Method for improving performance of methane production of microbial electrolysis cell biological cathode

Abstract

The present application relates to a kind of method for improving the performance of microbial electrolysis cell biological cathode methane production, comprising the following steps: (1) biological cathode multi-stage culture;(2) mature biological cathode multi-substrate metabolism;(3) microbial electrolysis cell energy synthesis optimization;(4) stable microbial electrolysis cell system operation.Compared with the prior art, the present application takes biological cathode as the core functional area of methane production, and aims at the key links involved in the stable operation of biological cathode culture, such as microbial enrichment, substrate metabolism strengthening, energy synthesis optimization, etc., and creatively proposes integrated strengthening technology.Compared with the existing technology which takes electrode material improvement and electron transfer promotion as the core, the present application cuts in from the core link directly related to methane production function, more accurately improves the ability and efficiency of biological cathode methane production metabolism, can effectively improve the performance of microbial electrolysis cell methane production, and can be used to meet the needs of biogas upgrading and carbon dioxide fixation, etc.

Description

Technical Field

[0001] This invention relates to the field of environmental protection and resource recycling technology, and in particular to a method for improving the methane production performance of the biocathode in a microbial electrolysis cell. Background Technology

[0002] In the field of wastewater and organic waste treatment, synergistic effects of pollution reduction and carbon reduction, along with enhanced resource and energy recovery, are key to achieving carbon emission reduction and even negative carbon emissions. Anaerobic bioconversion technology is a widely used green treatment technology for wastewater, sludge, and various organic wastes. It can achieve the harmless treatment of pollutants while recovering biomass resources and energy. However, it also has a series of problems, such as long treatment cycles, low biogas production efficiency, and low methane content in biogas. In recent years, microbial electrolyzers have been coupled into the anaerobic bioconversion process, offering a series of technical advantages such as enhanced organic matter hydrolysis and improved methanogenesis efficiency.

[0003] In the process of enhancing anaerobic biotransformation using microbial electrolysis cells, the performance of the biocathode determines the conversion efficiency of methanogenesis. For a long time, improving electron transfer performance has been considered a key factor in increasing the efficiency of methanogenesis at the cathode. Patents CN112441660A, "An apparatus and method for enhancing anaerobic digestion based on electron transfer coupled microbial electrolysis cells," and CN109179938A, "An anaerobic microbial electrochemical treatment process based on anode-promoted sludge anaerobic digestion and cathode carbon dioxide reduction," both focus on enhancing the biocathode reaction through electron transfer. However, the biomethanogenesis reaction at the cathode requires not only electron transfer but also a high microbial biomass load and enrichment of functional microorganisms in the cathode biofilm to drive efficient energy metabolism in the methanogenic microorganisms. Otherwise, simply enhancing the electron transfer process can easily lead to low biomass and low energy synthesis levels in the cathode biofilm, resulting in reduced reaction efficiency and system collapse. However, current research and development of biocathodes in microbial electrolysis cells lacks a method for enhancing biocathodes by increasing biomass load and enriching functional microorganisms.

[0004] Therefore, in order to promote the development and application of microbial electrolyzers in the field of anaerobic biotransformation, there is an urgent need for a new method to improve the methanogenic performance of the biocathode in microbial electrolyzers. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a method to improve the methanogenic performance of the biocathode in a microbial electrolysis cell. Through continuous multi-stage culture and multi-substrate metabolism, and through multi-stage culture screening, multi-substrate metabolism screening and energy synthesis optimization screening, the technical problems of low cathode biofilm loading and low abundance of functional microorganisms in the application of existing microbial electrolysis cells in anaerobic bioconversion are solved.

[0006] The objective of this invention can be achieved through the following technical solutions: The purpose of this invention is to provide a method for improving the methanogenesis performance of a biocathode in a microbial electrolysis cell, comprising the following steps: (1) Multi-stage cultivation of biocathode: The electrode material is first connected in an open circuit in a stable continuous flow anaerobic methanogenic environment. After the open circuit potential stabilizes, the circuit is closed and the electrode material is connected to the circuit cathode. After the current stabilizes, the biocathode is taken out and placed in the actual wastewater or waste environment to be treated. The open circuit connection and closed circuit connection process is repeated again to obtain a mature biocathode. (2) Multi-substrate metabolism of mature biological cathode: The mature biological cathode is connected in a closed circuit in a dual-chamber microbial electrolysis cell. The cathode chambers are respectively equipped with substrates such as acetic acid, carbon dioxide or sodium bicarbonate, or acetic acid mixed with carbon dioxide or sodium bicarbonate, etc., to enhance the methanogenesis of biological cathode with multiple substrates. (3) Optimization of energy synthesis in microbial electrolysis cell: The mature biological cathode after multi-substrate metabolism is placed in the actual wastewater or waste environment to be treated, and the ATP content of the cathode biofilm is tested. The proton concentration and pH of the system are simultaneously adjusted until the ATP content of the biofilm increases to a stable level. (4) Stabilize the operation of the microbial electrolysis cell system: Construct a stable microbial electrolysis cell system using the optimized biocathode obtained in step (3) and put it into formal operation.

[0007] Furthermore, the stable continuous-flow anaerobic methanogenic environment has a residence time of 10-40 days, a daily methane production fluctuation of no more than 5%, and a methane content of 50%-90% in the biogas.

[0008] Furthermore, the open-circuit potential is stable, with a daily average potential fluctuation of no more than 5%, and the current is stable, with a daily average current fluctuation of no more than 5%.

[0009] Furthermore, the wastewater or waste environment to be treated includes domestic sewage, sludge, kitchen waste, straw waste, livestock and poultry manure, etc.

[0010] Furthermore, the concentration range of acetic acid is 0.1-10 g / L, and the concentration range of sodium bicarbonate is 0.05-100 g / L.

[0011] Furthermore, the mature biological cathode exhibits a daily average biomass fluctuation of no more than 5% and a methane production fluctuation of no more than 5%.

[0012] Furthermore, the pH range is 6.8-7.8, the ATP content increases to a stable level, and the daily average ATP content fluctuation is no greater than 5%.

[0013] Furthermore, the stable microbial electrolysis cell system has a daily average current fluctuation of no more than 5% and a daily methane production fluctuation of no more than 5%.

[0014] Furthermore, the formal operation can be carried out in one of the following modes: batch operation, semi-continuous operation, or continuous operation.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) High cathode biofilm loading: Through continuous multi-stage culture and multi-substrate metabolism, the microbial loading capacity of cathode materials and the biomass of cathode biofilm can be effectively improved.

[0016] (2) High abundance of functional microorganisms: Through multi-stage culture screening, multi-substrate metabolism screening and energy synthesis optimization screening, functional microorganisms with high electrochemical activity, high metabolic activity and high energy synthesis ability can be effectively improved, thereby enhancing the cathodic methanogenesis performance.

[0017] (3) Wide range of applications: Through the construction of targeted and mature biological cathodes, it can be effectively applied to a variety of wastewater or waste environments and can operate continuously for a long time, with superior environmental and economic benefits.

[0018] (4) This invention uses the biocathode as the core functional area for methanogenesis. It creatively proposes an integrable enhancement technology for each key step involved in the cultivation and stable operation of the biocathode, including microbial enrichment, substrate metabolism enhancement, and energy synthesis optimization. Compared with existing technologies that focus on electrode material improvement and electron transport promotion, this invention addresses the core steps directly related to methanogenesis, more precisely improving the methanogenesis capacity and efficiency of the biocathode. This effectively enhances the methanogenesis performance of microbial electrolyzers and can be used to meet the needs of biogas upgrading and carbon dioxide fixation. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the method for improving the methane production performance of the biocathode in a microbial electrolysis cell according to the present invention. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0021] Example 1 The method for improving the methanogenesis performance of the biocathode in a microbial electrolysis cell, as described in this embodiment, is carried out according to the following steps: (1) The carbon felt material (commercially available product) is first connected in an open circuit in a stable continuous flow anaerobic methanogenic environment with a residence time of 25 days and a methane content of 70% in the biogas. After the open circuit potential stabilizes, the circuit is closed, and the electrode material is connected to the circuit cathode. After the current stabilizes, the carbon felt biocathode is taken out and placed in the actual sludge environment. The open circuit connection and closed circuit connection process is repeated to obtain a mature carbon felt biocathode. (2) The mature carbon felt biocathode is closed-circuited in a dual-chamber microbial electrolysis cell. The cathode chamber is subjected to methanogenic metabolism using a combination of three substrates: acetic acid, sodium bicarbonate, and acetic acid mixed with sodium bicarbonate. The concentration of acetic acid is 2.5 g / L and the concentration of sodium bicarbonate is 5 g / L. (3) The mature carbon felt biocathode after multi-substrate metabolism is placed in the actual sludge environment. The ATP content of the cathode biofilm is tested and the pH is controlled at 7.2 until the ATP content of the biofilm increases to a stable level. The daily average ATP content fluctuation is 3%. (4) The optimized carbon felt biocathode obtained in step (3) is used to construct a stable microbial electrolysis cell system. The daily average current fluctuation is 2% and the daily methanogenic fluctuation is 1%. The system is then put into formal operation.

[0022] Comparative Example 1 Using the same carbon felt material, step (1) is omitted.

[0023] This comparative method is carried out according to the following steps: (1) The carbon felt material was connected in a closed loop in a dual-chamber microbial electrolysis cell. The cathode chamber was subjected to methanogenic metabolism using a combination of three substrates: acetic acid, sodium bicarbonate, and a mixture of acetic acid and sodium bicarbonate. The concentration of acetic acid was 2.5 g / L and the concentration of sodium bicarbonate was 5 g / L. (2) The mature carbon felt biocathode after multi-substrate metabolism was placed in an actual sludge environment. The ATP content of the cathode biofilm was tested and the pH was kept stable at 7.2 until the ATP content of the biofilm increased to a stable level. The daily average ATP content fluctuation was 3%. (3) A stable microbial electrolysis cell system was constructed using the optimized carbon felt biocathode obtained in step (2). The daily average current fluctuation was 2% and the daily methanogenic production fluctuation was 1%. The system was then put into formal operation.

[0024] Comparative Example 2 Using the same carbon felt material, step (2) is omitted.

[0025] This comparative method is carried out according to the following steps: (1) The carbon felt material was first connected in an open circuit in a stable continuous flow anaerobic methanogenic environment with a residence time of 25 days and a methane content of 70% in the biogas. After the open circuit potential stabilized, the circuit was closed and the electrode material was connected to the circuit cathode. After the current stabilized, the carbon felt biocathode was taken out and placed in the actual sludge environment. The open circuit connection and closed circuit connection process was repeated to obtain a mature carbon felt biocathode. (2) The mature carbon felt biocathode was placed in the actual sludge environment and the ATP content of the cathode biofilm was tested. The pH was controlled at 7.2 until the ATP content of the biofilm increased to a stable level. The daily average ATP content fluctuation was 3%. (3) The optimized carbon felt biocathode obtained in step (2) was used to construct a stable microbial electrolysis cell system with a daily average current fluctuation of 2% and a daily methane production fluctuation of 1%. The system was then put into formal operation.

[0026] Comparative Example 3 Using the same carbon felt material, step (3) is omitted.

[0027] This comparative method is carried out according to the following steps: (1) The carbon felt material was first connected in an open circuit in a stable continuous flow anaerobic methanogenic environment with a residence time of 25 days and a methane content of 70% in the biogas. After the open circuit potential stabilized, the circuit was closed and the electrode material was connected to the circuit cathode. After the current stabilized, the carbon felt biocathode was taken out and placed in an actual sludge environment. The open circuit connection and closed circuit connection process was repeated to obtain a mature carbon felt biocathode. (2) The mature carbon felt biocathode was connected in a closed circuit in a dual-chamber microbial electrolysis cell. The cathode chambers were used for methanogenic metabolism with three substrate combinations: acetic acid, sodium bicarbonate, and acetic acid mixed with sodium bicarbonate. The concentration of acetic acid was 2.5 g / L and the concentration of sodium bicarbonate was 5 g / L. (3) A stable microbial electrolysis cell system was constructed using the mature carbon felt biocathode obtained in step (2) after multi-substrate metabolism. The daily average current fluctuation was 2% and the daily methane production fluctuation was 1%. The system was put into formal operation.

[0028] The biocathodes obtained in Example 1 and Comparative Examples 1, 2, and 3 were used in the anaerobic biotransformation process of sludge. Experimental results showed that the biofilm loading of the cathode in Example 1 was 115%, 44%, and 13% higher than that in Comparative Examples 1, 2, and 3, respectively. The abundance of functional electroactive bacteria and methanogens increased by 68%, 29%, and 16% compared to Comparative Examples 1, 2, and 3, respectively, and the final methanogenesis was increased by 37%, 21%, and 14% compared to Comparative Examples 1, 2, and 3, respectively. These results fully demonstrate the superior performance and technical effectiveness of the method for improving the methanogenesis performance of the biocathode in the microbial electrolysis cell presented in this technical solution.

[0029] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for improving the methanogenesis performance of a biocathode in a microbial electrolysis cell, characterized in that, Includes the following steps: (1) Multi-stage cultivation of biocathode: The electrode material is first connected in an open circuit in a stable continuous flow anaerobic methanogenic environment. After the open circuit potential stabilizes, the circuit is closed and the electrode material is connected to the circuit cathode. After the current stabilizes, the biocathode is taken out and placed in the actual wastewater or waste environment to be treated. The open circuit connection and closed circuit connection process is repeated again to obtain a mature biocathode. (2) Multi-substrate metabolism of mature biocathode: The mature biocathode obtained in step (1) is connected in a closed loop in a dual-chamber microbial electrolysis cell. The cathode chamber adopts a substrate combination method, and the multi-substrate enhances the methanogenic metabolism of the biocathode to obtain a mature biocathode after multi-substrate metabolism. (3) Optimization of energy synthesis in microbial electrolysis cell: The mature biocathode after multi-substrate metabolism is placed in the actual wastewater or waste environment to be treated, and the ATP content of the biofilm of the cathode is tested. The proton concentration and pH of the system are simultaneously adjusted until the ATP content of the biofilm increases to a stable level, and the optimized biocathode is obtained. (4) Stabilize the operation of the microbial electrolysis cell system: Construct a stable microbial electrolysis cell system using the optimized biocathode obtained in step (3) and put it into formal operation; The cathode chamber employs a multi-substrate combination as follows: the cathode chamber contains acetic acid, carbon dioxide or sodium bicarbonate, acetic acid mixed with carbon dioxide, or acetic acid mixed with sodium bicarbonate, among other combinations.

2. The method for improving the methanogenesis performance of a biocathode in a microbial electrolysis cell according to claim 1, characterized in that, The stable, continuous-flow anaerobic methanogenic environment has a residence time of 10-40 days, a daily methane production fluctuation of no more than 5%, and a methane content of 50%-90% in the biogas.

3. The method for improving the methanogenic performance of a biocathode in a microbial electrolysis cell according to claim 1, characterized in that, The open-circuit potential is stable, with a daily average potential fluctuation of no more than 5%, and the current is stable, with a daily average current fluctuation of no more than 5%.

4. The method for improving the methanogenesis performance of a biocathode in a microbial electrolysis cell according to claim 1, characterized in that, The wastewater or waste environment to be treated includes domestic sewage, sludge, kitchen waste, straw waste, and livestock and poultry manure.

5. The method for improving the methanogenesis performance of a biocathode in a microbial electrolysis cell according to claim 1, characterized in that, The concentration range of acetic acid is 0.1-10 g / L, and the concentration range of sodium bicarbonate is 0.05-100 g / L.

6. The method for improving the methanogenesis performance of a biocathode in a microbial electrolysis cell according to claim 1, characterized in that, The mature biological cathode exhibits a daily average biomass fluctuation of no more than 5% and a methane production fluctuation of no more than 5%.

7. The method for improving the methanogenic performance of a biocathode in a microbial electrolysis cell according to claim 1, characterized in that, The pH range is 6.8-7.8, the ATP content increases to a stable level, and the daily average ATP content fluctuation is no greater than 5%.

8. The method for improving the methanogenesis performance of a biocathode in a microbial electrolysis cell according to claim 1, characterized in that, The stable microbial electrolysis cell system has a daily average current fluctuation of no more than 5% and a daily methane production fluctuation of no more than 5%.

9. The method for improving the methanogenic performance of a biocathode in a microbial electrolysis cell according to claim 1, characterized in that, The formal operation will be carried out in one of the following modes: batch operation, semi-continuous operation, or continuous operation.

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