Apparatus and method for enriching anaerobic methanotrophic microorganisms using bubbleless aerated conductive membranes for denitrification

Abstract

The application provides a device and method for enriching anaerobic methane-oxidizing microorganisms by using a bubbleless aeration conductive membrane, and belongs to the technical field of environmental engineering. The device comprises an aeration membrane reactor, wherein the aeration membrane reactor comprises a shell, a water bath layer, an upper flange and a lower flange; an air inlet and an air outlet are arranged on the upper flange; the shell is provided with an aeration membrane with conductivity; the end of the air inlet located on the outer side of the shell is connected with a methane gas cylinder through a pipeline, and a gas pressure stabilizing valve and a first one-way flow device are arranged on the pipeline between the methane gas cylinder and the air inlet; and a water supply container for providing a liquid culture medium containing nitrogen oxides and an inoculum of DAMO bacteria for the reactor is connected with a circulating liquid inlet. The device and method can significantly promote the growth and metabolic rate of DAMO microorganisms through multiple reinforcements such as bubbleless aeration, biological retention and electrical activity.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering technology, and in particular relates to an apparatus and method for enriching denitrifying anaerobic methane-oxidizing microorganisms using a bubble-free aeration conductive membrane. Background Technology

[0002] Methane (CH4) is a potent greenhouse gas, contributing approximately 22% to global warming, second only to carbon dioxide. The methane oxidation process, through microbial action, converts methane into carbon dioxide, playing a crucial role in controlling global climate change. It is estimated that about 90% of methane produced in marine sediments is oxidized through anaerobic oxidation. Continuous or intermittent flooding conditions in freshwater wetlands, paddy fields, inland aquatic ecosystems, and coastal wetlands can also provide anoxic environments for the occurrence of anaerobic methane oxidation (AOM). Anaerobic methanogenic bacteria can bind AOM to various electron acceptors, such as nitrite (NO2), through multiple electron transport mechanisms. ), nitrates (NO3) ), metal oxides (Fe(III), Mn(IV) and AS(V)), sulfates (SO4) 2 ) and humus. The reaction in which methane is the electron donor and nitrite or nitrate is the electron acceptor is called denitrifying anaerobic methane oxidation (DAMO). DAMO archaea Candidatus 'Methanoperedens nitroreducens ( M. nitroreducens DAMO bacteria use methane as an electron donor to reduce nitrates to produce nitrites, and use methane as an electron donor to reduce nitrites to produce nitrogen gas.

[0003] CH4+4NO3 - →CO2 + 4NO2 - +2H2O(1)

[0004] 3CH4+8NO2 - +8H + →3CO2+4N2+10H2O(2) Greenhouse gas release and the need for external carbon sources for denitrification are two major challenges faced by urban wastewater treatment plants. The DAMO process has a dual effect of reducing nitrogen pollution and greenhouse gas emissions. Combining the DAMO process with existing wastewater treatment technologies provides a new approach to nitrogen pollution control and greenhouse gas emission reduction by achieving both denitrification and carbon reduction effects.

[0005] Although DAMO bacteria are widely distributed in the natural environment, they grow very slowly, with a generation time exceeding four weeks. Therefore, addressing the issues of slow growth and low metabolic rates in denitrifying anaerobic methanogenic microorganisms is urgently needed. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of slow growth and low metabolic rate of denitrifying anaerobic methane oxidizing microorganisms. It combines bubble-free aeration, conductivity, and the high surface area of ​​activated carbon. A conductive, bubble-free aeration membrane is placed in a bioreactor containing inoculum with DAMO bacteria and a liquid culture medium containing nitrate or nitrite. The aeration membrane is in communication with standard methane gas. Microorganisms attach to the aeration membrane filaments or the surface conductive particles of activated carbon and grow rapidly. Electron donor methane is supplied bubble-free through the membrane pores, and electron acceptors nitrate or nitrite dissolved in the solution are utilized through contact with the microorganisms.

[0007] This invention proposes a device for enriching denitrifying anaerobic methanogenic bacteria, comprising: An aerated membrane reactor includes a shell, a water bath layer disposed on the outside of the shell, an upper flange disposed at the top of the shell, and a lower flange disposed at the bottom of the shell. An air inlet and an air outlet are inserted into the upper flange. A circulating liquid inlet and a water bath layer inlet are located at the bottom of the shell, while a circulating liquid outlet and a water bath layer outlet are located at the top of the shell. An aerated membrane, which is conductive, is disposed inside the shell. The aerated membrane is open at its upper end and closed at its lower end, with the upper opening connected to the air inlet. A liquid seal mechanism is connected to the end of the air outlet located on the outside of the shell. The end of the air inlet located on the outside of the shell is connected to a methane cylinder via a pipeline. A gas pressure regulating valve and a first one-way flow device are sequentially installed on the pipeline between the methane cylinder and the air inlet. A water bath connected to the water bath layer inlet and outlet is disposed outside the shell. A water supply container connected to the circulating liquid inlet is disposed outside the shell to provide the reactor with inoculum for DAMO bacteria and a liquid culture medium containing nitrogen oxides.

[0008] Furthermore, the conductive aeration membrane includes an aeration membrane with a conductive material loaded on its surface, or an aeration membrane whose membrane filaments are doped with a conductive material. Preferably, the conductive material is activated carbon, activated carbon particles, graphene, or carbon fiber; More preferably, the conductive material is activated carbon.

[0009] Furthermore, conductive materials are doped into the membrane fibers of the aeration membrane, and bioelectrochemical reactors are added at the top and bottom of the aeration membrane.

[0010] Furthermore, a first one-way flow meter and a gas pressure regulating valve are used to control the gas phase partial pressure below the bubble point; Preferably, the methane supply pressure is controlled at 0.05~0.8 MPa.

[0011] Furthermore, a stirring magnet is provided at the bottom of the inner shell, and a magnetic stirrer is provided outside the shell to drive the stirring magnet to rotate; The upper flange is equipped with a pH electrode for detecting the pH of the solution inside the reactor and a temperature electrode for detecting the temperature of the solution inside the reactor. Preferably, the pH electrode is connected to a digital pH electrode display at the end located on the outside of the housing; the temperature electrode is connected to a digital temperature electrode display at the end located on the outside of the housing.

[0012] Furthermore, the air outlet is inserted into the liquid surface of the liquid sealing mechanism through a pipeline, and a second one-way flow device is provided on the pipeline; The temperature of the water in the water bath is controlled between 10 and 50°C. The circulating liquid inlet and circulating liquid outlet are connected by a pipeline, and a circulating pump is installed on the pipeline.

[0013] Furthermore, the water supply container provides the reactor with inoculum for DAMO bacteria and a liquid culture medium containing nitrogen oxides; preferably, the DAMO bacteria include DAMO bacteria and DAMO archaea.

[0014] The present invention also proposes a method for enriching denitrifying anaerobic methane-oxidizing microorganisms using any of the above-described devices.

[0015] Furthermore, the method includes: The water supply container contains inoculum containing DAMO bacteria and liquid culture medium containing nitrate or nitrite, which is pumped into the shell through the circulating liquid inlet by the water inlet pump; the methane cylinder provides methane gas, which is sent into the shell through the gas inlet via the gas pressure regulating valve and the first one-way flow device; the water bath provides constant temperature water, which enters the jacket of the reactor through the water bath inlet and exits through the water bath outlet back into the water bath; the gas outlet is connected to the liquid seal mechanism through the second one-way flow device; When a reaction occurs in the aerated membrane reactor, the conductive aeration membrane is used to maintain the partial pressure of the gas phase below the bubble point, and bubble-free aeration is introduced into the membrane bioreactor. Gas methane is used as an electron donor to reduce nitrite nitrogen and convert it into nitrogen and carbon dioxide for discharge. At the same time, microorganisms DAMO accumulate on the aeration membrane and grow to form a biofilm, so that the gas transfer in the aerated membrane reactor is within the membrane.

[0016] Furthermore, during the enrichment culture process, the nutrient solution was added separately, 3 to 4 times per month; During the enrichment culture, the pH was maintained between 6.0 and 9.0; The enrichment device is operated in an anaerobic environment; preferably, the anaerobic environment has a dissolved oxygen content of less than 0.20 mg / L.

[0017] This invention has the following advantages: This invention proposes a device for enriching denitrifying anaerobic methane-oxidizing microorganisms using a bubble-free aeration conductive membrane. The device includes an aeration membrane reactor, composed of a shell, an upper flange, and a lower flange. An air inlet and an air outlet are inserted into the upper flange. A conductive aeration membrane is installed inside the shell, with an open upper end and a closed lower end, the upper opening connected to the air inlet. A liquid seal mechanism is connected to the air outlet at the outer end of the shell to ensure an anaerobic environment. The air inlet at the outer end of the shell is connected to a methane cylinder. A gas pressure regulating valve and a first one-way flow device are sequentially installed between the methane cylinder and the air inlet to control bubble-free aeration into the reactor. A water supply container is located outside the shell to provide inoculum for DAMO bacteria and a liquid culture medium containing nitrogen oxides to the reactor. A water bath provides constant-temperature water to ensure the reaction proceeds under constant-temperature conditions.

[0018] This invention proposes a method for enriching denitrifying anaerobic methane-oxidizing microorganisms using a bubble-free aeration conductive membrane. The conductive aeration membrane is placed in a bioreactor containing inoculum containing DAMO bacteria and a liquid culture medium containing nitrate or nitrite. The aeration membrane is in communication with a standard methane gas phase. By maintaining the gas phase partial pressure below the bubble point through a gas pressure regulating valve and a first one-way flow device, bubble-free aeration can be ensured within the membrane bioreactor. During the reaction within the reactor, methane is used as an electron donor to reduce nitrite nitrogen, converting it into nitrogen gas and carbon dioxide, which are then discharged. Simultaneously, microorganisms accumulate on the aeration membrane, growing to form a biofilm, achieving solid-liquid separation and effectively reducing microbial loss. Furthermore, the gas transfer within the aeration membrane bioreactor occurs within the membrane system, increasing the contact time between the gas and liquid phases, thereby promoting the growth and metabolic rate of DAMO microorganisms. In addition, DAMO archaea possess the ability to transfer extracellular electrons; the bubble-free aeration conductive membrane can further enhance the electron transfer process in the DAMO biological system. It is evident that the method described in this invention can significantly promote the growth and metabolic rate of DAMO microorganisms through multiple enhancements such as bubble-free aeration, biological retention, and electroactivity. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the device provided by the present invention; Figure 2 These are the test results obtained from the test examples of this invention; in, Figure 1 Explanation of reference numerals in the attached diagram: Shell 1, aeration membrane 10, air inlet 11, air outlet 12, pH electrode 13, temperature electrode 14, water bath 110, water bath inlet 111, water bath outlet 112, upper flange 121, lower flange 122, circulating liquid inlet 131, circulating liquid outlet 132, circulating pump 133, magnetic stirrer 140, stirring magnet 141, methane cylinder 20, gas pressure regulating valve 21, first one-way flow device 22, liquid seal mechanism 30, second one-way flow device 31, water supply container 40, water inlet pump 41, water bath 50. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0022] The present invention will now be described in detail with reference to the accompanying drawings.

[0023] This invention provides an apparatus for enriching denitrifying anaerobic methanogenic bacteria, comprising: An aerated membrane reactor includes a shell 1, a water bath layer 110 disposed on the outside of the shell 1, an upper flange 121 disposed at the top of the shell 1, and a lower flange 122 disposed at the bottom of the shell 1; an air inlet 11 and an air outlet 12 are inserted into the upper flange 121; the lower part of the shell 1 is provided with a circulating liquid inlet 131 and a water bath layer inlet 111, and the upper part of the shell 1 is provided with a circulating liquid outlet 132 and a water bath layer outlet 112; an aeration membrane 10 is disposed inside the shell 1, the aeration membrane 10 is a conductive aeration membrane 10, the upper end of the aeration membrane 10 is open, the lower end is closed, and the upper end opening is connected to the lower end of the aeration membrane 10. The air inlet 11 is connected; the air outlet 12 is connected to a liquid seal mechanism 30 at the end located outside the shell 1; the end of the air inlet 11 located outside the shell 1 is connected to a methane cylinder 20 through a pipeline, and a gas pressure regulating valve 21 and a first one-way flow device 22 are successively installed on the pipeline between the methane cylinder 20 and the air inlet 11; a water bath 50 is provided outside the shell 1 and is connected to the water bath inlet 111 and the water bath outlet 112; a water supply container 40 is provided outside the shell 1 and is connected to the circulating liquid inlet 131 for providing the reactor with inoculum for DAMO bacteria and liquid culture medium containing nitrogen oxides.

[0024] In this invention, the inventors discovered through research that, besides their inherent characteristics, the most significant factor influencing the slow growth of DAMO microorganisms is the cultivation conditions. Methane supply is a limiting factor for DAMO microbial growth; using a bubble-free aeration method can ensure a sufficient supply of methane, the electron donor. Another factor contributing to the slow start-up of the DAMO system is biomass loss; effluent or sludge discharge during the cultivation process is detrimental to maintaining the system's biomass. Bubble-free aeration provides attachment space for biological growth, which is beneficial for maintaining the biomass of the reaction system. Furthermore, conductive aeration membranes, with conductive materials, can transfer electrons to microorganisms, promoting microbial metabolism and increasing the biodegradation rate. Alternatively, adding bioelectrochemical reactors at the top and bottom of the aeration membrane to provide voltage to the aeration membrane components can accelerate electron transfer, indirectly or directly providing an electron flow to the microorganisms. Applying an external auxiliary voltage can also promote the growth and metabolism of the DAMO biological system.

[0025] Specifically, compared with traditional foam aeration, bubble-free aeration has the following advantages: First, in bubble-free aeration, gas enters the biofilm through direct molecular diffusion, resulting in significantly higher mass transfer efficiency and 100% bioavailability, leading to higher biofilm activity. Therefore, gas solubility is no longer a limiting factor for microbial growth and metabolism in bubble-free aeration bioreactors. Second, in bubble-based aeration, friction between the rising gas and the biofilm causes it to detach from the carrier, a phenomenon completely absent in bubble-free aeration, resulting in stronger biofilm adhesion and less detachment. Third, bubble-free aeration reactors are more flexible because the gas and liquid phases are separated during bubble-free aeration, allowing for gas supply adjustment by varying the intramembrane pressure. Furthermore, bubble-free aeration consumes significantly less energy than bubble-based aeration, making it more economical.

[0026] In this embodiment of the invention, a first one-way flow meter 22 and a gas pressure regulating valve 21 are used to control the gas phase partial pressure below the bubble point. The first one-way flow meter 22 is used to control the flow rate, and the gas pressure regulating valve 21 is used to control the pressure. In one embodiment of the invention, by controlling the methane supply pressure at 0.05~0.8 MPa, methane aeration can be performed using a bubble-free aeration method.

[0027] In one embodiment of the present invention, a stirring magnet 141 is provided at the bottom of the inner shell 1, and a magnetic stirrer 140 for driving the stirring magnet to rotate is provided outside the shell. The stirring speed of the stirring magnet 141 is controlled at 100~1200 rpm.

[0028] In one embodiment of the present invention, the upper flange 121 is disposed at the top of the housing 1 and can be fixed to the top of the housing 1 with screws; the lower flange 25 is disposed at the bottom of the housing 1 and can be fixed to the bottom of the housing 1 with screws. A magnetic stirrer 140 is provided at the lower end of the lower flange, and stirring is completed by controlling the stirring magnet 141.

[0029] In one embodiment of the present invention, a pH electrode 13 for detecting the pH of the solution in the reactor and a temperature electrode 14 for detecting the temperature of the solution in the reactor are inserted on the upper flange 121.

[0030] In one embodiment of the present invention, the pH electrode 13 is connected to a pH electrode digital display at its outer end on the outer side of the housing; the temperature electrode 14 is connected to a temperature electrode digital display at its outer end on the outer side of the housing. The temperature and pH of the solution inside the reactor are detected in real time by the pH electrode 13 and the temperature electrode 14, and the data are displayed by the pH electrode digital display and the temperature electrode digital display.

[0031] In one embodiment of the present invention, the gas outlet 12 is inserted into the liquid surface of the liquid sealing mechanism 30 through a pipeline, wherein a second one-way flow device 31 is provided on the pipeline. The liquid sealing mechanism 30 can relieve the pressure inside the enrichment device and ensure the maintenance of an oxygen-free environment. The liquid sealing mechanism 30 includes a gas washing bottle filled with water.

[0032] In one embodiment of the present invention, the temperature of the water in the water bath 110 is controlled at 10~50℃. Water enters the water bath 110 from the water bath pot 50 through the water bath inlet 111 and returns to the water bath pot 50 from the water bath outlet 112, thus serving to maintain and keep the temperature constant. By controlling the temperature of the water bath 110 at 10~50℃, the internal temperature of the denitrification anaerobic methane oxidation enrichment device is controlled at 15~45℃; preferably 35℃.

[0033] In one embodiment of the present invention, the circulating liquid inlet 131 and the circulating liquid outlet 132 are connected by a pipeline, and a circulating pump 133 is provided on the pipeline. The circulating pump can increase the material circulation inside the reactor, so that the inoculum can adhere more fully to the membrane fibers.

[0034] Furthermore, the inoculum for DAMO bacteria and the liquid culture medium containing nitrogen oxides used to supply the reactor enter the shell to become the circulating liquid, and the circulation rate of the circulating liquid is 0.05~0.5 L / min.

[0035] In one embodiment of the invention, the water supply container 40 provides the reactor with inoculum for DAMO bacteria and a liquid culture medium containing nitrogen oxides. Preferably, the DAMO bacteria include DAMO bacteria and DAMO archaea.

[0036] Furthermore, the water supply container 40 can also provide denitrifying bacteria to the reactor. The denitrifying bacteria include, but are not limited to, those found in other contexts. IgnavibacteriumSP, Hyphomicrobium SP, Rhizobiaceae SP, Alicycliphilus SP.

[0037] Furthermore, the liquid culture medium comprises: mineral matrix: KHCO3 0.1-0.3 mg / L, KH2PO4 0.2-0.4 mg / L, CaCl2 0.2-0.4 mg / L, MgSO4 0.1-0.3 mg / L; acidic trace elements: FeSO4·7H2O 1.5-3.0 mg / L, ZnSO4·7H2O 0.05-0.15 mg / L, CoCl2·6H2O 0.1-0.2 mg / L, MnCl2·4H2O 0.3-1.0 mg / L, NiCl2·4H2O 0.2-0.5 mg / L, CuSO4 0.05-0.15 mg / L, H3BO3 0.005-0.02 mg / L; alkaline trace elements: SeO2 0.05-0.1 mg / L, Na2WO2·2H2O 0.05~0.1mg / L, Na2MoO40.2~0.3mg / L.

[0038] In this embodiment of the invention, the liquid culture medium enters the shell of the aerated membrane reactor from the circulating liquid inlet, and after passing through the aerated membrane, it forms a circulating liquid. After being discharged from the circulating liquid outlet, it passes through the circulating pump and enters the shell again from the circulating liquid inlet for reuse.

[0039] In one embodiment of the present invention, DAMO archaea (…) are attached to the aeration membrane reactor within the aeration membrane reactor. M. nitroreducens DAMO bacteria accounted for 0.1%–99% of the total bacterial count, with an abundance of 20–450 mg VSS / L; M. oxyfera The proportion of bacteria in the total bacterial count ranged from 0.1% to 99%, with an abundance of 15-380 mg VSS / L; DAMO archaea in circulating fluid ( M. nitroreducens It accounted for 0.1% to 99% of the total bacteria, with an abundance of 2.5 × 10⁻⁶. 2 —5.2×10 14 copies L -1 DAMO bacteria ( M. oxyfera The proportion of bacteria in the total bacterial count ranged from 0.1% to 99%, with an abundance of 6.8 × 10⁻⁶. 2 —1.0×10 14 copies L -1 .

[0040] Furthermore, during the enrichment culture process, the nutrient solution was added separately, 3-4 times per month. Regularly adding the nutrient solution reduced fluctuations in the microbial environment and provided a high-quality environment for the growth of denitrifying anaerobic methanogenic microorganisms.

[0041] Furthermore, the enrichment device is carried out in an anaerobic environment; preferably, the anaerobic environment has a dissolved oxygen content of less than 0.20 mg / L.

[0042] In one embodiment of the present invention, the aeration membrane 10 uses a microporous membrane or a dense membrane, and the membrane material is polyethylene, polyvinylidene fluoride, or polytetrafluoroethylene. Compared with other membrane materials, its rough surface is more conducive to the adhesion of microorganisms. As a hydrophobic membrane, oxygen only needs to diffuse through the membrane pores to reach the outer wall of the membrane during transport. Compared with hydrophilic microporous membranes where oxygen molecules are transported in the form of dissolved oxygen in the micropores, oxygen transport encounters less resistance.

[0043] In one embodiment of the present invention, the aeration membrane 10 is filled to a volume ratio of 5 to 70% of the shell 1.

[0044] In one embodiment of the present invention, the diameter of the membrane filaments of the aeration membrane 10 is typically selected between 0.1 mm and 2.0 mm. Finer filaments can provide a higher specific surface area, which is beneficial for oxygen transport. The number of filaments is 10-50, and the spacing between the filaments is 5 mm-50 mm.

[0045] In a preferred embodiment of the present invention, the conductive aeration membrane includes an aeration membrane with a conductive material loaded on its surface, or an aeration membrane with conductive material doped into its filaments.

[0046] Preferably, the conductive material is activated carbon, activated carbon particles, graphene, or carbon fiber.

[0047] More preferably, the conductive material is activated carbon. The activated carbon is made from organic raw materials (coal, wood, etc.), with a particle size of 8-16 mesh, a strength of 90-95%, a particle density of 0.35-0.55 g / cm³, and a pore size of 10-50 nm. Preferably, the surface area loading ratio of the membrane fibers on the aeration membrane is 0.5-30%.

[0048] In this embodiment of the invention, the conductive aeration membrane achieves two types of conductive modes: For aeration membranes loaded with conductive materials, the conductive materials are composited onto the surface of the aeration membrane; or for aeration membrane filaments doped with conductive materials, bioelectrochemical reactors are added to the top and bottom of the aeration membrane to provide voltage to the aeration membrane module.

[0049] Specifically, in this embodiment of the invention, the conductive aeration membrane achieves two conductive modes: Firstly, during the aeration membrane manufacturing process, activated carbon and other materials that promote electron transfer by microorganisms are added to the surface of the aeration membrane. Activated carbon with a rich porous structure is used as a methane adsorption material. Activated carbon with a large specific surface area can act as a container for adsorbing methane, continuously reducing the methane content in the reactor headspace, increasing the availability of methane in the enrichment device, and through the redox function of activated carbon, the ideal inherent conductivity and electron capacity can promote the transfer of electrons from methane oxidation by DAMO microorganisms. Secondly, bio-electrochemical reactors are added to the top and bottom of the aeration membrane to provide voltage to the aeration membrane module and accelerate electron transfer, indirectly or directly providing electron flow to microorganisms. Gas enters the cavities of the aeration membrane and then permeates out of the membrane wall, aiming to promote the rapid attachment and fixation of the biofilm to the surface of the aeration membrane. By using the membrane filaments as a carrier and improving the gas mass transfer characteristics, the enrichment of DAMO bacteria can be rapidly improved.

[0050] Furthermore, the cathode and anode of the bio-electrochemical reaction vessel are 5-20 cm apart.

[0051] Furthermore, the cathode and anode of the bio-electrochemical reaction vessel are independently selected from materials such as mesh or columnar stainless steel, carbon fiber, carbon felt, carbon cloth, and carbon rods. The mesh or columnar cathode / cathode can be folded or bent to increase the surface area; the system is started by controlling the anode potential within the range of 0~2000mV to improve the enrichment efficiency of electrogenic microorganisms.

[0052] The present invention also proposes a method for enriching denitrifying anaerobic methanogenic microorganisms using the above-mentioned device for enriching denitrifying anaerobic methanogenic bacteria.

[0053] In one embodiment of the present invention, the method includes: The water supply container 40 contains inoculum containing DAMO bacteria and liquid culture medium containing nitrate or nitrite, which is sent into the shell 1 through the circulating liquid inlet 131 by the water inlet pump 41; the methane cylinder 20 provides methane gas, which is sent into the shell 1 through the gas inlet 11 via the gas pressure regulating valve 21 and the first one-way flow device 22; the water bath 50 provides constant temperature water, which enters the jacket of the reactor through the water bath layer inlet 111 and exits through the water bath layer outlet 112 back into the water bath 50; the gas outlet 12 is connected to the liquid seal mechanism 30 through the second one-way flow device 31; When the reaction occurs in the aerated membrane reactor, methane is used as an electron donor to reduce nitrite nitrogen, which is converted into nitrogen gas and carbon dioxide and discharged. At the same time, microorganisms accumulate on the aeration membrane 10 and grow to form a biofilm, realizing solid-liquid separation and effectively reducing the loss of microorganisms. By using the conductive aeration membrane 10, when the gas phase partial pressure is maintained below the bubble point, bubble-free aeration can be introduced into the membrane bioreactor, so that the gas transfer in the membrane aerated bioreactor is within the membrane system.

[0054] Experimental Example 1 Testing the microbial enrichment effect of the device of the present invention Before reactor operation, 1L of prepared liquid culture medium was taken and dissolved oxygen was removed by blowing with 99% nitrogen to maintain an anaerobic environment. The pH of the liquid culture medium was adjusted to approximately 7.5 using 1mmol / L NaOH. 95% methane and 5% carbon dioxide from the gas cylinder were continuously fed into the reactor through the aeration membrane in a bubble-free aeration manner, controlled by the methane gas manifold (methane supply pressure controlled at 0.5 MPa) and the first one-way flow device (0.01~0.5L / min).

[0055] The liquid culture medium consists of: Mineral matrix: KHCO3 0.2 mg / L, KH2PO4 0.3 mg / L, CaCl2 0.3 mg / L, MgSO4 0.2 mg / L; Acidic trace elements: FeSO4·7H2O 2.0 mg / L, ZnSO4·7H2O 0.1 mg / L, CoCl2·6H2O 0.15 mg / L, MnCl2·4H2O 0.5 mg / L, NiCl2·4H2O 0.4 mg / L, CuSO4 0.1 mg / L, H3BO3 0.01 mg / L; Alkaline trace elements: SeO2 0.08 mg / L, Na2WO2·2H2O 0.08 mg / L, Na2MoO4 0.25 mg / L.

[0056] The concentration of nitrite nitrogen in the reactor was measured every two days using ultraviolet ion chromatography. The nitrite nitrogen concentration in the liquid culture medium was kept constant at 30 mg-N / L. When the nitrite nitrogen concentration in the reactor fell below 5 mg-N / L, the liquid culture medium needed to be replaced with fresh medium promptly. The reactor was operated at a constant temperature of 35°C.

[0057] This batch of experiments lasted for two weeks, during which the effects of different conductive methods (conductivity mode 1 involved adding activated carbon to the surface of the aeration membrane; conductivity mode 2 involved adding bio-electrochemical reactors at the top and bottom of the aeration membrane to provide voltage to the aeration membrane) on microbial metabolic activity were investigated. The experimental results are as follows. Figure 2 As shown.

[0058] Depend on Figure 2 It can be seen that, compared with the control group, both different power application methods can promote the growth of bacterial metabolic activity in the reactor: conductive mode 1 can increase bacterial metabolic activity by about 75%, and conductive mode 2 can increase bacterial metabolic activity by about 100%. This demonstrates that applying electricity can significantly enhance the growth of bacterial metabolic activity.

[0059] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for enriching denitrifying anaerobic methanogenic microorganisms, characterized in that, The apparatus used in the method includes: An aerated membrane reactor includes a shell, a water bath layer disposed on the outside of the shell, an upper flange disposed at the top of the shell, and a lower flange disposed at the bottom of the shell. An air inlet and an air outlet are inserted into the upper flange. A circulating liquid inlet and a water bath layer inlet are located at the bottom of the shell, while a circulating liquid outlet and a water bath layer outlet are located at the top of the shell. An aerated membrane, which is conductive, is disposed inside the shell. The aerated membrane is open at the top and closed at the bottom, with the top opening connected to the air inlet. A liquid seal mechanism is connected to the end of the air outlet located on the outside of the shell. The end of the air inlet located on the outside of the shell is connected to a methane cylinder via a pipeline. A gas pressure regulating valve and a first one-way flow device are sequentially installed on the pipeline between the methane cylinder and the air inlet. A water bath connected to the water bath layer inlet and outlet is disposed outside the shell. A water supply container connected to the circulating liquid inlet is disposed outside the shell to provide the reactor with inoculum for DAMO bacteria and a liquid culture medium containing nitrates or nitrites. Among them, the conductive aeration membrane includes an aeration membrane with conductive material loaded on its surface, or an aeration membrane with conductive material doped into its membrane filaments; for the aeration membrane with conductive material doped into its membrane filaments, a bioelectrochemical reactor is added to the top and bottom of the aeration membrane to provide voltage to the aeration membrane; A first one-way flow meter and a gas pressure regulating valve are used to control the gas phase partial pressure below the bubble point; the methane supply pressure is controlled at 0.05~0.8MPa to achieve bubble-free aeration. The method includes: The water supply container contains inoculum containing DAMO bacteria and liquid culture medium containing nitrate or nitrite, which is pumped into the shell through the circulating liquid inlet by the water inlet pump; the methane cylinder provides methane gas, which is sent into the shell through the gas inlet via a gas pressure regulating valve and a first one-way flow device; the water bath provides constant temperature water, which enters the jacket of the reactor through the water bath layer inlet and exits through the water bath layer outlet back into the water bath; the gas outlet is inserted into the liquid surface of the liquid sealing mechanism through a pipeline equipped with a second one-way flow device; the gas outlet is connected to the liquid sealing mechanism through the second one-way flow device; When a reaction occurs in the aerated membrane reactor, the conductive aeration membrane is used to maintain the partial pressure of the gas phase below the bubble point, and bubble-free aeration is introduced into the aerated membrane reactor. Gas methane is used as an electron donor to reduce nitrite nitrogen and convert it into nitrogen and carbon dioxide for discharge. At the same time, microorganisms DAMO accumulate on the aeration membrane and grow to form a biofilm, so that the gas transfer in the aerated membrane reactor is within the membrane.

2. The method according to claim 1, characterized in that, The conductive material is activated carbon, manganese particles, graphene, or carbon fiber.

3. The method according to claim 1, characterized in that, The bottom of the housing is provided with a stirring magnet, and the outside of the housing is provided with a magnetic stirrer for driving the stirring magnet to rotate; The upper flange is equipped with a pH electrode for detecting the pH of the solution inside the reactor and a temperature electrode for detecting the temperature of the solution inside the reactor.

4. The method according to claim 3, characterized in that, The pH electrode is located at the outer end of the housing and is connected to a digital pH electrode display; the temperature electrode is located at the outer end of the housing and is connected to a digital temperature electrode display.

5. The method according to claim 1, characterized in that, The temperature of the water in the water bath is controlled between 10 and 50°C. The circulating liquid inlet and circulating liquid outlet are connected by a pipeline, and a circulating pump is installed on the pipeline.

6. The method according to claim 1, characterized in that, The DAMO bacteria include DAMO bacteria and DAMO archaea.

7. The method according to claim 1, characterized in that, During the enrichment culture process, the nutrient solution is added separately, 3-4 times per month. During the enrichment culture, the pH was maintained between 6.0 and 9.0; The enrichment device was placed in an anaerobic environment; the anaerobic environment was defined as a dissolved oxygen content of less than 0.20 mg / L.

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