Bioelectrochemical electrodes and their applications in bioelectrochemical devices for treating refractory wastewater

Abstract

The present invention discloses a bioelectrochemical electrode and its application in a bioelectrochemical device for treating refractory wastewater. The bioelectrochemical electrode comprises an anode and a cathode arranged opposite to each other, and an insulating plastic barrier layer arranged between the anode and the cathode, wherein the anode, the insulating plastic barrier layer and the cathode are sequentially stacked and bonded together; the anode and the cathode are each formed with at least two arc-shaped sub-electrodes; and the central angle of each arc-shaped sub-electrode in the anode and the cathode is independently 120°-180°; a straight electrode is formed between each pair of adjacent arc-shaped sub-electrodes in the anode and the cathode; the material of the anode and the cathode is stainless steel fiber felt; after application of the bioelectrochemical electrode of the present invention, dead bacteria and the like can be effectively removed under the action of water flow, the formation and stability of electrochemically active bacterial biofilm can be promoted, a higher current density can be obtained, and the biodegradability of the wastewater can be effectively improved.

Description

[0001] This invention is a divisional application of the Chinese invention patent application with application date of April 26, 2021, application number 2021104520876, and name “A bioelectrochemical electrode with an arc structure and its application”. Technical Field

[0002] The present invention relates to the field of microbial electrochemical technology, and in particular to a bioelectrochemical electrode and its application in a bioelectrochemical device for treating refractory wastewater. The bioelectrochemical electrode can improve the biodegradability of refractory wastewater. Background Art

[0003] As a sustainable technology that balances wastewater treatment and energy generation, bioelectrochemical systems have demonstrated significant potential for the pretreatment of refractory wastewater. The system's operating principle is that electrochemically active bacteria at the anode oxidize organic substrates in the wastewater, generating electrons that are then transferred via an external circuit to the cathode, where they cause the reduction of refractory substances, achieving efficient removal of refractory pollutants. Furthermore, applying an additional voltage can enhance the targeted degradation of organic matter in the wastewater. Consequently, this system offers the advantages of low external energy requirements and high treatment efficiency.

[0004] Electrodes are key components of the structure and function of bioelectrochemical systems, promoting electron transfer by electrochemically active bacteria and thereby accelerating the degradation of recalcitrant pollutants. The anode provides a site for electrochemically active microbial metabolism and reduces the cathode potential through anodic reactions, indirectly affecting pollutant degradation efficiency. The cathode, as an electron donor, directly influences the reduction efficiency of recalcitrant pollutants. Like the anode, the cathode also has a significant impact on the biofilm formed by microbial-electrode interactions. Generally, electrode surface reactions are largely determined by the properties of the electrode material used. Over the past few decades, electrodes have been primarily constructed from carbon-based materials, such as carbon brushes, carbon cloth, carbon fiber felt, and graphite particles. These materials offer high surface area, corrosion resistance, biocompatibility, and stability. Furthermore, numerous studies have reported on modifying the properties of stainless steel using methods such as nitrogen doping, carbon nanotube loading, and conductive polymer modification. However, both traditional carbon-based materials and modified stainless steel electrodes suffer from limitations such as limited economic feasibility, making them difficult to apply in large-scale pretreatment of recalcitrant wastewater. Furthermore, they suffer from low bioretention and poor treatment efficiency. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an improved bioelectrochemical electrode and its application in a bioelectrochemical device for treating refractory wastewater. The new bioelectrochemical electrode can improve the biodegradability of refractory wastewater, and can solve one or more technical problems existing in the above-mentioned prior art, and at least provide a beneficial option or create conditions.

[0006] In order to achieve the above object, a technical solution adopted by the present invention is:

[0007] A bioelectrochemical electrode with an arc-shaped structure comprises an anode and a cathode arranged opposite to each other, wherein the anode and the cathode are respectively formed with at least one arc-shaped sub-electrode; and the central angle of each arc-shaped sub-electrode in the anode and the cathode is independently 60°-180°.

[0008] According to some preferred aspects of the present invention, the central angle of each of the arc-shaped sub-electrodes is independently 120°-180°.

[0009] In the present invention, if the central angle of each of the arc-shaped sub-electrodes is less than 60°, the improvement in biological retention is not obvious, the biocompatibility is poor, and it is difficult to promote the formation of electrochemically active bacterial biofilms; if the central angle of each of the arc-shaped sub-electrodes is greater than 180°, it will cause the accumulation of dead bacteria, impurity bacteria, suspended particles, etc., hindering the enrichment of electrochemically active bacteria and seriously reducing the electron transfer rate.

[0010] According to some preferred aspects of the present invention, the anode and the cathode are respectively formed with at least two arc-shaped sub-electrodes, and in the anode and the cathode, a straight electrode is formed between each of the adjacent arc-shaped sub-electrodes. The straight electrode can avoid interference between adjacent arc-shaped sub-electrodes, and at the same time reserve a position for later fixing the anode and cathode.

[0011] According to some preferred aspects of the present invention, the anode and the cathode are parallel to each other.

[0012] According to some preferred aspects of the present invention, the distance between the anode and the cathode is 0.001-3 mm.

[0013] According to some preferred aspects of the present invention, the bioelectrochemical electrode further comprises an insulating plastic separator disposed between the anode and the cathode.

[0014] According to some preferred aspects of the present invention, the thickness of the insulating plastic barrier is 0.001-3 mm.

[0015] According to some preferred aspects of the present invention, the anode, the insulating plastic separator and the cathode are stacked and laminated in sequence.

[0016] In the present invention, the distance between the anode and the cathode can be determined by the thickness of the insulating plastic interlayer, that is, when the anode, the insulating plastic interlayer and the cathode are stacked and bonded in sequence, the distance between the anode and the cathode is the thickness of the insulating plastic interlayer; and the insulating plastic interlayer can prevent the anode and the cathode from directly short-circuiting during use, and can also improve the stability of the overall relative position relationship.

[0017] According to some preferred aspects of the present invention, the bioelectrochemical electrode further comprises a fixing member for fixing the anode, the cathode and the insulating plastic barrier relative to each other, and the fixing member is made of insulating material.

[0018] In some embodiments of the present invention, the fixing member may be an insulating plastic cable tie, which is fixed by perforating the insulating plastic cable tie.

[0019] According to some preferred aspects of the present invention, the anode and cathode are both made of stainless steel fiber felt, which is more economical and corrosion-resistant than traditional carbon-based electrodes; more biocompatible and conductive than ordinary stainless steel mesh; and more economical, easily available, and highly operable. In some embodiments of the present invention, the stainless steel fiber felt can be 316 stainless steel fiber felt with a filtration accuracy of 400 μm.

[0020] Another technical solution provided by the present invention is a bioelectrochemical device for treating refractory wastewater, the device comprising the above-mentioned bioelectrochemical electrode with an arc structure, wherein the anode and the cathode extend in vertical directions respectively.

[0021] According to some preferred aspects of the present invention, the bioelectrochemical electrodes are disposed in an anaerobic reactor; more preferably, the anaerobic reactor is an upflow anaerobic sludge blanket having a height-to-diameter ratio of 5-15:1.

[0022] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0023] Based on the problems of poor economic feasibility, biological retention, and treatment efficiency of bioelectrochemical electrodes in the prior art, the present invention innovatively provides an improved anode and cathode electrodes provided with arc-shaped sub-electrodes, and limits the central angle of each arc-shaped sub-electrode to independently 60°-180°. This not only improves the biocompatibility of the electrode, but also can effectively remove dead bacteria, impurity bacteria, and suspended particles under the action of water flow, thereby promoting the formation and stability of electrochemically active bacterial biofilms. At the same time, the anode and cathode electrodes of the present invention can be set closer, which accelerates the electron transfer efficiency between the electrodes and obtains a higher current density, so that the electrodes of the present invention can be used in the pretreatment of difficult-to-degrade wastewater, which can effectively improve the biodegradability of the wastewater and alleviate the treatment burden for the back-end biological treatment section. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 Schematic diagram of the structure of the bioelectrochemical electrode with an arc structure according to Example 1 of the present invention;

[0026] Figure 2 for Figure 1 A magnified schematic diagram of point A;

[0027] In Example 1, 1, anode; 2, cathode; 3, insulating plastic barrier; 4, insulating plastic tie; a1, arc-shaped sub-electrode of anode; a2, arc-shaped sub-electrode of cathode; b1, straight electrode of anode; b2, straight electrode of cathode; center angle, α;

[0028] Figure 3 Schematic diagram of the structure of a bioelectrochemical electrode with an arc structure according to Example 2 of the present invention;

[0029] In Example 2, 1', anode; 2', cathode; 3', insulating plastic barrier; 4', insulating plastic tie; center angle, α';

[0030] Figure 4 Schematic diagram of the structure of the bioelectrochemical electrode with an arc structure according to Example 3 of the present invention;

[0031] Among them, in Example 2, 1", anode; 2", cathode; 3", insulating plastic barrier; 4", insulating plastic tie; central angle, α". DETAILED DESCRIPTION

[0032] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The following description sets forth many specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] In the description of the present invention, “a plurality of” means at least two, for example, two, three, etc., unless otherwise clearly and specifically defined.

[0034] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0035] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0036] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element.

[0037] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] Based on the problems of poor economic feasibility, bioretention, and treatment efficiency of bioelectrochemical electrodes in the prior art, the present invention innovatively provides a bioelectrochemical electrode with an arc structure, which includes an anode and a cathode arranged opposite to each other, and the anode and the cathode are respectively formed with at least one arc-shaped sub-electrode; and in the anode and the cathode, the central angle of each arc-shaped sub-electrode is independently 60°-180°, preferably 120°-180°.

[0039] In the present invention, if the central angle of each of the arc-shaped sub-electrodes is less than 60°, there is no obvious improvement in biological retention, and the biocompatibility is poor, and it is difficult to promote the formation of electrochemically active bacterial biofilms. If the central angle of each of the arc-shaped sub-electrodes is greater than 180°, it will cause the accumulation of dead bacteria, impurity bacteria, waste, etc., hindering the enrichment of electrochemically active bacteria and seriously reducing the electron transfer rate.

[0040] Preferably, the anode and the cathode are respectively formed with at least two arc-shaped sub-electrodes, and in the anode and the cathode, a straight electrode is formed between the adjacent arc-shaped sub-electrodes. The straight electrode can avoid interference between adjacent arc-shaped sub-electrodes, and at the same time reserve position for later fixing of the anode and cathode.

[0041] Preferably, the anode and the cathode are parallel to each other, and the distance between the anode and the cathode is 0.001-3 mm.

[0042] Preferably, the bioelectrochemical electrode further comprises an insulating plastic barrier layer provided between the anode and the cathode, the thickness of the insulating plastic barrier layer is 0.001-3 mm, and the anode, the insulating plastic barrier layer and the cathode are sequentially stacked and bonded.

[0043] In the present invention, the distance between the anode and the cathode can be determined by the thickness of the insulating plastic interlayer, that is, when the anode, the insulating plastic interlayer and the cathode are stacked and bonded in sequence, the distance between the anode and the cathode is the thickness of the insulating plastic interlayer; and the insulating plastic interlayer can prevent the anode and the cathode from directly short-circuiting during use, and can also improve the stability of the overall relative position relationship.

[0044] Furthermore, the bioelectrochemical electrode further comprises a fixing member for fixing the anode, the cathode and the insulating plastic barrier relative to each other, wherein the fixing member is made of an insulating material, and specifically, the fixing member can be an insulating plastic tie, which is fixed by perforating the insulating plastic tie.

[0045] Preferably, the anode and cathode are both made of stainless steel fiber felt, which is more economical and corrosion-resistant than traditional carbon-based electrodes, more biocompatible and conductive than ordinary stainless steel mesh, and more economical, easily available, and highly operable. In some embodiments of the present invention, the stainless steel fiber felt can be 316 stainless steel fiber felt with a filtration accuracy of 400 μm.

[0046] The present invention also provides an application of the above-mentioned bioelectrochemical electrode with an arc structure, and is applied to a bioelectrochemical device for treating refractory wastewater. The device includes the above-mentioned bioelectrochemical electrode, and the anode and the cathode extend in the vertical direction respectively.

[0047] Preferably, the bioelectrochemical electrode is arranged in an anaerobic reactor; more preferably, the anaerobic reactor is an upflow anaerobic sludge bed with a height-to-diameter ratio of 5-15:1. The above-mentioned bioelectrochemical electrode with an arc structure can be matched with such an upflow anaerobic sludge bed with a relatively large height-to-diameter ratio, and the matching effect is better.

[0048] Specifically, in the present invention, the above-mentioned bioelectrochemical electrode with an arc-shaped structure (hereinafter also referred to as a bioelectrochemical electrode with an arc-shaped sub-electrode) can be prepared using existing conventional methods. For example, the stainless steel fiber felt can be cut to specific requirements, and then roughly shaped by pressing with a cylindrical roller to form a stainless steel fiber felt electrode with an arc-shaped side. Finally, it is fixed with an insulating plastic interlayer and the excess part is cut off.

[0049] Meanwhile, in the present invention, the bioelectrochemical electrode having the arc-shaped sub-electrodes is applied to a bioelectrochemical device to treat refractory wastewater by the following method, specifically comprising:

[0050] 1) Pretreatment of the bioelectrochemical electrode with the arc-shaped sub-electrode: first rinse the surface impurities with deionized water, air-dry naturally, and then soak in acetone solution for 12 hours. After the electrode is air-dried, soak in 5% sulfuric acid solution for 2 hours. Finally, rinse with deionized water and place in a clean place for use.

[0051] 2) Constructing a bioelectrochemical system: placing the bioelectrochemical electrode with the arc-shaped sub-electrode treated in step (1) into a bioelectrochemical reactor, such as an upflow anaerobic sludge blanket, and leading a section of wire with a titanium wire to connect to a DC power supply, and providing a fixed resistor and a reference electrode.

[0052] 3) Start the bioelectrochemical system: inoculate anaerobic activated sludge into the reactor, use a peristaltic pump to pump the difficult-to-degrade wastewater into the reactor, and use a DC power supply to provide voltage to achieve the purpose of improving the biodegradability of the difficult-to-degrade wastewater.

[0053] More preferably, the anaerobic activated sludge is taken from the actual difficult-to-degrade wastewater UASB, with a sludge concentration of 2000-3000 mg / L; the hydraulic retention time controlled by the peristaltic pump is 12 hours; the DC power supply provides a voltage of 0.5V; and the biochemical property of the difficult-to-degrade wastewater is BOD5 / COD=0.1-0.2.

[0054] Specifically, the present invention is further described below in conjunction with three embodiments.

[0055] Example 1:

[0056] A bioelectrochemical electrode with an arc-shaped sub-electrode was constructed: 316 stainless steel fiber felt with a filtration accuracy of 400 μm was selected and cut into two pieces of stainless steel fiber felt with a size of L×B (length×width)=133.8×40 mm. One piece was roughly shaped by pressing with a cylindrical roller with a radius of 20 mm, and the other piece was roughly shaped by pressing with a cylindrical roller with a radius of 22 mm to form an electrode with an arc-shaped sub-electrode. Finally, the electrode was fixed to the insulating plastic partition 3 with an insulating plastic tie 4 through perforations, and the excess part was further cut off.

[0057] like Figure 1-2 As shown, the overall electrode has 4 arc-shaped sub-electrodes with a radius of 20 mm (possessed by the cathode 2) and 4 arc-shaped sub-electrodes with a radius of 22 mm (possessed by the anode 1), and a central angle α of 60° (specifically, in the anode 1, it can be simply referred to as the arc-shaped sub-electrode a1 of the anode; in the cathode 2, it can be simply referred to as the arc-shaped sub-electrode a2 of the cathode); in the anode or cathode, a straight line electrode is formed between every two adjacent arc-shaped sub-electrodes (specifically, in the anode 1, it can be simply referred to as the straight line electrode b1 of the anode; in the cathode 2, it can be simply referred to as the straight line electrode b2 of the cathode). In this example, the length of the straight line electrode is set to 10 mm; deionized water is used to rinse impurities on the electrode surface, and after natural air drying, it is placed in an acetone solution for 12 hours. After the electrode is air-dried, it is placed in a 5% sulfuric acid solution for 2 hours. Finally, it is washed with deionized water and placed in a clean place. Similarly, an insulating plastic spacer 3 with a thickness D of 2 mm and the same size parameters and configuration as the electrodes is placed between the positive and negative electrodes, and an insulating plastic tie 4 is used to further fix the two electrodes and the insulating plastic spacer 3 through holes to avoid contact between the electrodes.

[0058] Constructing a bioelectrochemical reactor: The above-described arc-shaped sub-electrode-shaped bioelectrochemical electrode was placed in a bioelectrochemical reactor. A 1mm-diameter titanium wire was used to extend a lead wire connected to a DC power supply. A 10Ω resistor and a saturated calomel reference electrode were also installed. The bioelectrochemical reactor was then started: anaerobic activated sludge was inoculated into a UASB reactor (with a height-to-diameter ratio of 10) to a sludge concentration of approximately 2500 mg / L. Refractory wastewater with a BOD5 / COD ratio of 0.15 was pumped into the reactor using a peristaltic pump. The hydraulic retention time was controlled at 12 hours, and a DC power supply provided a voltage of 0.5V.

[0059] Example 2:

[0060] The difference between this embodiment and embodiment 1 is that the size of the cut stainless steel fiber felt is L×B=217.6×40 mm, and the electrode formed later has four arc-shaped sub-electrodes with a radius of 20 mm, four radius of 22 mm and a central angle of 120°. The other steps are consistent with embodiment 1 (specifically, Figure 3 As shown, in this electrode, the anode is marked with 1′, the cathode is marked with 2′, the insulating plastic barrier is marked with 3′; the insulating plastic tie is marked with 4′; and the central angle is marked with α′).

[0061] Example 3:

[0062] The difference between this embodiment and embodiment 1 is that the size of the cut stainless steel fiber felt is L×B=331.3×40 mm, and the electrode formed later has a total of 4 arcs with a radius of 20 mm, 4 arcs with a radius of 22 mm and a central angle of 180°; the other steps are consistent with embodiment 1 (specifically, Figure 4 As shown, in this electrode, the anode is marked with 1", the cathode is marked with 2", the insulating plastic barrier is marked with 3", the insulating plastic tie is marked with 4", and the central angle is marked with α).

[0063] Monitoring experiment:

[0064] The current was recorded every 10 minutes by a data logger; BOD5 and COD indicators were monitored daily for bioelectrochemical inlet and outlet water samples. After Example 1, Example 2, and Example 3 reached a stable state, the current stabilized at 6.25±0.31 mA, 8.47±0.11 mA, and 17.86±0.30 mA, respectively; and the BOD5 / COD increase values ​​stabilized at 0.24±0.04, 0.28±0.02, and 0.33±0.02, respectively.

[0065] Result demonstration:

[0066] In terms of output current: The results of each embodiment show that the bioelectrochemical electrode with arc-shaped sub-electrodes has good conductivity and excellent biological retention, so that the current output of the entire system is maintained at a high level. At the same time, the current displayed by electrodes with different central angles is different. In the bioelectrochemical electrode with arc-shaped sub-electrodes, the central angles are 60° and 120°. Studies have shown that as the central angle increases, the biofilm formed by electrochemically active bacteria is less likely to be disturbed by water flow. Therefore, the current output by the electrode with this type of inferior arc configuration increases with the increase of the central angle. The electrode with a semi-arc configuration shows the best output current (17.86±0.30mA) and current density (1.78±0.03A / m2). This semi-arc configuration not only takes into account a certain biological retention, but also alleviates the problem of low electron transfer rate caused by phenomena such as sludge corruption and disintegration. Regarding the changes in BOD5 / COD between the inlet and outlet water, the results of various examples show that this bioelectrochemical electrode with arc-shaped sub-electrodes can further improve the biodegradability of difficult-to-degrade wastewater due to its good conductivity and excellent bioretention. Among them, the bioelectrochemical electrode with a semi-arc-shaped sub-electrode with a central angle of 180° in Example 3 exhibited the best BOD5 / COD improvement of 0.33±0.02, which is consistent with its high output current. In the remaining examples, the improvement value increased with the increase of the central angle.

[0067] In summary, the above experimental results show that the bioelectrochemical electrode with arc-shaped sub-electrodes has significant advantages in improving the biodegradability of difficult-to-degrade wastewater, especially the bioelectrochemical electrode with semi-arc-shaped sub-electrodes with a central angle of 180° has unexpected advantages.

[0068] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. Application of a bioelectrochemical electrode with an arc structure in a bioelectrochemical device for treating refractory wastewater, characterized in that: The bioelectrochemical electrode comprises an anode and a cathode arranged opposite to each other, and an insulating plastic separator arranged between the anode and the cathode, wherein the anode, the insulating plastic separator and the cathode are sequentially stacked and bonded; The anode and the cathode are each formed with at least two arc-shaped sub-electrodes; and the central angle of each arc-shaped sub-electrode in the anode and the cathode is independently 120°-180°; In the anode and the cathode, a straight electrode is formed between the two adjacent arc-shaped sub-electrodes; The anode and the cathode are both made of stainless steel fiber felt.

2. The use of the bioelectrochemical electrode with an arc structure according to claim 1 in a bioelectrochemical device for treating refractory wastewater, characterized in that: The anode and the cathode are parallel to each other.

3. Use of the bioelectrochemical electrode with an arc structure according to claim 1 or 2 in a bioelectrochemical device for treating refractory wastewater, characterized in that: The anode and the cathode extend in a vertical direction respectively.

4. Use of the bioelectrochemical electrode with an arc structure according to claim 1 in a bioelectrochemical device for treating refractory wastewater, characterized in that: The thickness of the insulating plastic barrier is 0.001-3 mm; The bioelectrochemical electrode further comprises a fixing member for fixing the anode, the cathode and the insulating plastic barrier relative to each other, and the fixing member is made of insulating material.

5. Use of the bioelectrochemical electrode with an arc structure according to claim 4 in a bioelectrochemical device for treating refractory wastewater, characterized in that: The fixing piece is an insulating plastic cable tie.

6. Use of the bioelectrochemical electrode with an arc structure according to claim 1 in a bioelectrochemical device for treating refractory wastewater, characterized in that: In the application, the bioelectrochemical electrode is arranged in an anaerobic reactor.

7. Use of the bioelectrochemical electrode with an arc structure according to claim 6 in a bioelectrochemical device for treating refractory wastewater, characterized in that: The anaerobic reactor is an upflow anaerobic sludge bed with a height-to-diameter ratio of 5-15:

1.

8. Use of the bioelectrochemical electrode with an arc structure according to claim 6 in a bioelectrochemical device for treating refractory wastewater, characterized in that: In the application, the bioelectrochemical electrode with an arc structure is applied to an upflow anaerobic sludge blanket to treat refractory wastewater using the following method, specifically including: (1) Pre-treating the bioelectrochemical electrode with an arc structure: first, rinse the surface impurities with deionized water, air-dry naturally, and then soak it in an acetone solution. After the electrode is air-dried, soak it in a sulfuric acid solution, and finally, rinse it with deionized water and place it in a clean place for later use; (2) constructing a bioelectrochemical system: placing the arc-shaped bioelectrochemical electrode treated in step (1) into an upflow anaerobic sludge bed, leading a lead wire with titanium wire to connect to a DC power supply, and providing a fixed resistor and a reference electrode; (3) Starting the bioelectrochemical system: inoculating anaerobic activated sludge into the upflow anaerobic sludge bed, pumping the refractory wastewater into the upflow anaerobic sludge bed using a peristaltic pump, and providing voltage with a DC power supply.

9. Use of the bioelectrochemical electrode with an arc structure according to claim 8 in a bioelectrochemical device for treating refractory wastewater, characterized in that: The sludge concentration of the anaerobic activated sludge is 2000-3000 mg / L; and / or the biodegradability of the refractory wastewater is BOD5 / COD=0.1-0.

2.

10. A bioelectrochemical electrode having an arc structure, characterized in that: The bioelectrochemical electrode comprises an anode and a cathode arranged opposite to each other, and an insulating plastic separator arranged between the anode and the cathode, wherein the anode, the insulating plastic separator and the cathode are sequentially stacked and bonded; The anode and the cathode are each formed with at least two arc-shaped sub-electrodes; and the central angle of each arc-shaped sub-electrode in the anode and the cathode is independently 120°-180°; In the anode and the cathode, a straight electrode is formed between the two adjacent arc-shaped sub-electrodes; The materials of the anode and the cathode are both stainless steel fiber felt; The anode and cathode are prepared by cutting the stainless steel fiber felt to specific requirements, then roughly shaping it with a cylindrical roller to form a stainless steel fiber felt electrode with an arc-shaped side, and finally fixing it with an insulating plastic spacer and cutting off the excess part.

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