A method for realizing sludge reduction and water purification by coupling food chain with biofilm electrode

Abstract

The present application belongs to the field of sewage treatment and sludge reduction, and discloses a method for realizing sludge reduction and water purification by coupling biological membrane electrode with food chain. In view of the problems of poor reduction effect and incomplete water purification in traditional sludge treatment method, the present application adopts the method of coupling biological membrane electrode with food chain, adopts the strategy of constructing biological membrane electrode system and optimizing food chain structure, detects microbial community structure and water quality indexes in sludge, extracts microbial metabolic behavior on the biological membrane electrode and predatory behavior in the food chain, judges the characteristics of sludge reduction and water purification, and realizes the functions of sludge reduction and water purification in combination with sludge reduction rate and water quality threshold. Compared with the traditional technology, the present application can significantly improve the sludge reduction efficiency and water purification effect, has the characteristics of high treatment stability, and is especially suitable for practical application in the field of municipal and industrial sewage treatment.

Description

Technical Field

[0001] This invention belongs to the field of sludge reduction technology in wastewater treatment, and in particular relates to a method for achieving sludge reduction and water purification by using biofilm electrodes coupled with the food chain. Background Technology

[0002] With the acceleration of urbanization and rapid industrial development, the volume of wastewater treated is increasing daily, leading to a sharp rise in sludge production. Sludge is a byproduct of wastewater treatment, with a complex composition containing large amounts of organic matter, pathogens, heavy metals, and recalcitrant substances. If not properly treated, sludge can cause serious environmental pollution, such as emitting foul odors, spreading diseases, and contaminating soil and water sources. Furthermore, sludge treatment and disposal constitute a significant portion of the operating costs of wastewater treatment plants, accounting for approximately 30% to 60% of total operating costs. Therefore, achieving sludge reduction, harmlessness, and resource recovery has become a hot research topic and a challenging issue in the field of wastewater treatment.

[0003] Traditional sludge treatment methods include landfill, incineration, and land application. Landfill is the simplest and most commonly used method, but it has drawbacks such as consuming large amounts of land resources and polluting groundwater. Incineration can rapidly reduce the volume of sludge, but it requires a large amount of energy and produces secondary pollution, such as the emission of harmful substances like dioxins. Land application can realize the resource utilization of sludge, but it requires strict pretreatment to reduce the content of heavy metals and pathogens; otherwise, it will harm the soil and crops. Therefore, finding an efficient, environmentally friendly, and economical sludge treatment method is of significant practical importance.

[0004] In recent years, with the development of biotechnology and ecological engineering, research on sludge reduction using microorganisms and food chain principles has gradually attracted attention. Biofilm electrode technology is an emerging wastewater treatment technology that forms a biofilm on the electrode surface, utilizing the electrochemical activity of microorganisms to oxidize and decompose organic matter while generating electricity. Biofilm electrode technology has advantages such as high treatment efficiency, low energy consumption, and low sludge production. Food chain sludge reduction technology, on the other hand, constructs an artificial food chain, utilizing the predation and competition relationships between microorganisms to convert organic matter in sludge into microbial biomass, thereby achieving sludge reduction. Related patents provide practical support but still have shortcomings. For example, patent CN117326678A constructs an electrochemically enhanced multi-level food chain biofilm system, connecting a P / F-TiO2-N penetrating electrode module in series with a PA-N-rGO fiber carrier to form a stepped food chain that preys on excess sludge, resulting in sludge production only 1-30% of traditional processes; however, the synergistic mechanism between the two is not fully understood. Another patent, CN114605050A, designs a worm-microbe synergistic system that promotes symbiosis using porous packing materials, reducing TS and VS by over 21% and lowering treatment costs by 30%, but lacks long-term engineering data. Patent CN216972292U's worm bed reactor achieves an 80.6% worm recovery rate through temperature-controlled aeration, halving energy consumption, and is suitable for the retrofitting of small and medium-sized water plants. Overall, while existing technologies have made breakthroughs in technological coupling and engineering adaptability, further in-depth analysis of the synergistic mechanism and verification of stability in multiple scenarios are needed. The main shortcomings of current research in this field, both domestically and internationally, are: (1) The coupling mechanism between biofilm electrodes and the food chain is not clear enough. There is a lack of systematic theoretical research and practical verification, making it difficult to achieve efficient synergy between the two, thus limiting the further improvement of sludge reduction and water purification effects.

[0005] (2) Most existing research is still in the laboratory stage. There is a lack of effective countermeasures for complex situations in actual engineering applications, such as water quality fluctuations, temperature changes, and differences in sludge properties, resulting in poor system stability and reliability.

[0006] (3) The operating cost is high. A lot of resources and funds are needed for the selection of electrode materials, the cultivation and release of microorganisms, and the operation and maintenance of equipment, which limits the large-scale promotion and application of this technology. Summary of the Invention

[0007] This invention is made in view of the problems existing in the prior art. In traditional sludge treatment and water purification technologies, biofilm electrode technology and food chain sludge reduction technology each have certain advantages, but they have not yet achieved a deep and effective combination, and there are shortcomings in terms of treatment efficiency, stability and cost control.

[0008] To address the aforementioned issues, this invention innovatively proposes a synergistic theory of coupling biofilm electrodes with the food chain. Traditional biofilm electrode technology primarily focuses on the electrochemical oxidation and decomposition of organic matter by microorganisms on the electrode surface. This invention, however, combines this with the principles of the food chain, considering the material cycling and energy flow among microorganisms from an ecosystem perspective. For example, the electric field environment generated by the biofilm electrode affects the metabolic activity and community structure of microorganisms, thereby influencing the growth and predation relationships of organisms at each level of the food chain. By establishing a coupling model of the electric field, microorganisms, and the food chain, comprehensive regulation of sludge reduction and water purification can be achieved based on this model.

[0009] Furthermore, this invention not only introduces common microorganisms and micro-animals, but also adds sulfur-reducing bacteria with special metabolic functions, thermophilic steatobacterium, Acinetobacter with phosphorus removal function, as well as cyanobacteria with photosynthetic autotrophic function and water fleas with the ability to prey on large particulate organic matter, thus enriching the structure and function of the food chain. It employs monitoring and analysis methods such as confocal laser scanning microscopy (CLSM), metagenomics technology, and flow cytometry to accurately and in real time grasp the growth of biofilms and the dynamic changes of the food chain.

[0010] This invention overcomes the limitations of traditional single-treatment technologies by organically combining biofilm electrodes and the food chain using a systems engineering approach. By optimizing electric field parameters, food chain structure, and microbial community composition, it achieves synergistic treatment of sludge reduction and water purification. Based on sludge properties and water quality characteristics, the electric field strength and the amount of organisms at each level of the food chain are dynamically adjusted, enabling the system to adapt to different treatment conditions and improving treatment efficiency and stability.

[0011] This invention establishes a complete operation and management system. It employs an automated control system, combined with IoT technology and a big data analytics platform, to monitor and adjust operating parameters in real time. Through the analysis of long-term monitoring data, and using time series analysis methods and an ecological model based on machine learning algorithms, intelligent decision-making and optimized control of the treatment process are achieved, ensuring the stability and sustainability of sludge reduction and water purification effects.

[0012] The technical solution of the present invention: A method for achieving sludge reduction and water purification by coupling a food chain with a biofilm electrode includes the following steps: Step 1: Place the electrode in the wastewater treatment tank, connect it with copper wires to form a closed loop, and set up an external power supply. The voltage is precisely controlled between 0.5 and 2V, and the power fluctuation range is controlled within ±0.05V to provide a stable and precise electric field environment. Meanwhile, the electrode surface is inoculated with electrochemically active microorganisms. The electrodes are made of carbon felt, graphite plate, titanium mesh, stainless steel mesh, graphene-modified carbon-based composite material, or electrodes modified with nano-titanium dioxide. The electrode area is determined according to the processing scale, ranging from 0.1 to 1 m². 2 ; The microorganisms are *Geobacterium*, *Shewanella*, or *Thioretinobacterium*, with an inoculum size of 10. 7 ~10 9 The concentration of CFU / mL must be measured, and the activity of the microorganisms at the time of inoculation must be detected by flow cytometry to ensure that the activity is above 90%, so as to promote the rapid and stable formation of biofilm. Step 2: Add bacteria that can decompose organic matter to the sewage treatment pond; then introduce protozoa that feed on the bacteria; finally, introduce metazoa that feed on the protozoa to build a multi-level food chain. The bacteria are Bacillus, Pseudomonas, or Bacillus stearothermophilus, added at a concentration of 10. 6 ~10 8 CFU / mL; The protozoa are paramecia, amoebas, or tetrahymena, introduced at a density of 10. 3 ~10 5 cells / mL; The metazoans are rotifers, nematodes, or chironomid larvae, and the release density is 10. 2 ~10 4 per mL.

[0013] Multi-level food chain construction can introduce other microorganisms and micro-animals with specific functions, such as Acinetobacter spp. with phosphorus removal function, cyanobacteria with photosynthetic autotrophic function, and water fleas with the ability to prey on large particulate organic matter, according to the properties of sludge and water quality characteristics. Step 3, monitoring biofilm growth: The thickness and three-dimensional structure of the biofilm were observed every 24 hours using a confocal laser scanning microscope (CLSM); metagenomics was used to detect the gene composition and functional gene expression of microorganisms in the biofilm, and quantitative real-time PCR was used to detect the gene copy number of microorganisms; the electrochemical activity of microorganisms, such as changes in current density on the electrode surface, was measured using microelectrode technology. When the biofilm thickness reaches 100-500 μm and the number of microorganisms reaches 10... 8 ~10 10 CFU / cm 2 Furthermore, the current density on the electrode surface remains stable at 0.1~1 mA / cm². 2 When the time is right, it indicates that the biofilm is growing well; Step 4: Monitor the dynamic changes of the multi-level food chain: Collect water samples regularly and use flow cytometry combined with fluorescence labeling technology to analyze the quantity and activity of organisms at each level of the multi-level food chain. The monitoring frequency is once every 48 hours. Use metagenomics technology to analyze the gene expression profile of microorganisms to determine the species composition and metabolic state of microorganisms. Based on the monitoring results, adjust the amount of organisms at each level of the multi-level food chain in a timely manner to maintain the balance and stability of the multi-level food chain. Step 5: Analyze the effects of the electric field on biofilms and multi-level food chains: Based on the changes in biofilm growth rate and microbial metabolic activity under different electric field intensities, different voltage gradients, such as 0.5V, 1V, 1.5V, and 2V, were set up and tested respectively, with each voltage gradient experiment repeated at least three times; simultaneously, a high-speed camera combined with image processing technology was used to observe the effects of the electric field on the behavior and growth of organisms at each level of the multi-level food chain, including the electrotaxis of microorganisms and the movement trajectories of protozoa and metazoa; based on the experimental results, the response surface methodology was used to determine the optimal electric field intensity to promote the synergistic effect between the biofilm electrode and the multi-level food chain; The electric field intensity adjustment can be achieved by using a pulsed electric field with a pulse frequency of 1-10 Hz and a duty cycle of 0.1-0.5. The pulse waveform can be a square wave, sine wave, or triangular wave to further enhance the synergistic effect between the biomembrane electrode and the food chain.

[0014] Step 6, evaluate the effects of sludge reduction and water purification: Regularly test the sludge moisture content, volatile solids content, and heavy metal content every 72 hours; use thermogravimetric-differential scanning calorimetry (TG-DSC) to determine the volatile solids content and thermal stability of the sludge, and use inductively coupled plasma mass spectrometry (ICP-MS) to determine the heavy metal content in the sludge; at the same time, analyze water quality indicators, including chemical oxygen demand (COD), biochemical oxygen demand (BOD), ammonia nitrogen, total phosphorus, and total nitrogen, using standard analytical methods. When the sludge moisture content is reduced to 60%~80%, the volatile solids content is reduced by 30%~50%, the heavy metal content meets the relevant environmental protection standards, and the water quality indicators meet the relevant national emission standards, it indicates that the expected treatment effect has been achieved. Step 7: Adjust operating parameters based on the evaluation results. If the sludge reduction effect is not good, increase the electric field strength to 2-3V, extend the treatment time to 1.2-1.5 times the original, or increase the amount of bacteria, protozoa, and metazoa to 1.1-1.3 times the original. If the water purification effect is not ideal, adjust the multi-level food chain structure and increase the types or quantities of organisms with purification functions, such as increasing the amount of denitrifying bacteria with denitrification function. By continuously adjusting the operating parameters and combining the optimization strategy based on genetic algorithms, optimize the treatment process and improve treatment efficiency. Step 8: To achieve long-term stable operation of sludge reduction and water purification, a comprehensive operation and management system is established. A remote monitoring system is used to monitor the operation status of the wastewater treatment pond in real time. The wastewater treatment pond is regularly maintained and inspected, with a maintenance cycle of once a week and an inspection cycle of once a month. At the same time, the treatment effect is continuously monitored, and the operation strategy is adjusted using time series analysis based on long-term monitoring data to ensure the stability and sustainability of sludge reduction and water purification effects.

[0015] The aforementioned operation management system can employ an automated control system, combined with Internet of Things (IoT) technology and a big data analytics platform, to monitor and adjust operating parameters in real time.

[0016] The beneficial effects of this invention are: (1) By coupling the biofilm electrode with the food chain, the metabolic function of microorganisms on the biofilm electrode and the predation relationship of organisms at all levels in the food chain can be fully utilized, which can significantly improve the decomposition and conversion efficiency of sludge, reduce the sludge moisture content to 60%~80%, reduce the volatile solids content by 30%~50%, effectively reduce the volume of sludge, and greatly reduce the difficulty and cost of subsequent sludge treatment and disposal.

[0017] (2) While achieving sludge reduction, this invention also has a good water purification effect. The decomposition of organic matter by microorganisms in the food chain and the electrochemical action of the biofilm electrode can effectively remove pollutants such as chemical oxygen demand (COD), biochemical oxygen demand (BOD), ammonia nitrogen, total phosphorus, and total nitrogen from sewage, so that the water quality indicators meet the relevant national emission standards, providing a strong guarantee for the recycling of water resources and environmental protection.

[0018] (3) By adopting advanced monitoring technology and automated control system, the system can monitor biofilm growth, food chain dynamics and treatment effects in real time, and adjust operating parameters in a timely manner according to actual conditions. At the same time, the sound operation management system and intelligent decision-making mechanism ensure that the system can operate stably under different treatment conditions, improve the stability and reliability of the treatment process, and reduce the interference and impact of human factors. Attached Figure Description

[0019] Figure 1 A schematic diagram of a system structure for achieving sludge reduction and water purification by coupling a biofilm electrode to a food chain.

[0020] Figure 2 A comparison chart showing the effects of sludge reduction and water purification under different electric field intensities.

[0021] In the diagram: 1. System inlet, 2. System outlet, 3. Aeration system, 4. Oxygen bubbles, 5. Electrode, 6. Microorganisms, 7. Bacteria, 8. Protozoa, 9. Metazoa. Detailed Implementation

[0022] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0023] A method for achieving sludge reduction and water purification by coupling a food chain using biofilm electrodes is shown in the attached schematic diagram. Figure 1 As shown, the feature includes the following steps: Step 1: Select electrode materials. In addition to common carbon felt and graphite plates, graphene-modified carbon-based composite materials can also be used. The electrode area is determined according to the processing scale, ranging from 0.1 to 1 m². 2 The electrodes are placed in the wastewater treatment tank and connected to form a closed circuit using low-resistance, oxidation-resistant copper wires. An external power supply is provided, with the voltage precisely controlled between 0.5 and 2V, and the power fluctuation range controlled within ±0.05V, to provide a stable and precise electric field environment. Electrochemically active microorganisms are inoculated onto the electrode surface. In addition to *Geobacterium* and *Shewanella*, sulfur-reducing bacteria with special metabolic functions can also be introduced. The inoculation amount is 10... 7 ~10 9 The inoculation concentration should be CFU / mL, and the activity of the microorganisms must be detected by flow cytometry to ensure that the activity is above 90%, promoting rapid and stable biofilm formation. The electrode material can be replaced with other materials with good conductivity and biocompatibility, such as titanium mesh, stainless steel mesh, or electrode materials modified with nano-titanium dioxide, to improve the electrode's resistance to fouling, depending on the actual wastewater treatment requirements. Step 2: Optimize the food chain structure by adding bacteria capable of decomposing organic matter to the wastewater treatment tank. In addition to Bacillus and Pseudomonas, thermophilic steatobacterium, which has a high capacity for degrading recalcitrant organic matter, can also be added at a dosage of 10. 6 ~10 8 CFU / mL; then protozoa that feed on bacteria, including Paramecium, Amoeba, and Tetrahymena, were introduced at a density of 10. 3 ~10 5 Cells / mL; finally, metazoans that feed on protozoa are introduced, including rotifers and nematodes, as well as chironomid larvae with high predation efficiency, at a density of 10. 2 ~10 4 The number of cells / mL is used to construct a multi-level food chain. The food chain construction can be carried out by introducing other microorganisms and micro-animals with specific functions, such as Acinetobacter spp. with phosphorus removal function, cyanobacteria with photosynthetic autotrophic function, and water fleas with the ability to prey on large particulate organic matter, according to the sludge properties and water quality characteristics. Step 3: Monitor biofilm growth. Observe the biofilm thickness and three-dimensional structure using a confocal laser scanning microscope (CLSM) every 24 hours. Simultaneously, employ metagenomics to comprehensively analyze the gene composition and functional gene expression of microorganisms in the biofilm. Combine this with quantitative real-time PCR to detect the gene copy number of microorganisms. Activity detection uses microelectrode technology to measure the electrochemical activity of microorganisms, such as changes in current density on the electrode surface. When the biofilm thickness reaches 100–500 μm and the microbial population reaches 10... 8 ~10 10 CFU / cm 2 Furthermore, the current density on the electrode surface remains stable at 0.1~1 mA / cm². 2 When the time is right, it indicates that the biofilm is growing well; Step 4: Monitor the dynamic changes in the food chain, collect water samples regularly, and use flow cytometry combined with fluorescent labeling technology to analyze the quantity and activity of organisms at each level of the food chain. The monitoring frequency is once every 48 hours. Use metatranscriptomics technology to analyze the gene expression profile of microorganisms to determine the species composition and metabolic state of microorganisms. Based on the monitoring results, adjust the amount of organisms at each level of the food chain in a timely manner to maintain the balance and stability of the food chain. Step 5: Analyze the impact of the electric field on the biofilm and food chain. Based on the changes in biofilm growth rate and microbial metabolic activity under different electric field intensities, set different voltage gradients, such as 0.5V, 1V, 1.5V, and 2V, and conduct tests accordingly. Each voltage gradient experiment is repeated at least three times. Simultaneously, use a high-speed camera combined with image processing technology to observe the impact of the electric field on the behavior and growth of organisms at each level of the food chain, including the electrotaxis of microorganisms and the movement trajectories of protozoa and metazoa. Based on the experimental results, use the response surface methodology to determine the optimal electric field intensity to promote the synergistic effect between the biofilm electrode and the food chain. The electric field intensity adjustment can be achieved using a pulsed electric field with a pulse frequency of 1~10Hz and a duty cycle of 0.1~0.5. The pulse waveform can be a square wave, sine wave, or triangular wave to further enhance the synergistic effect between the biofilm electrode and the food chain.

[0024] Step 6: Evaluate the sludge reduction and water purification effects. Regularly test the sludge moisture content, volatile solids content, and heavy metal content every 72 hours. Use thermogravimetric-differential scanning calorimetry (TG-DSC) to determine the volatile solids content and thermal stability of the sludge, and inductively coupled plasma mass spectrometry (ICP-MS) to determine the heavy metal content. Simultaneously, analyze water quality indicators such as chemical oxygen demand (COD), biochemical oxygen demand (BOD), ammonia nitrogen, total phosphorus, and total nitrogen using standard analytical methods. When the sludge moisture content decreases to 60%–80%, the volatile solids content decreases by 30%–50%, the heavy metal content meets relevant environmental protection standards, and the water quality indicators meet relevant national emission standards, the expected treatment effect is achieved. Step 7: Adjust operating parameters based on the evaluation results. If the sludge reduction effect is not good, the electric field strength can be appropriately increased to 2-3V, the treatment time extended to 1.2-1.5 times the original, or the amount of microorganisms and micro-animals added can be increased to 1.1-1.3 times the original. If the water purification effect is not ideal, the food chain structure can be adjusted to increase the types or quantities of organisms with specific purification functions, such as increasing the amount of denitrifying bacteria with denitrification function. By continuously adjusting the operating parameters and combining the optimization strategy based on genetic algorithms, the treatment process can be optimized and the treatment efficiency improved. Step 8: To achieve long-term stable operation of sludge reduction and water purification, a comprehensive operation management system is established. A remote monitoring system is used to monitor the equipment's operating status in real time. Regular maintenance and repairs are performed weekly and monthly. Simultaneously, the treatment effect is continuously monitored, and operating strategies are adjusted using time series analysis based on long-term monitoring data to ensure the stability and sustainability of sludge reduction and water purification effects. This operation management system can employ an automated control system combined with IoT technology and a big data analytics platform to monitor and adjust operating parameters in real time.

[0025] Example 1 This project treats residual sludge from the secondary biological treatment of a municipal wastewater treatment plant. The sludge has an initial moisture content of 98%, a volatile solids content of 70%, and the wastewater quality contains COD of 200 mg / L, ammonia nitrogen of 30 mg / L, and total phosphorus of 5 mg / L. A volume of 5 m³ is selected. 3 The reactor is made of cylindrical carbon steel, which has good corrosion resistance and sealing properties. Carbon felt is selected as the electrode material, with an electrode area of ​​0.5 m². 2 The electrodes were evenly arranged inside the reactor, and the external power supply voltage was set to 1V. Bacillus and Pseudomonas bacteria were added to the reactor at a dosage of 10... 7To ensure uniform bacterial dispersion, the reactor was stirred at 50 rpm for 30 minutes using a stirring device with a concentration of CFU / mL. Next, protozoa such as Paramecium and Amoeba were introduced at a density of 10c. 4 The concentration was increased to 100 cells / mL, and stirring was continued for 20 minutes after introduction. Subsequently, metazoans such as rotifers and nematodes were introduced at a density of 10⁻⁶. 3 The concentration of sludge was [number] cells / mL. During the reaction, the reactor temperature was controlled at 25℃ and maintained stable using a temperature control system. The pH value was maintained between 7.0 and 7.5 using an acid-base adjuster. After 15 days of treatment, the sludge moisture content decreased to 75%, the volatile solids content decreased by 40%, and the COD in the water decreased to 50 mg / L, ammonia nitrogen decreased to 8 mg / L, and total phosphorus decreased to 1 mg / L, meeting the national Class A discharge standard. The treatment effects under different electric field conditions during the treatment of this excess sludge are shown in the attached figure. Figure 2 As shown.

[0026] Example 2 The treatment involves sludge from a wastewater treatment plant in the dyeing and printing industry. The initial moisture content of the sludge is 96%, the volatile solids content is 65%, and the wastewater quality contains 500 mg / L COD, 50 mg / L ammonia nitrogen, 8 mg / L total phosphorus, and a large amount of recalcitrant organic dyes. An 8m³ volumetric sludge treatment system is used. 3 A square concrete reactor with strong impact resistance was constructed. Graphene-modified carbon-based composite material was selected as the electrode material, with an electrode area of ​​0.8 m². 2 The electrodes are vertically arranged on both sides of the reactor, and the external power supply voltage is set to 1.5V. In addition to common bacteria such as Bacillus and Pseudomonas, sulfur-reducing bacteria with special metabolic functions are also added to the reactor at a dosage of 10... 7 Add CFU / mL, then stir at 60 rpm for 40 min to ensure thorough mixing. Introduce protozoa such as Paramecium and Amoeba at a density of 10. 4 Incubate at a density of 103 / mL and stir for 25 min. Then introduce metazoans such as rotifers and nematodes at a density of 103. 3 The concentration of microorganisms in the reactor was controlled at 30℃ and the pH value was maintained between 6.5 and 7.2 during the reaction. Due to the high content of recalcitrant substances in the dyeing and printing sludge, intermittent aeration was adopted, with a 1-hour pause after every 2 hours of aeration to enhance the microbial capacity to decompose these substances. After 20 days of treatment, the sludge moisture content decreased to 70%, volatile solids content decreased by 45%, and COD in the wastewater decreased to 100 mg / L, ammonia nitrogen decreased to 15 mg / L, and total phosphorus decreased to 2 mg / L, meeting the national standards for dyeing and printing wastewater discharge.

[0027] Example 3 This treatment is for sludge from a food processing industrial wastewater treatment plant. The initial moisture content of the sludge is 97%, the volatile solids content is 75%, and the wastewater quality contains 300 mg / L COD, 20 mg / L ammonia nitrogen, and 3 mg / L total phosphorus. The sludge contains a large amount of organic matter, such as proteins and carbohydrates. The usable volume is 6 m³. 3 The reactor is made of circular fiberglass, which is lightweight and corrosion-resistant. Graphite plates were chosen as the electrode material, with an electrode area of ​​0.6 m². 2 The electrodes were placed horizontally at the bottom of the reactor, and the external power supply voltage was set to 1.2V. Bacillus and Pseudomonas bacteria were added to the reactor at a dosage of 10... 8 CFU / mL, stirred at 40 rpm for 35 min. Protozoa such as Paramecium and Amoeba were introduced at a density of 10-1. 5 Incubate at a density of 10⁶ cells / mL and stir for 20 minutes. Then introduce metazoans such as rotifers and nematodes at a density of 10⁶ cells / mL. 3 The reactor temperature was controlled at 28℃ and the pH value maintained between 7.2 and 7.8 during the reaction. Continuous micro-aeration was used to promote the decomposition of organic matter by microorganisms, with an aeration intensity of 0.5 m³ / mL. 3 / (m 2 After 12 days of treatment, the sludge moisture content decreased to 78%, the volatile solids content decreased by 35%, the COD in the water decreased to 60 mg / L, the ammonia nitrogen decreased to 5 mg / L, and the total phosphorus decreased to 0.5 mg / L, meeting the national secondary discharge standard.

[0028] Example 4 This treatment addresses sludge from a pharmaceutical wastewater treatment plant. The sludge initially has a moisture content of 95%, a volatile solids content of 60%, and the wastewater contains 800 mg / L COD, 60 mg / L ammonia nitrogen, and 10 mg / L total phosphorus, as well as significant amounts of antibiotic and drug residues. A 10m³ volumetric sludge treatment system is used. 3 The rectangular stainless steel reactor is characterized by high strength and excellent sealing. Nano-titanium dioxide-modified electrode material is used, with an electrode area of ​​1 m². 2 The electrodes are arranged in an alternating pattern inside the reactor, and the external power supply voltage is set to 2V. Drug-resistant thermophilic Bacillus stearothermophilus and Tetrahymena are added to the reactor at amounts of 10... 7 CFU / mL and 10 4 The sample was stirred at 70 rpm for 50 minutes to ensure uniform distribution. Protozoa such as Paramecium and Amoeba were introduced at a density of 10-1. 4 Incubate at a density of 103 / mL and stir for 30 min. Then introduce metazoans such as rotifers and nematodes at a density of 103. 3The concentration of microorganisms in the reactor was controlled at 32℃ and the pH value was maintained between 6.8 and 7.5 during the reaction. Because antibiotics and drug residues in pharmaceutical sludge have an inhibitory effect on microorganisms, a segmented power supply method was adopted, with a 1-hour shutdown after every 3 hours of power supply to mitigate the inhibitory effect. After 25 days of treatment, the sludge moisture content decreased to 65%, the volatile solids content decreased by 45%, and the COD in the wastewater decreased to 150 mg / L, ammonia nitrogen decreased to 20 mg / L, and total phosphorus decreased to 2 mg / L, meeting the national pharmaceutical wastewater discharge standards.

[0029] Example 5 The treatment involves sludge from a livestock wastewater treatment plant. The initial moisture content of the sludge is 99%, the volatile solids content is 80%, and the wastewater quality contains COD of 400 mg / L, ammonia nitrogen of 80 mg / L, and total phosphorus of 15 mg / L. The sludge also contains a large amount of livestock and poultry manure and microorganisms. A volume of 4 m³ is selected. 3 A cylindrical plastic reactor was developed, which is low-cost and easy to install. Carbon felt was chosen as the electrode material, with an electrode area of ​​0.3 m². 2 Electrodes are wound around the inner wall of the reactor, and the external power supply voltage is set to 0.8V. Acinetobacter spp., which has phosphorus removal capabilities, and bacteria with nitrification and denitrification capabilities are added to the reactor at a dosage of 10... 8 CFU / mL, stirred at 55 rpm for 35 min. Protozoa such as Paramecium and Amoeba were introduced at a density of 10-1. 5 Incubate at a density of 103 / mL and stir for 22 min. Then introduce metazoans such as rotifers and nematodes at a density of 103. 3 The concentration of wastewater was controlled at 22℃ and the pH value was maintained between 7.3 and 7.9 during the reaction. To improve the removal efficiency of ammonia nitrogen and total phosphorus, a circulating reflux method was adopted, in which part of the treated water was returned to the inlet at a reflux ratio of 1:2. After 18 days of treatment, the sludge moisture content decreased to 80%, the volatile solids content decreased by 30%, and the COD in the water decreased to 80 mg / L, ammonia nitrogen decreased to 15 mg / L, and total phosphorus decreased to 3 mg / L, meeting the national standards for livestock and poultry breeding wastewater discharge.

[0030] The specific embodiments described above are only used to illustrate the spirit of the present invention. The scope of protection of the present invention is not limited thereto. For those skilled in the art, other embodiments can be easily made by means of changes, substitutions or modifications based on the technical content disclosed in this specification. All such other embodiments should be covered within the scope of protection of the present invention.

Claims

1. A method for achieving sludge reduction and water purification by coupling a food chain with a biofilm electrode, characterized in that, Includes the following steps: Step 1: Place the electrode in the sewage treatment tank, connect it with copper wires to form a closed circuit, and set up an external power supply; wherein, the electrode surface is inoculated with electrochemically active microorganisms; Step 2: Add bacteria that can decompose organic matter to the sewage treatment pond; then introduce protozoa that feed on the bacteria; finally, introduce metazoa that feed on the protozoa to build a multi-level food chain. Step 3, monitoring biofilm growth: The thickness and three-dimensional structure of the biofilm are observed periodically using a confocal laser scanning microscope; metagenomics technology is used to detect the gene composition and functional gene expression of microorganisms in the biofilm, and the gene copy number of microorganisms is detected by real-time quantitative PCR; the electrochemical activity of microorganisms is measured using microelectrode technology. When the biofilm thickness reaches 100-500 μm and the number of microorganisms reaches 10... 8 ~10 10 CFU / cm 2 Furthermore, the current density on the electrode surface remains stable at 0.1~1 mA / cm². 2 When the time is right, it indicates that the biofilm is growing well; Step 4: Monitor the dynamic changes of the multi-level food chain: Collect water samples regularly and use flow cytometry combined with fluorescence labeling technology to analyze the quantity and activity of organisms at each level of the multi-level food chain; use metatranscriptomics technology to analyze the gene expression profile of microorganisms to determine the species composition and metabolic state of microorganisms; based on the monitoring results, adjust the amount of organisms at each level of the multi-level food chain in a timely manner to maintain the balance and stability of the multi-level food chain. Step 5: Analyze the effects of the electric field on biofilms and multi-level food chains: Based on the changes in biofilm growth rate and microbial metabolic activity under different electric field intensities, different voltage gradients were set and tests were conducted. Simultaneously, a high-speed camera combined with image processing technology was used to observe the effects of the electric field on the behavior and growth of organisms at each level of the multi-level food chain, including the electrotaxis of microorganisms and the movement trajectories of protozoa and metazoa. Based on the experimental results, the optimal electric field intensity was determined using the response surface methodology to promote the synergistic effect between the biofilm electrode and the multi-level food chain. Step 6, evaluate the effects of sludge reduction and water purification: regularly test the moisture content, volatile solids content, and heavy metal content of the sludge; use thermogravimetric-differential scanning calorimetry to determine the volatile solids content and thermal stability of the sludge, and use inductively coupled plasma mass spectrometry to determine the heavy metal content in the sludge; at the same time, analyze water quality indicators, including chemical oxygen demand, biochemical oxygen demand, ammonia nitrogen, total phosphorus, and total nitrogen, using standard analytical methods. When the sludge moisture content is reduced to 60%~80%, the volatile solids content is reduced by 30%~50%, the heavy metal content meets the relevant environmental protection standards, and the water quality indicators meet the relevant national emission standards, it indicates that the expected treatment effect has been achieved. Step 7: Adjust operating parameters based on the evaluation results. If the sludge reduction effect is not good, increase the electric field strength to 2-3V, extend the treatment time to 1.2-1.5 times the original, or increase the amount of bacteria, protozoa, and metazoa to 1.1-1.3 times the original. If the water purification effect is not ideal, adjust the multi-level food chain structure and increase the types or number of organisms with purification functions. By continuously adjusting the operating parameters and combining the optimization strategy based on genetic algorithms, optimize the treatment process and improve treatment efficiency. Step 8: Achieve long-term stable operation of sludge reduction and water purification, and establish a sound operation and management system; adopt a remote monitoring system to monitor the operation status of the sewage treatment pond in real time, and regularly maintain and repair the sewage treatment pond; at the same time, continuously monitor the treatment effect, and adjust the operation strategy based on long-term monitoring data using time series analysis methods to ensure the stability and sustainability of sludge reduction and water purification effects.

2. The method for achieving sludge reduction and water purification by coupling a food chain using a biofilm electrode according to claim 1, characterized in that, The electrodes are made of carbon felt, graphite plate, titanium mesh, stainless steel mesh, graphene-modified carbon-based composite material, or electrodes modified with nano-titanium dioxide.

3. The method for achieving sludge reduction and water purification by coupling a food chain using a biofilm electrode according to claim 1, characterized in that, The microorganisms mentioned are *Geobacterium*, *Shewanella*, or *Thioretinobacterium*, and the inoculum size is 10. 7 ~10 9 CFU / mL.

4. The method for achieving sludge reduction and water purification by coupling a food chain using a biofilm electrode according to claim 1, characterized in that, In step 2, The bacteria mentioned are Bacillus, Pseudomonas, or Bacillus stearothermophilus, and the addition amount is 10. 6 ~10 8 CFU / mL; The protozoa mentioned are paramecia, amoebas, or tetrahymena, introduced at a density of 10. 3 ~10 5 cells / mL; The metazoans mentioned are rotifers, nematodes, or chironomid larvae, and the release density is 10. 2 ~10 4 per mL.

5. The method for achieving sludge reduction and water purification by coupling a food chain using a biofilm electrode according to claim 1, characterized in that, The construction of a multi-level food chain involves introducing Acinetobacter spp. with phosphorus removal function, cyanobacteria with photosynthetic autotrophic function, and water fleas with the ability to prey on large particulate organic matter, based on the properties of sludge and water quality characteristics.

6. The method for achieving sludge reduction and water purification by coupling a food chain using a biofilm electrode according to claim 1, characterized in that, The electric field strength is adjusted by using a pulsed electric field with a pulse frequency of 1~10Hz and a duty cycle of 0.1~0.

5. The waveform of the pulse can be a square wave, a sine wave, or a triangular wave.

7. The method for achieving sludge reduction and water purification by coupling a food chain using a biofilm electrode according to claim 1, characterized in that, The aforementioned operation management system employs an automated control system, combined with IoT technology and a big data analytics platform, to monitor and adjust operating parameters in real time.

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