Fe / C load-based membrane module, PN / A-MABR autotrophic nitrogen removal device, preparation method and sewage treatment method

Abstract

The invention discloses a Fe / C loaded membrane module, a PN / A-MABR autotrophic nitrogen removal device, a preparation method and a sewage treatment method, and belongs to the technical field of sewage treatment. According to the invention, the problem that the treatment effect is influenced by NO3 <->-N accumulation in the existing membrane aeration coupling partial nitrification-anaerobic ammonia oxidation process is solved. Comprising a frame and a membrane body attached to the outer portion of the frame, the membrane body comprises a hydrophobic organic membrane layer, an iron-carbon material layer and a biological membrane layer which are sequentially arranged, and the hydrophobic organic membrane layer is attached to the outer portion of the frame. The iron-carbon material is added between the hydrophobic organic membrane layer and the biological membrane layer, the iron-carbon micro-electrolysis process is coupled with the dissimilatory process of nitrate generated by microbial metabolism, the removal of NO3 <->-N generated by anaerobic ammonia oxidation is enhanced, and the total nitrogen removal efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a Fe / C load-based membrane assembly, a PN / A-MABR autotrophic denitrification device, a preparation method and a sewage treatment method, belonging to the technical field of sewage treatment. BACKGROUND

[0002] The emerging partial nitrification / anaerobic ammonia oxidation (PN / A) process can be coupled with a membrane aeration biofilm reactor (MABR) to oxidize part of NH4 + -N to NO2 - -N for subsequent anaerobic ammonia oxidation reaction, greatly reducing the aeration amount and energy consumption, saving costs without the need for external organic carbon source. In addition, the PN / A technology can reduce the emission of greenhouse gases (such as N2O) under certain conditions, which is more conducive to achieving the goal of low carbon emission in the sewage treatment process and meets the requirements of sustainable development. Even if the coupling of PN / A technology and MABR reactor can greatly reduce the required aeration amount, if the oxygen supply to the reactor body cannot be strictly controlled, it is easy to cause excessive dissolved oxygen (DO) in the reactor water, leading to the continuous oxidation of NO2 - -N by nitrite oxidizing bacteria (NOB), reducing the substrate concentration of anaerobic ammonia oxidation reaction while increasing the concentration of NO3 - -N, affecting the denitrification efficiency. More critically, even if the nitrification process can be accurately controlled, according to the Anammox metabolic process, about 11% of nitrogen elements will be produced in the form of NO3 - -N and accumulated in the system.

[0003] In the existing MABR-PN / A technology, the mainstream research is mainly about how to inhibit the abundance and activity of NOB in the system, one of the methods is to control the DO concentration in the system. By coupling MABR and PN / A technology, the DO concentration can be effectively controlled, but due to the heterogeneous mass transfer characteristics of MABR, the DO concentration on the inner layer of the biofilm is the highest, and once the oxygen supply is excessive, a large number of NOB will still grow, and the sludge consumption of NOB growing in the inner layer is extremely low, which is difficult to remove, and thus high concentration of NO3 - -N is easily produced and accumulated on the inside of the biofilm, affecting the treatment effect and denitrification efficiency of the subsequent anaerobic ammonia oxidation process, and the anaerobic ammonia oxidation process itself will produce about 11% of NO3 - -N, so improving the conversion rate of NO3 - -N dissimilation can further improve the denitrification efficiency.

[0004] In the prior art, iron-carbon is usually directly added to the equipment to enhance the effect of sewage treatment. Direct addition of iron-carbon can cause a long distance between the iron-carbon material and the biofilm, and the mass transfer resistance between the electrons produced by micro-electrolysis and the target electron acceptor NO3 - -N is large, which is not conducive to the utilization of the micro-electrolysis products by the biofilm. Direct addition of nano-iron powder has a faster iron release rate and stronger iron supply capacity in the short term, but the surface energy and magnetic force can cause aggregation, resulting in reduced reaction activity. High reaction activity can lead to rapid oxidation and consumption of nano-iron powder, which requires frequent addition of materials and shortens the service life.

[0005] Therefore, there is an urgent need for a new MABR membrane assembly and PN / A-MABR autotrophic denitrification device to solve the problem of NO3 - -N accumulation affecting the treatment effect in the existing membrane aeration coupled partial nitrification-anammox process. SUMMARY

[0006] The present application is to solve the problem of NO3 - -N accumulation affecting the treatment effect in the existing membrane aeration coupled partial nitrification-anammox process, and further provides a Fe / C-loaded membrane assembly, a PN / A-MABR autotrophic denitrification device, a preparation method and a sewage treatment method.

[0007] The technical solution adopted by the present application to solve the above technical problems is: A Fe / C-loaded membrane assembly, comprising a frame and a membrane body attached to the outside of the frame, the membrane body comprising a hydrophobic organic membrane layer, an iron-carbon material layer and a biofilm layer arranged in sequence, wherein the hydrophobic organic membrane layer is attached to the outside of the frame.

[0008] Further, the thickness of the iron-carbon material layer is 0.05mm-0.15mm, and the thickness of the hydrophobic organic membrane layer is 0.5mm or less.

[0009] Further, the frame comprises a frame body and an organic glass baffle, wherein the frame body has a rectangular structure, the number of membrane bodies is at least one, the organic glass baffle has a rectangular structure and is fixed to the outside of the frame body without the membrane body, and at least one organic glass baffle is provided with an air inlet.

[0010] A PN / A-MABR autotrophic denitrification device, comprising the above Fe / C-loaded membrane assembly, further comprising a reactor body, a gas cylinder and a magnetic stirrer, wherein the membrane assembly is installed in the reactor body and connected to the gas cylinder through a gas supply pipeline, the magnetic stirrer is arranged at the bottom end of the reactor body, and the reactor body is provided with an inlet / outlet water port.

[0011] Further, the water inlet / outlet is connected with a water inlet tank and a water outlet tank through pipelines.

[0012] Further, the water inlet tank is connected with the water inlet / outlet through a water inlet pipeline, and the water outlet tank is connected with the water inlet / outlet through a water outlet pipeline.

[0013] Further, the top end of the reactor body is an open end, and a top cover is arranged on the open end.

[0014] Further, the gas supply pipeline is provided with a pressure gauge, a flow meter and a gas pipe valve.

[0015] A preparation method of the membrane assembly, comprising the following steps: Step one, straw pretreatment: The straw is soaked in a ferric chloride solution, and the straw and the ferric chloride form a mixture, the ratio of the ferric chloride to the mixture is 45 / 100, and the soaking time is 2 h; Step two, drying treatment: The mixture obtained in step one is dried in an oven at 60℃ for 6 h; Step three, tubular furnace pyrolysis: The mixture dried in step two is pyrolyzed in a tubular furnace under N2 atmosphere at a heating rate of 10℃ / min at 600℃ for 2 h; Step four, preparation of suspension: The mixture pyrolyzed in step three is ultrasonically dispersed in deionized water to obtain a suspension; Step five, vacuum filtration: The iron-carbon material in the suspension obtained in step four is quickly and uniformly deposited on the surface of the hydrophobic organic membrane layer by using the transmembrane pressure difference generated by vacuum to form an active layer with controllable thickness; Step six, reactor assembly: The membrane body containing the iron-carbon material layer and the hydrophobic organic membrane layer obtained in step five is fixed on the frame by adhesion to form a membrane assembly, then the membrane assembly is installed in the reactor body, and at the same time, a gas source is connected, and finally the reactor body is sealed; Step seven, reactor tightness detection; Step eight, reactor biofilm formation: After the reactor tightness detection is qualified, nitrosation sludge and anaerobic ammonia oxidation sludge are added into the reactor body, water is fed into the reactor body, and then the reactor body is operated in an SBR mode at room temperature, the hydraulic retention time is 4-48 h, then gas is supplied into the membrane assembly, the dissolved oxygen concentration in the reactor body is controlled to be below 0.5 mg / L, and after 1-4 weeks, when brownish-brown biofilm is attached to the membrane assembly, it is determined that the reactor is successfully biofilm-formed.

[0016] A sewage treatment method, using the above-mentioned PN / A-MABR autotrophic denitrification device, is operated in an SBR mode, in which, in one operation cycle, raw water is fed into the reactor, a gas cylinder is opened for continuous aeration, the aeration flow rate is maintained below 0.5 mL / min, and the dissolved oxygen concentration in the reactor is maintained below 0.5 mg / L, the speed of the magnetic stirrer is controlled within 200-800 rpm in one operation cycle to achieve complete mixing of the water and sludge in the reactor, and after the operation is completed, the water in the reactor is discharged, and after one operation cycle is completed, the operation of the next cycle is started.

[0017] Compared with the prior art, the present application has the following effects: The iron-carbon material is added between the hydrophobic organic membrane layer and the biofilm layer, the iron-carbon micro-electrolysis process is coupled with the nitrate dissimilation process generated by microbial metabolism, the NO3 - -N removal, and the total nitrogen removal efficiency is improved, one is to increase the contact area between the biofilm and the iron-carbon material, shorten the distance between the electron acceptor and the electron donor, and reduce the mass transfer resistance between the electron and the NO3 - -N, so that the NO3 - -N generated in the inner layer of the biofilm can receive electrons faster, realize in-situ reduction of NO3 - -N; two is that the nano-iron powder is fixed on the surface of the membrane material through the suction filtration process to form a fixed activation layer, which can further reduce the loss of iron after the stable growth of the biofilm, avoid the agglomeration and loss caused by direct addition, and in addition, the iron-carbon material layer obtained by suction filtration can slow down the reaction activity to achieve the goal of slow and continuous release of iron ions; third, the direct contact of the iron-carbon material with the biofilm enables the biofilm to simultaneously and directly utilize oxygen and electrons provided by the iron-carbon, greatly improving the utilization efficiency of electrons, and the Fe 2+ generated by the iron-carbon micro-electrolysis is directly utilized by the biofilm, the expression of the nrfA gene is up-regulated, further promoting the expression of the DNRA process of the biofilm and strengthening the in-situ reduction of NO3 - -N; in addition, the iron-carbon material is compressed between the biofilm and the hydrophobic organic membrane layer, further reducing the volume of the membrane assembly and the volume of the reactor. -

[0018] The Fe 2+ generated by the iron-carbon micro-electrolysis can be directly utilized by the microorganisms, and the in-situ dissimilation of NO3 - -N generated in the inner layer of the biofilm is further realized. 2+ ​The increase of the concentration of the protein can increase the amount of heme in the microorganism, promote the production of cytochrome c and n rfA The expression of the protein not only improves the electron transfer ability of the microorganism, but also enhances the dissimilation ability of the microorganism to NO3 - -N. Compared with the prior art, the effective reduction of NO3 - -N and electrons, Fe 2+ and the mass transfer resistance of the microorganism, realizes the in-situ reduction of NO3 - -N, reduces the accumulation of NO3 - -N in the reactor, further improves the denitrification efficiency of the PN / A technology, and provides a simple and effective treatment strategy for solving the accumulation of NO3 - -N in the system due to the nitrification process and the anaerobic ammonia oxidation process.

[0019] The nitrate dissimilation process is a process of reducing NO3 - -N to NO2 - -N, and further reducing NO2 + -N to NH4 + -N. The process consumes the electrons generated by the iron-carbon micro-electrolysis, but NH4 0 -N will generate electrons for the reduction of iron ions, so the cycle process of Fe 2+ oxidation and Fe 3+ reduction will continue to occur in the reaction process; the formation of cytochrome c promotes the direct transfer of electrons, and although the protein consumes iron elements, the iron elements in cytochrome c only exist as structural cofactors, and the consumption is very small. Moreover, the "consumption" of iron in the system is not lost, but is transformed into an intracellular active iron pool. After the cell death, the iron elements will be released into the system through lysis-recycling, and then participate in the next round of iron cycle. The iron-carbon material is actually recycled in the system, rather than permanently consumed, so the addition of the iron-carbon material only needs to be done once. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a structural composition schematic diagram (explosion schematic diagram) of the Fe / C load-based membrane assembly of the present application; Figure 2 It is a structural schematic diagram of the PN / A-MABR autotrophic denitrification device of the present application.

[0021] In the figure: 1. Biofilm layer; 2. Iron-carbon material layer; 3. Hydrophobic organic membrane layer; 4. Frame; 8. Reactor body; 9. Inlet pump; 10. Outlet pump; 11. Inlet pipe; 12. Outlet pipe; 13. Inlet tank; 14. Outlet tank; 15. Top cover; 16. Flange; 17. Inlet / outlet; 18. Inlet valve; 19. Outlet valve; 20. Gas cylinder; 21. Flow meter; 22. Pressure gauge; 23. Gas supply pipe; 24. Membrane module; 25. Gas pipe valve; 26. Magnetic stirrer. Detailed Implementation

[0022] Specific implementation method one: Combining Figures 1-2 This description of embodiments provides a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the descriptions of "front," "rear," "left," "right," "inner," "outer," "left side," "right side," "upper part," "lower part," "top," and "bottom" in this invention are defined based on the orientation or positional relationships shown in the accompanying drawings. They are merely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the described structure must be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0024] In the description of this invention, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] A Fe / C-loaded membrane module includes a frame 4 and a membrane body attached to the outside of the frame 4. The membrane body comprises a hydrophobic organic membrane layer 3, an iron-carbon material layer 2, and a biofilm layer 1 arranged sequentially, wherein the hydrophobic organic membrane layer 3 is attached to the outside of the frame 4. The frame 4 is thus designed as a rectangular frame. The prepared iron-carbon microelectrolysis powder material is fixed to the surface of the hydrophobic organic membrane by vacuum filtration. The membrane body and the frame 4 can be bonded together using AB glue or other adhesive methods to ensure that the iron-carbon powder layer is located between the membrane material and the biofilm during subsequent reactions, thus facilitating the generation of NO3 during the reaction. --N comes into direct contact with iron-carbon materials, facilitating NO3-- - In-situ utilization and dissimilar reduction of -N. Compared with existing iron-carbon packing methods, iron-carbon microelectrolysis materials are located in areas where NO3 is most easily generated. - The -N inner layer of the biofilm facilitates the biofilm's absorption of electrons and Fe generated by iron-carbon microelectrolysis. 2+ Direct utilization reduces NO3 - Mass transfer resistance between -N dissimilatory and electron transport, avoiding electron acceptor / donor and Fe 2+ It is consumed during transport, increasing the concentration of iron, carbon, and NO3. - -N in-situ utilization rate.

[0026] Iron is a core element of the heme molecule and a key gene in the dissimilatory nitrate reduction (DNRA) process. nrfA Gene-encoded nitrite reductase n rfA It is a heme-dependent enzyme. In the MABR PN / A system, the microelectrolysis reaction of iron-carbon materials (Fe 0 →Fe 2+ It can continuously release soluble ferrous iron, Fe. 2+ It directly participates in the assembly of the porphyrin ring and provides essential raw materials for heme synthesis by activating ferrous chelase to catalyze the final heme formation. Previous studies have shown that the abundance of heme in biological membranes is related to... nrfA The expression levels were positively correlated, and NrfA Enzyme activity is highly dependent on the integrity of the heme cofactor. Furthermore, heme is the active site of cytochrome c, which acts as an electron carrier; insufficient heme concentration may hinder cytochrome c assembly, affecting the integrity of the electron transport chain.

[0027] Addressing the shortcomings of existing technologies in practical applications, this invention adds iron-carbon materials between a hydrophobic organic membrane layer and a biofilm layer 1. The iron-carbon micro-electrolysis process is coupled with the nitrate dissociation process produced by microbial metabolism, synergistically removing pollutants from the water. This increases the contact area between the biofilm and the iron-carbon materials, shortens the distance between the electron acceptor and electron donor, and reduces the interaction between electrons and NO3. - Mass transfer resistance between -N facilitates the formation of NO3 in the inner layer of the biofilm. - -N can accept electrons more quickly, thus achieving NO3- -The process involves two main aspects: first, the in-situ reduction of -N; second, the fixation of nano-iron powder onto the membrane material surface through filtration to form a fixed activation layer, which further reduces iron loss after the biofilm has grown stably, avoiding agglomeration and loss caused by direct addition; third, the iron-carbon material layer 2 obtained by filtration can slow down the reaction activity, achieving the goal of slow and continuous release of iron ions; and fourth, the direct contact between the iron-carbon material and the biofilm allows the biofilm to simultaneously and directly utilize oxygen and electrons provided by iron and carbon, greatly improving the efficiency of electron utilization, and the Fe produced by iron-carbon micro-electrolysis... 2+ It is directly utilized by biological membranes, by increasing heme concentration and upregulating... nrfA Gene expression further promotes the expression of the DNRA process in biomembranes, enhancing the expression of NO3. - In-situ reduction of -N alleviates the NO3- produced in the reaction system due to excessive NOB growth and the Anammox process. - -N accumulation; in addition, compressing the iron-carbon material between the biofilm and the hydrophobic organic membrane layer 3 further reduces the volume of the membrane module 24, thereby reducing the reactor volume.

[0028] Fe produced during iron-carbon micro-electrolysis 2+ It can be directly utilized by microorganisms, and further realize the generation of NO3 from the inner layer of the biofilm. - In-situ dissimilatory transformation of -N. Fe within the system 2+ Increased concentrations of [specific substance] can increase heme production within microorganisms, while simultaneously promoting cytochrome c and n [specific compounds]. rfA Protein expression not only further enhanced the electron transport capacity of microorganisms, but also strengthened their resistance to NO3. - The dissimilatory power of -N. Compared with existing technologies, it effectively reduces NO3. - -N and electrons, Fe 2+ Overcoming mass transfer resistance with microorganisms to achieve NO3 - In-situ reduction of -N reduces NO3 in the reactor. - -N accumulation further improves the nitrogen removal efficiency of PN / A technology, addressing the NO3 generated by nitrification and anaerobic ammonium oxidation processes within the system. - -N accumulation proposes a simple and effective processing strategy.

[0029] The nitrate dissociation process is the process of converting NO3 into nitrogen. - -N is reduced to NO2 - -N is further reduced to NH4. + The -N process consumes electrons generated by the micro-electrolysis of iron and carbon, but in the nitration process, NH4+... + -N electrons are generated, which are then used to reduce iron ions. Therefore, Fe2+ will continue to be generated during the reaction. 0 Oxidation and Fe 2+ / Fe3+ The reduction cycle process; the formation of cytochrome c promotes the direct transfer of electrons, although the protein consumes iron elements, the iron elements in cytochrome c only exist as a structural cofactor, the consumption is very small, and the "consumption" of iron in the system is not lost, but is transformed into an intracellular active iron pool. After cell death, the iron elements will be released into the system again through lysis-recycling, and then participate in the next round of iron cycle. The iron-carbon material is actually recycled in the system, not permanently consumed, so the addition of the iron-carbon material only needs to be done once.

[0030] The membrane aeration mode can greatly improve the utilization rate of oxygen while reducing energy consumption, and at the same time, as much as possible to avoid the NOB occupying the dominant position of the microbial community due to the too high dissolved oxygen concentration in the system, but this change in aeration measure still cannot completely avoid the existence of NOB. Especially in the MABR-PN / A, the inner layer of the biological membrane has the highest dissolved oxygen concentration, which is most likely to cause the massive reproduction of NOB, and is the main place for the production of NO3 - -N, therefore, the iron-carbon powder layer is placed between the membrane material and the biological membrane, reducing the mass transfer resistance between the electron acceptor and the electron donor, and facilitating the direct contact of the NO3 - -N produced by NOB with the iron-carbon material for in-situ reduction; in addition, the lower dissolved oxygen concentration can alleviate the massive oxidation of the iron-carbon material, especially in the reactor where the arrangement of the iron-carbon material is closer to the oxygen source. The present application comprehensively considers the advantages and disadvantages of the two ways of filling and adding nano-iron powder, and uses the powdered iron-carbon material fixed on the surface of the membrane material, so that the iron-carbon material directly contacts the biological membrane in the subsequent biological reaction, reducing the mass transfer resistance, and the NO3 - -N produced by NOB can receive electron supply faster, promoting the in-situ reduction of NO3 - -N, while increasing the contact possibility of the biological membrane and Fe 2+ , enhancing the expression of hemoglobin and nrfA enzyme, further promoting the electron transfer process and DNRA dissimilation process, and enhancing the nitrogen removal effect.

[0031] The thickness of the iron-carbon material layer 2 is in the range of 0.05 mm-0.15 mm, and the thickness of the hydrophobic organic membrane layer 3 is 0.5 mm or less. By such design, since the iron-carbon material layer 2 is suction-filtered to the surface of the hydrophobic organic membrane layer 3, its structure is very dense, and if its thickness exceeds 0.2 mm, the over-thick iron-carbon material layer 2 may crack or be uneven, affecting the subsequent water treatment effect. The thickness of the biological membrane layer 1 is preferably 400 μm-600 μm.

[0032] The frame 4 comprises a frame body and a plexiglass baffle, wherein the frame body is in a cuboid structure, the number of the membrane bodies is at least one, the plexiglass baffle is in a rectangular structure and is fixed on the outside of the frame body without the attached membrane body, and at least one plexiglass baffle is provided with an air inlet. In this way, the frame body is used to bear the membrane body, the frame body is preferably made of plexiglass, the plexiglass baffle provided with the air inlet is arranged close to the inner wall of the reactor body 8, and the air inlet is connected with a bomb joint. The membrane assembly 24 is fixed on the inner wall of the reactor body 8 through the bomb joint, and the connection between the membrane assembly 24 and the gas supply system is realized through the bomb joint, so as to realize the gas supply to the membrane assembly 24. Preferably, the number of the membrane bodies is two, which is more convenient for the bonding between the membrane body and the frame body. The number of the membrane bodies can also be three, four or five, so as to realize better water treatment effect.

[0033] A PN / A-MABR autotrophic denitrification device comprises the above-mentioned Fe / C-loaded membrane assembly, and further comprises a reactor body 8, a gas cylinder 20 and a magnetic stirrer 26, wherein the membrane assembly 24 is installed in the reactor body 8 and connected with the gas cylinder 20 through a gas supply pipeline 23, the magnetic stirrer 26 is arranged at the bottom end of the reactor body 8, and the reactor body 8 is provided with an inlet / outlet water port 17. In this way, the reactor body 8 is preferably made of plexiglass. The inside of the reactor body 8 is in a sealed state, and the connection with the external structure is sealed with blue silicone, so as to maintain the closed environment of the reactor body 8.

[0034] The number of the inlet / outlet water ports 17 can be one or two. When the number is one, it serves as both the water inlet and the water outlet. When the number is two, one serves as the water inlet and the other serves as the water outlet. The position of the inlet / outlet water port 17 is preferably the lower part of the reactor.

[0035] The membrane assembly 24 is preferably arranged in the middle part of the reactor body 8, and the number of the membrane assemblies 24 can be determined according to the volume of the reactor body 8 and / or the water inlet property. The membrane assembly 24 is preferably installed in the reactor body 8 through a bomb structure and connected with the gas supply pipeline 23, so as to realize the gas supply to the membrane assembly 24 and the reactor body 8 by the self-pressure of the gas cylinder 20.

[0036] The magnetic stirrer 26 is arranged to ensure that the biofilm fully contacts the reaction water.

[0037] The inlet / outlet water port 17 is connected with a water inlet tank 13 and a water outlet tank 14 through a pipeline.

[0038] The water inlet tank 13 is connected with the water inlet / outlet port 17 through the water inlet pipeline 11, the water outlet tank 14 is connected with the water inlet / outlet port 17 through the water outlet pipeline 12, the water inlet pipeline 11 is provided with the water inlet pump 9 and the water inlet valve 18, and the water outlet pipeline 12 is provided with the water outlet pump 10 and the water outlet valve 19. In this way, the water inlet stage of the reactor is controlled through the water inlet pump 9 and the water inlet valve 18, and the water outlet stage of the reactor is controlled through the water outlet pump 10 and the water outlet valve 19. The reactor, the water inlet tank 13 and the water outlet tank 14 constitute a reactor main body module, the membrane assembly 24 and the gas cylinder 20 constitute a gas supply module, and the magnetic stirrer 26 constitutes a complete mixing module.

[0039] The top end of the reactor main body 8 is an open end, and the top cover 15 is mounted on the top end. The gas supply pipeline 23 is provided with the pressure gauge 22, the flow meter 21 and the gas pipe valve 25. In this way, the gas supply pressure is monitored in real time through the pressure gauge 22, the gas flow is monitored in real time through the flow meter 21, and the gas supply is controlled through the gas pipe valve 25, so that the DO depth is conveniently controlled.

[0040] A preparation method of the membrane assembly, comprising the following steps: Step one, straw pretreatment: The straw is soaked in a ferric chloride solution, the straw and the ferric chloride form a mixture, the ratio (w / w) of the ferric chloride to the mixture is 45 / 100, and the soaking time is 2 h; the renewable and cheap biomass is converted into a Fe 3+ -containing catalytic precursor. The ferric chloride is dissociated into Fe 3+ / Fe 2+ in water, which can form a coordination bond or electrostatic adsorption with the hydroxyl and carboxyl in cellulose, hemicellulose and lignin; at the same time, the Lewis acidity of Fe 3+ can moderately break part of the glycosidic bonds, so that the straw surface is rough and the porosity is increased, thereby providing “self-catalytic” active sites for subsequent pyrolysis. The ratio of 45 / 100 is higher than the general biomass impregnation catalyst (1-20 wt%), and the purpose is to ensure sufficient iron dispersion and avoid insufficient Fe 0 / Fe3O4 / α-Fe nanoparticles from being formed at 600℃ due to insufficient Fe content; high loading can significantly improve the graphitization degree of the final biochar, and a large number of iron-containing functional groups are generated, thereby enhancing the magnetic properties and adsorption performance of the product.

[0041] Step two, drying treatment: The mixture obtained in step one is dried in an oven at 60℃ for 6 h; this is convenient for subsequent pyrolysis. Free water is slowly evaporated at a mild temperature (<100℃), thereby avoiding Fe 3+Agglomeration of Fe2O3particles into large particles due to rapid drying. Meanwhile, part of the coordinated water is retained, allowing Fe 3+ to remain in a highly dispersed state, and after drying, the straw assumes a tough "iron-cellulose composite film" structure.

[0042] Step three, pyrolysis in a tube furnace: The mixture after drying in step two is pyrolyzed in a tube furnace under N2atmosphere at 600℃ for 2 h with a heating rate of 10℃ / min. During the heating stage, depolymerization and dehydration of cellulose / hemicellulose occur at 200-350℃, generating a large amount of volatile organic fragments, Fe 3+ is partially reduced to Fe 2+ , catalyzing the deoxidation reaction and reducing tar production; at 350-500℃, the lignin aromatic units are broken, and Fe 2+ is further reduced to Fe 0 or Fe3O4nanocrystals by H2and CO produced by biomass pyrolysis; at 500-600℃, the volatile components are basically released, and Fe nanoparticles (5-20 nm) are uniformly embedded in the carbon matrix. During the constant temperature stage, complete reduction of Fe and graphitization are achieved, and at the same time, the newly formed micropores (<2 nm) are expanded into mesopores (2-50 nm), increasing the specific surface area, completely removing residual tar, and avoiding pore blockage.

[0043] Step four, preparation of the suspension: The mixture after pyrolysis in step three is dispersed in deionized water by ultrasonic treatment to obtain a suspension; the ultrasonic frequency is 40 kHz, and the time is 30 min. This allows the particles to fully depolymerize, avoiding "channeling" or "cracking" during filtration. The concentration of the suspension is controlled at 0.1-20 mg / mL.

[0044] Step five, vacuum filtration: The transmembrane pressure difference (usually 0.05-0.09 MPa) generated by vacuum is used to quickly and uniformly deposit the iron-carbon material in the suspension obtained in step four onto the surface of the hydrophobic organic membrane layer 3, forming an active layer with a controllable thickness (0.05-0.15 mm); the active layer is the iron-carbon material layer 2, and the loading of the iron-carbon material is 10-50 mg / cm 2 .

[0045] Step six, reactor assembly: The membrane body containing the iron-carbon material layer 2 and the hydrophobic organic film layer 3 obtained in step five is fixed on the frame 4 by adhesion to form a membrane assembly 24, then the membrane assembly 24 is installed in the reactor body 8, while being connected with the gas source, finally the reactor body 8 is sealed; the gas source is the gas cylinder 20, the membrane assembly 24 is put into the reactor body 8 from the top opening of the reactor body 8, and when the installation of the membrane assembly 24 is completed, the top cover 15 is sealed and fixed with the flange 16 on the reactor body 8 to complete the assembly of the reactor.

[0046] Step seven, reactor leak detection; an appropriate amount of water is added to the assembled reactor to cover the membrane assembly 24, and the reactor is placed for 24 h to detect whether the sealing property of the membrane assembly 24 is good, and the judgment method is whether water seeps into the inside of the membrane assembly 24.

[0047] Step eight, reactor biofilm formation: After the reactor leak detection is qualified, the nitritation sludge and the anammox sludge (the sludge concentration is 2000-4000 mg / L) are added into the reactor body 8, and the water in the reactor body 8 is fed (the NH4 + -N is 50-200 mg / L), then the reactor is operated in the SBR (sequencing batch reactor) mode at room temperature, the hydraulic retention time is 4-48 h, then air or pure oxygen is supplied into the membrane assembly 24, the dissolved oxygen concentration in the reactor body 8 is controlled to be below 0.5 mg / L, and after 1-4 weeks, when the brownish-brown biofilm is attached to the membrane assembly 24, it is determined that the reactor is successfully biofilm-formed.

[0048] A wastewater treatment method, using the above-mentioned PN / A-MABR autotrophic denitrification device, operating in the SBR mode, in one operation cycle, the raw water is fed into the reactor, the gas cylinder 20 is opened for continuous aeration, the aeration flow is maintained below 0.5 mL / min, and the dissolved oxygen concentration in the reactor is maintained below 0.5 mg / L, the speed of the magnetic stirrer 26 is controlled within 200-800 rpm in one operation cycle to realize the complete mixing of the water and the sludge in the reactor, after the operation is completed, the water in the reactor is discharged, and after one operation cycle, the next cycle of operation is started.

[0049] The wastewater in the reactor body 8 is coupled with the microorganism process in the biofilm attached to the surface of the membrane assembly 24 through the microelectrolysis process of the iron-carbon material layer 2 to realize the removal of pollutants in the water.

[0050] After each cycle, the effluent water sample is periodically collected for water quality determination, and the NH4 +The concentration of -N and TN is calculated, and the removal rates of the two kinds of nitrogen are further calculated, and the calculation results are shown in Table 1. Compared with the ordinary MABR-PN / A reactor, the effect of the present application is significantly improved. Under the premise of no organic matter addition, the removal rates of NH4 + The removal rates of -N and TN in the last stage are increased by 2.42% and 6.46%, respectively.

[0051] Table 1: Water quality results of the experiment

[0052] As shown in Table 1, the pollution removal effect of the present application is ideal, and compared with the MABR-PN / A, the PN / A-MABR autotrophic denitrification device of the present application has good stability, which provides a reference for the effective removal of NH4+-N and TN in low carbon-nitrogen ratio wastewater.

[0053] The specific steps of one operation cycle are as follows: Step one, running the aeration stage: open the gas pipe valve 25, the gas in the gas cylinder 20 or air enters the membrane assembly 24 through the gas supply pipeline 23, and then carries out bubbleless aeration into the reactor main body 8. The flow rate of the flow meter 21 is adjusted to be below 0.5 mL / min, and no aeration bubbles exist in the reactor. The aeration mode is continuous aeration or intermittent aeration.

[0054] Step two, running the water inlet stage: the water inlet valve 18 is opened, and under the action of the water inlet pump 9, the raw water enters the reactor main body 8 through the water inlet pipeline 11, and the water inlet time is controlled within 15 min; after the water inlet is completed, the water inlet pump 9 and the water inlet valve 18 are closed. This process can be completed through automatic control system or manual operation to ensure the accuracy and stability of water inlet.

[0055] Step three, wastewater treatment stage: the raw water in the water inlet stage submerges the membrane aeration membrane assembly 24 from top to bottom, and the residence time is 4-48 h. The oxygen or air provided by the membrane assembly 24 supports the metabolic process of the aerobic microorganisms in the inner layer of the biofilm, and at the same time maintains a low dissolved oxygen environment in the reactor main body 8; under the microelectrolysis of the iron-carbon material layer 2, electrons and Fe 2+ , etc. are generated in situ to promote the NO3 - dissimilation ability of the microorganisms in the inner layer of the biofilm, and strengthen the removal of part of the pollutants in the wastewater by the system; in addition, the Fe 2+ generated by the iron-carbon microelectrolysis promotes the expression of hemoglobin by the microorganisms and promotes the expression of enzymes related to the nitrogen metabolism process. The above processes simultaneously provide promotion for the efficient removal of pollutants in the wastewater.

[0056] Step four, running effluent stage: effluent valve 19 is opened, under the action of effluent pump 10, after a cycle of sewage is discharged to the effluent tank 14 through the effluent pipeline 12, the effluent time is also controlled within 15 min; after the effluent is completed, the effluent pump 10 and the effluent valve 19 are closed.

[0057] Step five, hydraulic retention time setting: the hydraulic retention time is one of the key factors affecting the sewage treatment effect. Longer hydraulic retention time can make the sewage in the reactor fully contact with the iron-carbon powder material and the biofilm, and improve the removal rate of pollutants, but it will also increase the land occupation area and operation cost of the reactor. Therefore, according to the complexity of the influent water quality and the treatment requirements, the appropriate hydraulic retention time can be selected, such as for high-concentration industrial wastewater, the hydraulic retention time can be appropriately extended to 24-48 h, and for low-concentration domestic sewage, the hydraulic retention time can be set to 4-24 h, to achieve the best sewage treatment effect and economic balance. In addition, in order to ensure that the biofilm and the sewage are fully contacted and reacted within the hydraulic retention time, the magnetic stirrer 26 is used to fully mix the sewage, and the speed of the magnetic stirrer 26 is usually set to 200-800 rpm.

[0058] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A Fe / C support-based membrane module, characterized by: The membrane assembly comprises a frame (4) and a membrane body attached to the outside of the frame (4), wherein the membrane body comprises a hydrophobic organic membrane layer (3), an iron-carbon material layer (2) and a biological membrane layer (1) arranged in sequence, and the hydrophobic organic membrane layer (3) is attached to the outside of the frame (4).

2. The Fe / C support-based membrane module according to claim 1, characterized by: The thickness of the iron-carbon material layer (2) is 0.05-0.15 mm, and the thickness of the hydrophobic organic membrane layer (3) is less than 0.5 mm.

3. The Fe / C support-based membrane module according to claim 1, wherein: The frame (4) comprises a frame body and a plexiglass baffle, wherein the frame body has a cuboid structure, the number of the membrane body is at least one, the plexiglass baffle has a rectangular structure and is fixed to the outside of the frame body without the membrane body, and at least one plexiglass baffle is provided with an air inlet.

4. A PN / A-MABR autotrophic denitrification device, characterized in that: The membrane assembly based on Fe / C loading comprises a reactor body (8), a gas cylinder (20) and a magnetic stirrer (26), wherein the membrane assembly (24) is installed in the reactor body (8) and connected with the gas cylinder (20) through a gas supply pipeline (23), the magnetic stirrer (26) is arranged at the bottom end of the reactor body (8), and the reactor body (8) is provided with an inlet / outlet water port (17).

5. The PN / A-MABR autotrophic denitrification device according to claim 4, characterized in that: The inlet / outlet water port (17) is connected with a water inlet tank (13) and a water outlet tank (14) through pipelines.

6. The PN / A-MABR autotrophic denitrification device according to claim 5, characterized in that: The water inlet tank (13) is connected with the inlet / outlet water port (17) through a water inlet pipeline (11), and the water outlet tank (14) is connected with the inlet / outlet water port (17) through a water outlet pipeline (12), the water inlet pipeline (11) is provided with a water inlet pump (9) and a water inlet valve (18), and the water outlet pipeline (12) is provided with a water outlet pump (10) and a water outlet valve (19).

7. The PN / A-MABR autotrophic denitrification device according to claim 4, characterized in that: The top end of the reactor body (8) is an open end, and a top cover (15) is arranged on the top end.

8. The PN / A-MABR autotrophic denitrification device according to claim 4, characterized in that: The gas supply pipeline (23) is provided with a pressure gauge (22), a flow meter (21) and a gas cylinder valve (25).

9. A method of making a membrane module according to any one of claims 1 to 3, characterised in that: The method comprises the following steps: Step one, straw pretreatment: The straw is soaked in a ferric chloride solution, the straw and the ferric chloride form a mixture, the ratio of ferric chloride to the mixture is 45 / 100, and the soaking time is 2 h; Step two, drying treatment: The mixture obtained in step one is dried in an oven at 60℃ for 6 h; Step three, tube furnace pyrolysis: The dried mixture in step two is pyrolyzed in a tube furnace under N2 atmosphere at a heating rate of 10℃ / min at 600℃ for 2 h; Step four, preparation of suspension: The pyrolyzed mixture in step three is ultrasonically dispersed in deionized water to obtain a suspension; Step five, vacuum filtration: The iron-carbon material in the suspension obtained in step four is quickly and uniformly deposited on the surface of the hydrophobic organic membrane layer (3) by the transmembrane pressure difference generated by vacuum to form an active layer with controllable thickness; Step six, reactor assembly: The membrane body containing the iron-carbon material layer (2) and the hydrophobic organic membrane layer (3) obtained in step five is fixed on the frame (4) by adhesion to form a membrane assembly (24), then the membrane assembly (24) is installed in the reactor body (8), an external gas source is connected, and finally the reactor body (8) is sealed; Step seven, reactor airtightness detection; Step eight, reactor membrane hanging: After the reactor airtightness detection is qualified, nitrosation sludge and anaerobic ammonia oxidation sludge are added into the reactor body (8), then the reactor is operated in SBR mode at room temperature, the hydraulic retention time is 4-48 h, then air is supplied into the membrane assembly (24), the dissolved oxygen concentration in the reactor body (8) is controlled to be below 0.5 mg / L, after 1-4 weeks, when brownish-brown biofilm is attached on the membrane assembly (24), it is determined that the reactor is successfully biofilmed.

10. A method of sewage treatment characterised by: The PN / A-MABR autotrophic denitrification device of any one of claims 4-8 is operated in SBR mode, in one operation cycle, raw water is fed into the reactor, the gas cylinder (20) is opened for continuous aeration, the aeration flow rate is maintained below 0.5 mL / min, and the dissolved oxygen concentration in the reactor is maintained below 0.5 mg / L, the speed of the magnetic stirrer (26) is controlled within 200-800 rpm in one operation cycle to realize complete mixing of the water and sludge in the reactor, after the operation is completed, the water in the reactor is discharged, and after one operation cycle is completed, the next cycle of operation is started.

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