This indicates that the nickel film magnetron sputtered on the surface of the BDD electrode has high carbon solubility and catalytic activity. In the subsequent high-temperature treatment, it can promote the reconstruction and etching of carbon atoms on the diamond surface, forming a micro-nano-scale pit structure on the surface of the BDD electrode. The porous structure significantly increases the specific surface area of ​​the BDD electrode, increases the opportunity for contact with contaminants, and exposes more electrochemically active edge sites, which is conducive to the generation and mass transfer diffusion of hydroxyl radicals. It can more efficiently treat organic matter, ammonia nitrogen and other substances in the fracturing flowback concentrate.

[0051] In the preparation of the modified BDD electrode in Example 6, no gold nanoparticles were magnetron sputtered and no heat treatment was performed. Compared with Example 2, the COD removal rate and total nitrogen removal rate of Example 6 were lower than those of Example 2. This indicates that gold is uniformly nucleated on the porous BDD surface formed by nickel etching. The microporous structure generated by nickel etching provides physical anchoring points for gold nanoparticles, preventing them from falling off in high-salt and high-organic-load environments, significantly improving the long-term stability of the electrode, and also increasing the specific surface area and improving the processing efficiency of the BDD electrode.

[0052] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for the synergistic treatment of fracturing flowback fluid concentrate and landfill leachate as dual wastewaters, characterized in that, Includes the following steps: S1. The concentrated fracturing flowback fluid is treated in a BDD oxidation reactor to obtain a pretreated solution; S2. The pretreatment liquid and landfill leachate are mixed evenly and adjusted online by pH / ORP to obtain the reaction solution; S3. The reaction solution undergoes two-stage A / O+MBR biochemical treatment to obtain the finished treatment solution.

2. The method for synergistic treatment of fracturing flowback fluid concentrate and landfill leachate as described in claim 1, characterized in that: During the treatment process in the BDD oxidation reactor, the COD of the BDD effluent is controlled at 10,000-20,000 mg / L, and the ORP is at 400-600 mV.

3. The method for synergistic treatment of fracturing flowback fluid concentrate and landfill leachate as described in claim 1, characterized in that, During the online pH / ORP adjustment process, the COD / total nitrogen ratio is controlled at 3-5, and the BOD5 / COD ratio is controlled at 0.3-0.

5.

4. The method for synergistic treatment of fracturing flowback fluid concentrate and landfill leachate as described in claim 1, characterized in that, In the two-stage A / O+MBR biological treatment process, the sludge concentration is 8000-12000 mg / L, and the reflux ratio is 400-600%.

5. The method for synergistic treatment of fracturing flowback fluid concentrate and landfill leachate as described in claim 1, characterized in that, The BDD electrode used in the BDD oxidation reactor process is a modified BDD electrode.

6. The method for synergistic treatment of fracturing flowback fluid concentrate and landfill leachate as described in claim 5, characterized in that, The modified BDD electrode is prepared by treating the surface of a BDD electrode with nickel, depositing gold nanoparticles by magnetron sputtering, followed by heat treatment and cooling to room temperature.

7. The method for synergistic treatment of fracturing flowback fluid concentrate and landfill leachate as described in claim 6, characterized in that, The BDD electrode is nickel-treated, and the specific steps are as follows: Pure nickel target material is magnetron sputtered onto the surface of the BDD electrode to form a nickel film, and then the film is treated at 800-920℃ for 2-4 hours.

8. The method for synergistic treatment of fracturing flowback fluid concentrate and landfill leachate as described in claim 6, characterized in that, The magnetron sputtering power for depositing gold nanoparticles is 80-100W, and the time is 60-90s.

9. The method for synergistic treatment of fracturing flowback fluid concentrate and landfill leachate as described in claim 6, characterized in that, The heat treatment temperature is 400-600℃.

10. The method for synergistic treatment of fracturing flowback fluid concentrate and landfill leachate as described in claim 6, characterized in that, The average particle size of the gold nanoparticles is 15-35 nm.

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