Electrocatalytic system, electrode assembly and application applied to anaerobic biological treatment technology

Abstract

The application provides an electro-catalysis system applied to an anaerobic biological treatment technology, an electrode assembly and application. The electrode assembly comprises an electrode frame, a plurality of cathode electrode plates and a plurality of anode electrode plates. The cathode electrode plates and the anode electrode plates are fixed on the electrode frame at intervals. A plurality of electro-catalysis fillers are arranged at intervals along the height direction of the cathode electrode plates and the anode electrode plates. The electro-catalysis fillers are made of a plurality of "8" type woven products around a center rope. The "8" type woven product is made of modified carbon fiber filaments and a nylon wire framework. The electro-catalysis filler made of the modified carbon fiber filaments can guarantee the strength of the filler, greatly reduce the use amount of carbon materials, reduce the cost and have good corrosion resistance. Since the carbon fiber material has excellent specific surface area, the amount of microorganisms can be enriched, and the efficiency of electron transfer can be improved. Since the nylon wire framework is adopted for support, the form of the filler is guaranteed, and efficient operation of the electro-catalysis reaction is guaranteed.

Description

Technical Field

[0001] This application relates to an electrocatalytic reactor, and more particularly to an electrocatalytic system, electrode assembly, and application in anaerobic biological treatment technology. Background Technology

[0002] Bioelectrochemical systems (BESs), such as microbial fuel cells (MFCs) and microbial electrocatalytic systems (MECs), are a newly developed and highly innovative approach that combines biology and electrochemistry. These systems utilize bioelectrochemically active microorganisms to transfer electrons from a reducing electron donor to an electrode, where the electrons are then transferred through a closed circuit to the cathode to reduce the cathode electron acceptor. Based on this principle, BESs have already found a range of valuable applications. At the anode, BESs can remove various organic substances from water, including acetate, glucose, cellulose, plant root deposits, and sulfides; at the cathode, BESs can be used to produce hydrogen, reduce nitrates and nitrites, dehalogenate, decolorize, and reduce nitrobenzene. BESs can effectively reduce nitrobenzene to readily biodegradable aniline at the cathode, thereby improving the biodegradability of wastewater and achieving the purpose of pretreatment of nitrobenzene wastewater. Compared to purely biological, physicochemical, and electrochemical methods, bioelectrochemical systems possess the advantages of all these methods while effectively addressing some of their drawbacks. Therefore, it represents a highly promising wastewater treatment method with significant potential and development value. However, current bioelectrochemical systems typically use electrodes made of metal or graphite plates, which are prone to corrosion, have weak microbial enrichment capabilities, and suffer from high investment costs for engineering applications. Furthermore, their limited ability to break down and open rings in recalcitrant organic compounds hinders their large-scale engineering application. Summary of the Invention

[0003] This application provides an electrocatalytic system, electrode assembly, and application for anaerobic biological treatment technology to solve the problems existing in related technologies. The technical solution is as follows:

[0004] In a first aspect, embodiments of this application provide an electrode assembly, including an electrode frame, multiple cathode electrode plates and multiple anode electrode plates. The cathode electrode plates and anode electrode plates are fixed at intervals on the electrode frame. Multiple electrocatalytic fillers are spaced apart along the height direction of the cathode electrode plates and anode electrode plates. The electrocatalytic fillers are woven from multiple figure-eight woven fabrics around a central rope. The figure-eight woven fabrics are woven from modified carbon fiber filaments and nylon wire skeletons.

[0005] In one embodiment, the distance between adjacent cathode electrode plates and anode electrode plates is 5-30 cm, and the distance between adjacent electrocatalytic packing materials on the same cathode electrode plate or the same anode electrode plate is 6-20 cm.

[0006] In one embodiment, the electrode frame is made of polypropylene or stainless steel.

[0007] Secondly, embodiments of this application provide an electrocatalytic system, including a reactor tank, a power supply system, and an electrode assembly as described in any of the above. The reactor tank has an inlet area, an outlet area, and an electrode area. The electrode assembly is placed in the electrode area. The power supply system is connected to the electrode assembly and provides a stable low-voltage power supply to the electrode assembly. The power supply system is located outside the reactor tank.

[0008] In one embodiment, the power system includes a regulated power supply and a junction box. One terminal of the junction box or an air switch is connected to the regulated power supply via a copper wire, and the other terminal of the junction box or an air switch is connected to the electrocatalytic filler via a carbon fiber wire.

[0009] In one embodiment, the voltage range between the cathode electrode plate and the anode electrode plate is 0.2-2.5V, and the current range is 0.001-0.02A.

[0010] In one embodiment, the system further includes an aeration system comprising a blower, a main air inlet pipe, multiple branch air inlet pipes, and multiple sets of microporous aeration pipes. The blower is located outside the reactor tank, and the blower's outlet is connected to the air inlet of the main air inlet pipe. The multiple branch air inlet pipes are respectively connected to the main air inlet pipe, and each branch air inlet pipe is equipped with an air inlet valve. The multiple sets of microporous aeration pipes are connected to the outlets of the multiple branch air inlet pipes and are located at the bottom of the reactor tank.

[0011] In one embodiment, the inlet and outlet water zones are respectively equipped with an ORP meter, a DO meter, and a pH meter.

[0012] Thirdly, embodiments of this application provide an anaerobic biological treatment system, including an upflow anaerobic reactor or a hydrolysis acidification reactor, and an electrocatalytic system as described in any of the above. The inlet zone of the electrocatalytic system is connected to the reflux zone of the upflow anaerobic reactor or the hydrolysis acidification reactor, and the outlet zone of the electrocatalytic system is connected to the water distribution system within the upflow anaerobic reactor or the hydrolysis acidification reactor.

[0013] Fourthly, embodiments of this application provide an anaerobic biological treatment system, including a completely mixed anaerobic reactor and an electrocatalytic system as described in any of the above claims, wherein the electrocatalytic system is located at the inlet end of the completely mixed anaerobic reactor.

[0014] The advantages or beneficial effects of the above technical solutions include at least the following:

[0015] The electrode assembly is constructed from modified carbon fiber filaments and a nylon wire skeleton. Compared to electrodes made of metal or graphite plates, the electrocatalytic packing material made of modified carbon fiber filaments ensures packing strength, is less prone to breakage, significantly reduces carbon material usage, lowers costs, and offers excellent corrosion resistance. Due to the nylon wire skeleton support and the excellent specific surface area of ​​the carbon fiber material, more microorganisms can adhere, ensuring rapid electron transfer and guaranteeing efficient electrocatalytic reaction. The modified carbon fiber filaments possess an excellent specific surface area, enabling the transfer of more electrons, promoting electron transfer in microbial reactions, accelerating the decomposition, ring-opening, and degradation of organic matter, and effectively improving the removal efficiency of indicators such as COD in biological treatment technology.

[0016] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of this application will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0017] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0018] Figure 1 This is a schematic diagram of the electrode assembly.

[0019] Figure 2 This is a schematic diagram of the electrocatalytic system.

[0020] Figure 3 This is a schematic diagram of the aeration system.

[0021] Figure 4 This is a schematic diagram of an anaerobic biological treatment system;

[0022] Figure 5 This is a top-level plan view of the hydrolysis-acidification reaction system;

[0023] Figure 6 A plan view of the reflux pipe for an upflow anaerobic reaction system or a hydrolysis acidification reaction system;

[0024] Figure 7 A comparative diagram of microbial distribution in electrocatalytic reactors and anaerobic reactors;

[0025] Figure 8 Comparison of microbial distribution in a coupled electrocatalytic anaerobic reactor and a coupled electrocatalytic hydrolysis acidification reactor;

[0026] Figure 9 The graph shows the VFA / COD ratio in a pilot-scale coupled electrocatalytic hydrolysis acidification reactor.

[0027] Figure 10 This is a graph showing the COD trend in a pilot-scale coupled electrocatalytic hydrolysis acidification reactor.

[0028] Figure 11 A comparative chart of the proportions of ten microorganisms in a pilot-scale coupled electrocatalytic hydrolysis acidification reactor;

[0029] Explanation of reference numerals in the attached figures:

[0030] 1. Electrode assembly; 11. Electrode frame; 12. Cathode electrode plate; 13. Anode electrode plate; 14. Electrocatalytic packing; 2. Electrocatalytic system; 21. Reactor body; 22. Aeration system; 221. Blower; 222. Main air inlet pipe; 223. Branch air inlet pipe; 224. Microporous aeration pipe; 225. Air inlet valve; 3. Upflow anaerobic reactor; 4. Water distribution system; 5. Hydrolysis acidification reactor. Detailed Implementation

[0031] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this application. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0032] Example 1

[0033] This application provides an electrode assembly 1, including an electrode frame 11, multiple cathode electrode plates 12, and multiple anode electrode plates 13. The cathode electrode plates 12 and anode electrode plates 13 are fixed to the electrode frame 11 at intervals. An adjacent cathode electrode plate 12 and an anode electrode plate 13 form an electrode pair. Multiple electrocatalytic fillers 14 are spaced apart along the height direction of the cathode electrode plates 12 and anode electrode plates 13. The electrocatalytic fillers 14 are woven from multiple figure-eight shaped braids around a central rope. The figure-eight shaped braids are woven from modified carbon fiber filaments and a nylon wire skeleton. The spacing between adjacent cathode electrode plates 12 and anode electrode plates 13 is 5-30 cm, and the spacing between adjacent electrocatalytic fillers 14 on the same cathode electrode plate 12 or the same anode electrode plate 13 is 6-20 cm. The electrode frame 11 is made of polypropylene or stainless steel. Preferably, the stainless steel material used for the electrode frame 11 is a stainless steel anti-corrosion material, i.e., an anti-corrosion layer is coated on the surface of the stainless steel. The modified carbon fiber filaments are made of existing modified carbon fiber materials.

[0034] Because the electrocatalytic packing 14 is made of modified carbon fiber filaments and a nylon wire skeleton, the amount of carbon material used is greatly reduced compared to electrodes made of metal and graphite plates, while ensuring the strength of the packing. It is less prone to breakage, thus reducing costs. The woven electrocatalytic packing 14, due to its loose texture and numerous fibers, possesses an excellent specific surface area. Supported by the nylon wire skeleton, the packing's shape is maintained, allowing for the attachment of more microorganisms. Its microbial biofilm capacity reaches 800-1400 g / m, ensuring rapid electron transfer and efficient electrocatalytic reaction. The main body of the electrocatalytic packing 14 is made of modified carbon fiber, woven from carbon fiber, nylon filaments, and a central rope. The electrocatalytic packing 14 exhibits excellent conductivity, with a resistance of approximately 20-30 Ω per meter.

[0035] The electrocatalytic filler 14 composed of modified carbon fiber material and the electrode frame 11 made of polypropylene material have good corrosion resistance and are not easily corroded. They also have good strength while ensuring extremely low resistance, thus avoiding the phenomenon that electrodes made of graphite plates and other materials are prone to pulverization and breakage.

[0036] Example 2

[0037] The following describes this embodiment in detail with reference to Example 1:

[0038] like Figure 2 , Figure 3 As shown, this application provides an electrocatalytic system 2, including a reactor tank 21, a power supply system, and an electrode assembly 1 as described in Embodiment 1. The reactor tank 21 has an inlet area, an outlet area, and an electrode area, with the electrode assembly 1 placed in the electrode area. Preferably, multiple electrode assemblies 1 are arranged side-by-side in the electrode area.

[0039] The power supply system is connected to the electrode assembly 1, providing a stable low-voltage power supply to the electrode assembly 1. The power supply system is located outside the reactor tank 21. Furthermore, the power supply system includes multiple regulated power supplies and a junction box. One end of the junction box or an air switch is connected to the regulated power supply via a copper wire, and the other end of the junction box or an air switch is connected to and fixed to the electrocatalytic packing 14 via a carbon fiber wire.

[0040] The power supply system is responsible for providing regulated current to the electrode plates. In this application, the voltage range between the cathode electrode plate 12 and the anode electrode plate 13 is 0.2-2.5V, and the current range is 0.001-0.02A. Due to the resistance of the wires, the power supply voltage and current will be higher than the voltage and current between the electrode plates.

[0041] The electrocatalytic system 2 also includes an aeration system 22, which comprises a blower 221, a main air inlet pipe 222, multiple air inlet branch pipes 223, and multiple sets of microporous aeration pipes 224. The blower 221 is located outside the reactor tank 21, and its outlet is connected to the inlet of the main air inlet pipe 222. The multiple air inlet branch pipes 223 are each connected to the main air inlet pipe 222, and each branch pipe 223 is equipped with an air inlet valve 225 to control the opening and closing of the corresponding branch pipe. The multiple sets of microporous aeration pipes 224 are connected to the outlets of the multiple air inlet branch pipes 223 and are located at the bottom inner side of the reactor tank 21.

[0042] Preferably, multiple sets of microporous aeration pipes 224 are equidistantly arranged, with their orientation parallel or perpendicular to the electrode plate placement direction. This application, through the aeration system 22, can provide a micro-oxygen environment for the electrocatalytic system 2, thereby adjusting the overall ORP value range and preventing the ORP value from becoming too low.

[0043] The inlet and outlet water areas are equipped with ORP, DO, and pH meters, respectively. The ORP, DO, and pH meters are used to monitor the operating status of the electrocatalytic system 2. They can automatically adjust the aeration system 22 according to the ORP, pH, and DO values ​​of the inlet and outlet water, thereby controlling the overall ORP value between -150mv and -400mv.

[0044] The power system of this application provides a constant current and regulated power supply for the electrode assembly 1, providing sufficient and stable low-voltage current, which can promote the enrichment of different microorganisms on the cathode electrode plate 12 and the anode electrode plate 13, promote their growth and reproduction through electron transfer, and remove pollutants. Due to the excellent conductivity of the electrocatalytic packing 14, energy consumption is reduced.

[0045] The electrocatalytic filler 14 composed of modified carbon fiber has low resistance. In addition, carbon fiber has excellent specific surface area, which can effectively transfer more electrons, promote electron transfer in microbial reactions, accelerate the decomposition, ring opening and degradation of organic matter, and effectively improve the removal efficiency of indicators such as COD in biological treatment technology.

[0046] The carbon fiber electrocatalytic filler 14 can effectively reduce the weight of the electrode assembly 1 while ensuring the contact area, and at the same time ensure sufficient high current density under low voltage and current conditions.

[0047] Electrocatalysis technology promotes electron transfer in microorganisms by applying external voltage and current, increasing the potential difference to accelerate biological reactions, thus speeding up the fermentation and degradation of pollutants and their removal and transfer. Due to the different electron gain and loss at the cathode and anode plates 12 and 13, electrocatalysis promotes the accumulation of different microorganisms at these electrodes, fostering their rapid growth and reproduction. Under the influence of the low-voltage current, the microorganisms at both electrodes facilitate electron pair transfer in their biological reactions, transferring electrons to the reactor tank 21 via conductive microorganisms. Electrocatalysis effectively reduces the difficulty of pollutant removal and also facilitates the synergistic removal of pollutants such as C, N, and P, making it a highly efficient and low-energy-consumption biological treatment technology. The electrocatalytic process can achieve high removal rates of suspended solids and organic matter in a short time and under relatively high loads, and can decompose recalcitrant organic macromolecules into easily degradable small organic molecules, significantly improving the biodegradability and solubility of wastewater. Meanwhile, electrocatalysis technology has a certain detoxification ability, which can intercept, ferment and degrade some toxic pollutants in wastewater, effectively improving the biodegradability of wastewater.

[0048] Example 3

[0049] This embodiment will be described in detail with reference to Embodiment 2:

[0050] Currently, biological treatment methods are widely used in wastewater treatment to remove pollutants. Their advantages include low cost and excellent treatment efficiency, but their disadvantages include long cultivation and acclimatization periods and weak resistance to shocks. Early wastewater treatment technologies primarily employed aerobic biological treatment. However, with increasingly stringent discharge standards and constantly changing influent water quality, traditional aerobic biological treatment technologies have become unsuitable for the current situation. Therefore, anaerobic technology has begun to gain popularity in the wastewater treatment field. Anaerobic biological treatment technology is the process by which facultative anaerobic and anaerobic microbial communities convert organic matter into methane and carbon dioxide under anaerobic conditions; it is also known as anaerobic digestion. Anaerobic biological treatment technology has the following advantages: ① low energy consumption; ② ability to recover and reuse methane; ③ ability to handle high-concentration influent and high treatment efficiency.

[0051] However, anaerobic biological treatment technology has the following disadvantages: due to the slow growth of its microorganisms, its initial start-up time is long; it has high temperature requirements; it is sensitive to the effects of toxins; after being damaged, the recovery period is long; and the residence time is long, resulting in low reaction efficiency.

[0052] To address the aforementioned drawbacks of anaerobic biological treatment, this application provides an anaerobic biological treatment system, including an upflow anaerobic reactor or a hydrolysis acidification reactor and an electrocatalytic system 2 as described in Example 2. The influent zone of the electrocatalytic system 2 is connected to the reflux zone of the upflow anaerobic reactor or the hydrolysis acidification reactor, and the effluent zone of the electrocatalytic system 2 is connected to the water distribution system within the upflow anaerobic reactor or the hydrolysis acidification reactor.

[0053] Anaerobic biological treatment systems include upflow anaerobic reactors, hydrolysis-acidification reactors, autotrophic denitrification processes, simultaneous nitrification-denitrification processes, and anaerobic ammonia oxidation processes. The following detailed explanations will focus on upflow anaerobic reactors and hydrolysis-acidification reactors as examples:

[0054] like Figure 4 As shown, the upflow anaerobic reactor system includes an upflow anaerobic reactor 3 and an electrocatalytic system 2 as described in Example 2. The inlet zone of the electrocatalytic system 2 is connected to the reflux zone in the middle of the upflow anaerobic reactor 3, and a guide plate is provided in the inlet zone. The outlet zone of the electrocatalytic system 2 is connected to the water distribution system 4 in the upflow anaerobic reactor 3.

[0055] In this upflow anaerobic reactor system, the electrocatalytic system 2 is placed inside the upflow anaerobic reactor 3. Since the influent zone of the electrocatalytic system 2 is connected to the reflux zone in the middle of the upflow anaerobic reactor 3, wastewater from the upflow anaerobic reactor 3 is introduced into the electrocatalytic system 2 through the communicating vessel effect. Baffles are used to ensure the flow pattern of the wastewater and avoid short-circuiting and dead zones.

[0056] The electrode zone is located at the front end of the influent zone, and the effluent zone is located at the rear end of the electrode zone. Multiple sets of electrode components 1 are evenly distributed within the electrode zone. After entering the electrocatalytic system 2, wastewater is enriched by microorganisms through the electrode components 1, and pollutants are removed, chain-broken, and ring-opened under the action of a low-voltage electric field. Wastewater entering the effluent zone is pumped to the distribution system 4 by a lift pump, and then evenly distributed again within the upflow anaerobic reactor 3. The aforementioned distribution system 4 is existing technology and is sufficient to achieve uniform separation of wastewater.

[0057] In this upflow anaerobic reactor system, the influent retention time is 0.5 hours, the influent flow rate is consistent with the reflux flow rate of upflow anaerobic reactor 3, and the regulated power supply is 1.0V to 2.0V, which can be adjusted according to actual conditions. The electrocatalytic system 2 consists of six groups, each containing four electrode groups. Each electrode group comprises six pairs of electrodes, totaling twelve electrode plates. The spacing between the electrode plates is 5-15cm, and the spacing between adjacent electrocatalytic packing materials within the plates is 8-10cm.

[0058] Since the electrocatalytic system 2 is equipped with an aeration system 22, the sludge at the bottom of the electrocatalytic system 2 can be blown away by turning on the aeration at regular intervals, so that it can be returned to the upflow anaerobic reactor 3, thus preventing the sludge from fermenting and disintegrating in the electrocatalytic system 2.

[0059] After wastewater enters the electrocatalytic system 2, thanks to the low-voltage electric field in the electrode area, some slow-growing or dominant microorganisms are promoted by the electrocatalytic reaction, ensuring their dominance, such as in methanogenesis. Simultaneously, the microbial population becomes more abundant under the added benefit of the electrocatalytic reaction. The reaction potential difference can be adjusted by changing the voltage, promoting the reaction and significantly increasing the proportion of beneficial microorganisms.

[0060] Thanks to the promoting effect of electrocatalysis on microbial growth and reproduction, the system can rapidly proliferate and recover after a large-scale death of microorganisms due to shock. Simultaneously, because electrocatalysis can promote the chain breaking and removal of recalcitrant and toxic pollutants by microorganisms, this process can also effectively improve the system's shock resistance.

[0061] By combining the electrocatalytic system 2 with the upflow anaerobic reactor 3, the problems of long start-up cycles and slow microbial growth in anaerobic biological treatment technology are solved. The long recovery period after shocks to anaerobic biological treatment technology is also addressed.

[0062] like Figure 5 , Figure 6 As shown, the hydrolysis acidification reaction system includes a hydrolysis acidification reactor 5 and an electrocatalytic system 2 as described in Example 2. The inlet zone of the electrocatalytic system 2 is connected to the reflux zone in the middle of the hydrolysis acidification reactor 5, and a guide plate is provided in the inlet zone. The outlet zone of the electrocatalytic system 2 is connected to the water distribution system 4 in the hydrolysis acidification reactor 5.

[0063] In this hydrolysis acidification system, the electrocatalytic system 2 is placed inside the hydrolysis acidification reactor 5. Since the inlet zone of the electrocatalytic system 2 is connected to the reflux zone in the middle of the hydrolysis acidification reactor 5, wastewater from the hydrolysis acidification reactor 5 is introduced into the electrocatalytic system 2 through the communicating vessel effect. Baffles are used to ensure the flow pattern of the wastewater and avoid short-circuiting and dead zones.

[0064] The electrode zone is located at the front end of the influent zone, and the effluent zone is located at the rear end of the electrode zone. Multiple sets of electrode components 1 are evenly distributed within the electrode zone. After entering the electrocatalytic system 2, wastewater is enriched by microorganisms through the electrode components 1, and pollutants are removed, chain-broken, and ring-opened under the action of a low-voltage electric field. Wastewater entering the effluent zone is pumped to the distribution system 4 by a lift pump, and then evenly distributed again within the hydrolysis acidification reactor 5 through the distribution system 4. The aforementioned distribution system 4 is existing technology and is sufficient to achieve uniform separation of wastewater.

[0065] Since the electrocatalytic system 2 is equipped with an aeration system 22, the sludge at the bottom of the electrocatalytic system 2 can be blown away by turning on the aeration at regular intervals, so that it can be returned to the hydrolysis acidification reactor 5, thus preventing the sludge from fermenting and disintegrating in the electrocatalytic system 2.

[0066] like Figure 6 , Figure 7 The figure shows the microbial results of a pilot-scale test in a dyeing and printing wastewater. This pilot-scale test used an upflow anaerobic reactor 3 and a hydrolysis acidification reactor 5, both equipped with an electrocatalytic system 2. The figure shows the microbial analysis after three months of continuous influent operation. The top 30 microorganisms by percentage in the anaerobic reactor were compared. Compared to the anaerobic reactor, the content of "Other" bacteria was significantly reduced in electrocatalytic system 2, while the content of *Erysipelothrix*, *Desulfuromonas*, *unidentified_Synergistaceae*, *Soehngenia*, *Thermovirga*, and *Proteiniphilum* showed significant increases. *Proteiniphilum*, which had a low percentage in the anaerobic reactor, increased in electrocatalytic system 2, reaching the top ten in abundance. Its main function is acetic acid production. The proportions of three microorganisms—*Erysipelothrix*, *Desulfuromonas*, and *unidentified_Synergistaceae*—were significantly higher in electrocatalytic system 2 than in the upflow anaerobic reactor. *Erysipelothrix* participates in anaerobic processes and sulfur oxidation; *Desulfuromonas* is involved in sulfate and iron reduction; and *unidentified_Synergistaceae* is an symbiotic microorganism involved in acetic acid metabolism. Simultaneously, *Thermovirga*, an electroactive microorganism, was found in both reactors, accelerating hydrolysis and the production of small organic molecules. Furthermore, the methanogenesis stage is the rate-limiting stage of the anaerobic reaction, and the addition of electrocatalysis effectively increased the proportion of methanogens in the reactor; the proportion of methanogens in electrocatalytic system 2 was 26.17% higher than that in the upflow anaerobic reactor. Meanwhile, the presence of a large number of sulfate-reducing and sulfur-oxidizing bacteria in the electrocatalytic system 2 confirms the existence of the carbon-nitrogen-sulfur cycle within the reactor. The higher levels of these bacteria compared to the anaerobic reactor demonstrate that electrocatalysis has a positive promoting effect on this cycle and can facilitate its occurrence.

[0067] Compared with the microorganisms in the hydrolysis acidification reactor, it was found that the main microbial species in this reactor were quite similar. Among the top 30 abundance microorganisms, 4 microorganisms showed differences. Considering that it is a series reactor, the similar distribution of microorganisms is quite normal. The distribution of microorganisms in electrocatalytic system 2 showed significant differences. Compared with the anaerobic reactor, the hydrolysis acidification reactor, and electrocatalytic system 21, five of the top thirty abundant microorganisms were not found in the top thirty abundance of other reactors. These were Marinobacterium (related to azo dye degradation), Fontibacter (related to iron reduction), Thaurea (capable of degrading aromatic pollutants and possessing denitrification and short-cut denitrification functions), Commonas (using various short-chain organic acids and alcohols as carbon sources to synthesize PHA polymers or copolymers), and Ottowia (capable of phenol degradation and hydrolysis of macromolecular organic matter). At the same time, the proportion of bacteria related to hydrolysis function, such as Lentimicrobium (electroactive bacteria with fermentation capabilities) and Macellibacteroides (capable of degrading macromolecules such as proteins, sugars, and cellulose, thus playing a role in hydrolysis acidification), was higher than that in the hydrolysis acidification reactor. In addition, the proportion of sulfur cycle-related bacteria, such as sulfate-reducing bacteria, was also higher than that in the hydrolysis acidification reactor. This data demonstrates that the electrocatalytic system can promote the growth and reproduction of hydrolytic acidifying microorganisms and facilitate the generation of carbon, nitrogen, and sulfur cycles. Thauera has attracted considerable attention from experts and scholars, who consider it a key genus for the combination of short-cut nitrification / denitrification and anaerobic ammonia oxidation. Its presence and high proportion in this reactor also indicate that electrocatalysis can promote short-cut nitrification / denitrification.

[0068] After one month of operation, the COD removal rate reached the design value, and after two months of continuous operation, the reactor load reached the design value, confirming that electrocatalysis promotes the rapid start-up of the reactor.

[0069] This data demonstrates that electrocatalysis can accelerate anaerobic digestion and enhance the reactor's ability to break down recalcitrant organic compounds, effectively breaking down organic pollutants in water.

[0070] In this application, the carbon fiber filler on the positive and negative electrode plates does not directly participate in the reaction process. Instead, it promotes the reaction of microorganisms enriched on the positive and negative electrode plates by providing electrons and a low-voltage electric field. In an electrochemical reaction, electrons are transferred from one substance to another, generating a potential difference. The potential difference refers to the potential difference between two substances, and it is the driving force for the electrochemical reaction. If the potential difference between the two substances is positive, electrons will transfer from the substance with the lower potential to the substance with the higher potential, and vice versa. At room temperature, the larger the electrochemical potential difference, the faster the reaction rate. Therefore, the electrochemical potential difference is one of the important factors in the electrochemical reaction rate. In practical applications, we can control the rate and direction of the electrochemical reaction by adjusting the electrochemical potential difference. In this application, by applying a low-voltage electric field to the positive and negative electrode plates, the potential difference between the two electrodes is widened under the action of the low-voltage electric field, accelerating the electron transfer efficiency and thus increasing the rate of the electrochemical reaction. The reaction of microorganisms removing pollutants is itself a process of electron transfer, involving oxidation and reduction reactions, hence the terms electron donor and electron acceptor. In anaerobic systems, the lack of strong oxidizing electron acceptors (such as oxygen) is a significant limiting factor for the low degradation rate and slow metabolism of microorganisms, and electron transfer between bacteria is a major rate-limiting factor. The process of microorganisms removing contaminants is also a process of their growth and reproduction. Promoting their reactions can effectively help microorganisms grow and reproduce, especially for slow-growing microorganisms such as autotrophs. Adjusting the potential difference can assist in the enrichment of different types of microorganisms, including electroactive microorganisms such as Geobacter and Shewanella.

[0071] Taking Geobacter as an example, Geobacter possesses both discharge and absorption capabilities, exhibiting different reaction patterns at the positive and negative electrode plates. Within the electrocatalytic system 2, electrons move from the cathode to the anode. Therefore, microorganisms act as electron acceptors at the cathode, undergoing reduction reactions to reduce pollutants in wastewater. At the anode, microorganisms act as electron donors, undergoing oxidation reactions to oxidize pollutants in wastewater. For example, at the cathode, Geobacter acts as an electron donor, transferring electrons to other microorganisms or directly to pollutants, such as to methanogenic archaea. Methanogenic bacteria utilize the increased potential difference in the electrocatalytic system to rapidly convert organic pollutants in wastewater into methane or carbon dioxide, achieving anaerobic fermentation. They can also directly reduce organic pollutants in wastewater, such as through iron reduction reactions. At the anode, Geobacter acts as an electrode acceptor, directly utilizing the electrons provided by the electrode to oxidize organic matter in wastewater. It can also transfer these electrons to other microorganisms, forming aggregates. Under the expanded potential difference of the electrocatalytic system, it promotes the oxidation, decomposition, chain breaking, and fermentation of organic pollutants in wastewater. Simply put, oxidation occurs at the anode, which is an anaerobic fermentation reaction, while reduction occurs at the cathode, which is an anaerobic digestion reaction.

[0072] Taking VFA as an example: VFA is volatile fatty acid, a product of the hydrolysis and acidification stages in the four stages of anaerobic reaction, and is one of the standards for measuring the effectiveness of hydrolysis and acidification. VFA / COD is a new method for measuring the biodegradability of wastewater, in addition to the B / C ratio. The higher the VFA / COD ratio, the higher the proportion of short-chain fatty acids in the wastewater, and these short-chain fatty acids are easily utilized by microorganisms.

[0073] The results are as follows Figure 9 As shown, this pilot-scale test used high-concentration dyeing and printing wastewater as the experimental subject. Figure 9 As can be seen, the VFA / COD ratio increases significantly under the action of electrocatalysis, especially in the hydrolysis acidification reactor, where the VFA proportion is close to 50%. Meanwhile, regarding COD data, with the support of the electrocatalytic system, the COD removal rate of anaerobic tank 1 is close to 65%, and the COD removal rate of anaerobic tank 2 also reaches over 65%. This fully demonstrates the promoting effect of the electrocatalytic system on anaerobic reactions, accelerating anaerobic digestion.

[0074] like Figure 10 As shown, taking COD as an example, this pilot-scale test used low-to-medium concentration dyeing and printing wastewater as the experimental subject. Figure 10This study compares the COD treatment effects before and after the installation of the electrocatalytic system. The overall experiment began on March 17th, and the installation of the electrocatalytic system was completed on March 30th. The removal effect began to appear 9 days after installation and gradually became apparent, demonstrating that the electrocatalytic system can effectively shorten the start-up and commissioning time. After 28 days of continuous operation, the treatment effect gradually improved, the influent and effluent data stabilized, and the design load was reached after 58 days of operation. The overall start-up and commissioning period was less than two months. After the start-up and commissioning period, although there were significant fluctuations in water quality, they did not affect the overall treatment effect of the reactor, verifying the improved shock resistance of the anaerobic reactor by the electrocatalytic system.

[0075] In this pilot test, the COD removal rate of the two-stage anaerobic + hydrolysis acidification reactor reached 50%. Combined with the downstream A2O reactor, the overall COD removal rate reached 85%, and the average COD of the secondary sedimentation tank effluent was below 500 mg / L. Furthermore, after 30 days of continuous operation, the COD removal rate of the two-stage anaerobic + hydrolysis acidification reactor reached 55%, the overall COD removal rate reached 90%, and the average COD of the secondary sedimentation tank effluent was 430 mg / L.

[0076] like Figure 11 The image shows a comparative analysis of ten key microorganisms in a pilot-scale reactor for industrial wastewater treatment. These ten microorganisms are all functionally directly related to anaerobic or electrocatalytic reactions, representing characteristic microorganisms for these reactions. Geobactor, unidentified_Rikenellaceae, Lentimicrobium, and Thermovirga are electroactive microorganisms, while Methanomethylovorans is a methanogen. Geobactor and Methanomethylovorans can accelerate the anaerobic methanogenesis process under the action of the electrocatalytic system, a process that is generally rate-limiting. Furthermore, Lentimicrobium also exhibits fermentation activity, while Thermovirga accelerates hydrolysis and the production of small-molecule organic matter.

[0077] Leucobacter is an anaerobic microorganism that degrades organic pollutants; Marinobacterium is a microorganism that degrades azo dyes; Anaerovorax is an anaerobic microorganism that degrades COD; Hydrogenoanaerobacterium is an anaerobic hydrogen-producing microorganism that can supply the hydrogen it produces to hydrogen-type methanogens; Soehngenia is a hydrolytic acetic acid-producing microorganism.

[0078] As can be clearly seen from the figure, under the promoting effect of electrocatalysis, the proportion of this type of microorganism in electrocatalytic system 2 is significantly higher than that in the anaerobic reactor. The two most abundant microorganisms are Marinobacterium and Geobacter. The difficulty of this pilot test is the removal of azo dyes. The electrocatalytic system successfully promoted the growth and reproduction of Marinobacterium.

[0079] Example 4

[0080] The following describes this embodiment in detail with reference to Embodiment 2:

[0081] This application provides an anaerobic biological treatment system, including a completely mixed anaerobic reactor and an electrocatalytic system as described in Example 2, wherein the electrocatalytic system is located at the inlet end of the completely mixed anaerobic reactor.

[0082] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0083] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0084] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in this application, and these should all be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An electrode assembly, characterized in that, It includes an electrode frame, multiple cathode electrode plates and multiple anode electrode plates. The cathode electrode plates and anode electrode plates are fixed to the electrode frame at intervals. Electrocatalytic fillers are provided on both the cathode electrode plates and anode electrode plates. Multiple electrocatalytic fillers are provided at intervals along the height direction of the cathode electrode plates and anode electrode plates. The electrocatalytic fillers are made of multiple figure-eight woven fabrics woven around a central rope. The figure-eight woven fabrics are made of modified carbon fiber filaments and nylon wire skeleton.

2. The electrode assembly according to claim 1, characterized in that, The spacing between adjacent cathode and anode plates is 5-30 cm, and the spacing between adjacent electrocatalytic packing materials on the same cathode or anode plate is 6-20 cm.

3. The electrode assembly according to claim 1, characterized in that, The electrode frame is made of polypropylene or stainless steel.

4. An electrocatalytic system, characterized in that, The reactor includes a reactor body, a power supply system, and an electrode assembly as described in any one of claims 1 to 3. The reactor body has an inlet zone, an outlet zone, and an electrode zone. The electrode assembly is placed in the electrode zone. The power supply system is connected to the electrode assembly and provides a stable low-voltage power supply to the electrode assembly. The power supply system is located outside the reactor body.

5. The electrocatalytic system according to claim 4, characterized in that, The power supply system includes a regulated power supply and a junction box. One end of the junction box or an air switch is connected to the regulated power supply via a copper wire, and the other end of the junction box or an air switch is connected to the electrocatalytic filler via a carbon fiber wire.

6. The electrocatalytic system according to claim 5, characterized in that, The voltage range between the cathode electrode plate and the anode electrode plate is 0.2-2.5V, and the current range is 0.001-0.02A.

7. The electrocatalytic system according to claim 4, characterized in that, It also includes an aeration system, which includes a blower, a main air inlet pipe, multiple air inlet branch pipes, and multiple sets of microporous aeration pipes. The blower is located outside the reactor tank, and the blower's outlet is connected to the air inlet of the main air inlet pipe. The multiple air inlet branch pipes are connected to the main air inlet pipe, and each air inlet branch pipe is equipped with an air inlet valve. The multiple sets of microporous aeration pipes are connected to the air outlets of the multiple air inlet branch pipes and are located at the bottom inside the reactor tank.

8. The electrocatalytic system according to claim 4, characterized in that, The inlet and outlet water areas are equipped with ORP, DO and pH meters respectively.

9. An anaerobic biological treatment system, characterized in that, It includes an upflow anaerobic reactor or a hydrolysis acidification reactor, and an electrocatalytic system as described in any one of claims 4 to 8, wherein the inlet zone of the electrocatalytic system is connected to the reflux zone of the upflow anaerobic reactor or the hydrolysis acidification reactor, and the outlet zone of the electrocatalytic system is connected to the water distribution system within the upflow anaerobic reactor or the hydrolysis acidification reactor.

10. An anaerobic biological treatment system, characterized in that, It includes a completely mixed anaerobic reactor and an electrocatalytic system as described in any one of claims 4 to 8, wherein the electrocatalytic system is located at the inlet end of the completely mixed anaerobic reactor.

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