UASB wastewater treatment method

Abstract

The invention discloses a UASB (Upflow Anaerobic Sludge Blanket) wastewater treatment method. The method comprises the following steps: wastewater pretreatment; treating with a multi-stage UASB reactor; performing electrochemical oxidation treatment; product collection and biogas recovery; and post-treating the wastewater. Through the multi-stage UASB reactor system, the wastewater treatment efficiency and the biogas yield can be remarkably improved, and each stage of reactor runs under different operation conditions to adapt to the characteristic change of the wastewater, so that the problem of load fluctuation when a single-stage reactor is used for treating the high-concentration organic wastewater can be effectively solved; the stability and the impact resistance of the system are enhanced; before wastewater enters the first-stage UASB reactor, a heat exchanger is used for preheating the wastewater so as to improve the activity and degradation efficiency of anaerobic microorganisms and ensure the reaction effect, meanwhile, a plurality of reaction sections are arranged in the first-stage UASB reactor, each section has different sludge concentration and flow velocity, gradient flow is formed, degradation of different organic matters is promoted, and the wastewater treatment effect is improved. The wastewater treatment effect is further ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and specifically to a UASB wastewater treatment method. Background Art

[0002] The UASB (Upflow Anaerobic Sludge Bed) wastewater treatment method is mainly based on the principle of anaerobic digestion and has been widely used in the field of sewage treatment. Traditional sewage treatment methods, such as the activated sludge method and aerobic biological treatment, usually require a large space and high energy consumption. Anaerobic treatment, on the other hand, uses anaerobic microorganisms to degrade organic matter in an anaerobic environment, with advantages such as energy recovery, small footprint, and low operating cost. The existing UASB technology constructs an upflow reactor that allows sewage to enter from the bottom, flow through the activated sludge bed, and promote the degradation of organic matter and the generation of biogas. This technology performs excellently in treating high-concentration organic wastewater, especially in applications in industries such as agriculture, food processing, winemaking, and papermaking, achieving good operating results. Although the UASB technology has many advantages, there are still some limitations.

[0003] However, there are still significant deficiencies in the existing technology, such as: When traditional UASB (Upflow Anaerobic Sludge Bed) technology treats high-concentration organic wastewater, it often faces problems such as low degradation rate and insufficient removal rate, especially the poor treatment effect on refractory organic matter. At the same time, many industrial wastewaters contain organic matter and pollutants that are difficult to biodegrade, and these substances are often unable to be effectively removed in traditional treatment processes. Summary of the Invention

[0004] The purpose of the present invention is to provide a UASB wastewater treatment method to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solution: The UASB wastewater treatment method includes the following steps: Wastewater pretreatment; Treatment by a multi-stage UASB reactor; Electrochemical oxidation treatment; Product collection and biogas recovery; Wastewater post-treatment.

[0006] Preferably, the wastewater pretreatment specifically includes: Collecting wastewater: Collecting high-concentration organic wastewater and using a raw material pump to transport the wastewater to the pretreatment tank; Physical screening: Installing a grille at the inlet of the pretreatment tank to remove large particulate matter in the wastewater, and setting a grit chamber in the pretreatment tank to maintain a grit retention time of 30 minutes to remove sediments; pH Adjustment: Use a pH meter to detect the pH value of the wastewater. If the pH value is lower than 6.5, add lime water to increase it; if it is higher than 7.5, add dilute sulfuric acid to decrease it, ensuring that the pH before entering the UASB reactor is between 6.5 and 7.5.

[0007] Preferably, the treatment by the multi-stage UASB reactor specifically includes: Enter the first-stage UASB reactor: Transport the pretreated wastewater to the first-stage UASB reactor through a pipeline, set the flow rate to 0.5 - 1 m / h, ensure that a mixing device is set in the reactor to ensure full contact between the sewage and the sludge, set the residence time of the reactor to 12 - 24 hours, continuously monitor the COD removal rate, and enter the next stage when it reaches over 60%; Sludge circulation: Install a sludge reflux pump at the bottom of the first-stage UASB reactor, regularly reflux the precipitated activated sludge to the top of the reactor, and set the reflux ratio to 30% - 50% to improve the degradation efficiency of the activated sludge; Gas collection: Install a gas collection device at the top of the first-stage reactor to ensure that the generated biogas can be collected, regularly monitor the gas composition and production to ensure effective anaerobic reaction; Enter the second-stage UASB reactor: Introduce the wastewater treated by the first-stage UASB reactor into the second-stage UASB reactor through the bottom pipeline, keep the flow rate at 0.5 m / h, set the residence time to 12 hours, and further remove the undegraded organic matter; Continue sludge reflux: Similarly set a sludge reflux mechanism in the second-stage UASB reactor, regularly reflux the precipitated sludge to the first-stage UASB reactor, monitor the sludge reflux amount, and ensure that the sludge concentration in the reactor is between 0.5 and 2 g / L.

[0008] Preferably, before the wastewater enters the first-stage UASB reactor, use a heat exchanger to preheat the wastewater to 30 - 35 °C to improve the activity and degradation efficiency of anaerobic microorganisms.

[0009] Preferably, set multiple reaction sections in the first-stage UASB reactor, each section having different sludge concentrations and flow rates to form a gradient flow, promoting the degradation of different organic matters. Each section is provided with an independent sludge reflux system to adjust the reflux ratio of each section to adapt to different reaction conditions.

[0010] Preferably, add a biological additive in the first-stage UASB reactor to improve the degradation ability and sedimentation of the sludge, and adjust the addition amount by regularly monitoring the sludge activity.

[0011] Preferably, the electro-chemical oxidation treatment specifically includes: Enter the electrochemical oxidation unit: The wastewater treated by the second-stage UASB reactor is transported to the electrochemical oxidation unit through a pipeline. Stainless steel electrodes are installed in the electrochemical oxidation unit to ensure that the electrode spacing is 5-10 cm to optimize the current density; Fill the electrolytic cell with water: Inject the wastewater treated by UASB into the electrolytic cell to ensure that the water level reaches the minimum immersion depth of the electrodes; Apply current: Turn on the power supply, set the direct current to 20-50 mA / cm², ensure uniform current distribution, monitor the voltage and current in the electrolytic cell to ensure their stability, avoid overload, conduct the electrolysis reaction for 2-4 hours, take samples every 30 minutes for water quality analysis, and ensure that the removal rate of organic matter reaches more than 70%.

[0012] Preferably, the product collection and biogas recovery specifically include: Wastewater discharge and monitoring: After the electrochemistry reaction ends, discharge the treated wastewater from the electrolytic cell, conduct water quality monitoring, and after confirming that the water quality meets the standards, then discharge it; Biogas collection: Regularly collect biogas from the gas collection device at the top of the UASB reactor, monitor the gas composition, and use a gas purification device to remove impurities and moisture to ensure that the calorific value of the biogas meets the usage requirements.

[0013] Preferably, the post-treatment of wastewater and resource recovery specifically include: For the pollutants still remaining after electrochemical treatment, set up an aerobic treatment unit for further treatment. Turn on the aerobic reactor, set the influent flow rate and the concentration of cultivated sludge, introduce the purified biogas into the generator set for energy conversion, and the treated wastewater can be further used for irrigation and reuse.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. Through the multi-stage UASB reactor system, the treatment efficiency of wastewater and the biogas production can be significantly improved. Each stage of the reactor operates under different operating conditions to adapt to the changes in the characteristics of the wastewater. The wastewater initially degraded by the upper-stage reactor generates anaerobic sludge, which enters the lower-stage reactor by gravity or pumping to further degrade the undegraded organic matter. Each stage of the reactor can be designed to operate at different temperatures and residence times, thereby optimizing the growth environment of anaerobic microorganisms and enhancing the treatment effect. This solution can effectively solve the problem of load fluctuation when a single-stage reactor treats high-concentration organic wastewater, and enhance the stability and shock resistance of the system; 2. Before the wastewater enters the first-stage UASB reactor, a heat exchanger is used to preheat the wastewater to improve the activity and degradation efficiency of anaerobic microorganisms, ensure the reaction effect. At the same time, multiple reaction sections are set in the first-stage UASB reactor, each section having different sludge concentrations and flow rates, forming a gradient flow to promote the degradation of different organic substances and further ensure the treatment effect of the wastewater. 3. In this system, the wastewater first enters the UASB reactor for anaerobic treatment to generate biogas. Subsequently, the undegraded organic substances and nitrogen and phosphorus elements can be treated through the electro-chemical oxidation unit, and are converted into a more easily treatable form or directly removed by using the electrochemical reaction. This method not only improves the removal rate of refractory organic substances, but also reduces the burden of subsequent aerobic treatment and improves the overall energy recovery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of the overall process of the present invention; Figure 2 is a detailed flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] Please refer to Figure 1-2 , the present invention provides a technical solution: The UASB wastewater treatment method includes the following steps: Wastewater pretreatment; Collecting wastewater: collecting high-concentration organic wastewater, and using a raw material pump to transport the wastewater to a pretreatment tank; Physical screening: Install a grille at the inlet of the pretreatment tank to remove large particulate matter in the wastewater. A grit chamber is set in the pretreatment tank, and the grit retention time is maintained for 30 minutes to remove sediments; pH adjustment: Use a pH meter to detect the pH value of the wastewater. If the pH value is lower than 6.5, add lime water to increase it. If it is higher than 7.5, add dilute sulfuric acid to decrease it to ensure that the pH before entering the UASB reactor is between 6.5 and 7.5.

[0018] Use a raw material pump to transport the high-concentration organic wastewater to the pretreatment tank, ensuring that the flow rate and pressure of the pump are suitable for the physical properties of the wastewater to avoid the occurrence of bubbles or solid precipitation during the transportation process. Install a grille at the inlet of the pretreatment tank, and the aperture of the grille should be designed to effectively remove large particulate matter (such as branches, plastics, etc.) to prevent damage to subsequent equipment. There is a grit chamber in the pretreatment tank, maintaining a grit removal time of 30 minutes. Utilize the gravitational force to make the heavier solids settle, and regularly discharge the sediment to keep the grit chamber clean. Use a high-precision pH meter to continuously detect the pH value of the wastewater. If the pH value is lower than 6.5, gradually add lime water to avoid a sharp increase in pH caused by excessive addition; if it is higher than 7.5, slowly add dilute sulfuric acid to reduce it until the pH stabilizes between 6.5 - 7.5 to ensure that the wastewater entering the UASB reactor is treated in a suitable environment; Physical screening and grit removal treatment remove large particulate matter, reducing the burden on the subsequent reactor and improving the efficiency and stability of the reactor. pH adjustment ensures the activity of microorganisms under the optimal pH conditions, enhancing the degradation efficiency of the sewage. Through pretreatment, the treatment capacity of the subsequent UASB reactor can be significantly improved, resulting in an increase in the operating efficiency of the overall treatment system, an extension of the equipment service life, and a reduction in the failure rate.

[0019] Multi-stage UASB reactor treatment; Enter the first-stage UASB reactor: Transport the pretreated wastewater to the first-stage UASB reactor through a pipeline, with the flow rate set at 0.5 - 1 m / h. Ensure that a mixing device is installed inside the reactor to guarantee sufficient contact between the sewage and the sludge. Set the residence time of the reactor at 12 - 24 hours, and continuously monitor the COD removal rate. When it reaches over 60%, it can enter the next stage; Transport the pretreated wastewater to the first-stage UASB reactor through a pipeline, with the flow rate set at 0.5 - 1 m / h. According to the reactor design, ensure that the fluid can be evenly distributed to avoid the formation of dead zones. Install a mixing device such as a gas stirrer or a mechanical stirrer to ensure sufficient contact between the sewage and the sludge and improve the reaction efficiency.

[0020] Sludge circulation: Install a sludge reflux pump at the bottom of the first-stage UASB reactor to regularly reflux the precipitated activated sludge to the top of the reactor, with the reflux ratio set at 30% - 50% to improve the degradation efficiency of the activated sludge; Install a sludge reflux pump at the bottom of the first-stage UASB reactor to regularly reflux the deposited activated sludge to the top of the reactor. The reflux ratio is set at 30% - 50%, and this ratio needs to be adjusted according to the sludge load and organic matter concentration of the wastewater to ensure that the sludge concentration in the reactor is within the optimal range; Gas collection: Install a gas collection device at the top of the first-stage reactor to ensure that the generated biogas can be collected. Regularly monitor the gas composition and output to ensure effective anaerobic reactions. Install a gas collection device at the top of the first-stage reactor. Regularly monitor gas components such as CH4, CO2, etc. and the output to ensure the efficiency of biogas production, and timely treat possible impurities in the gas. Enter the second-stage UASB reactor: Introduce the wastewater treated by the first-stage UASB reactor into the second-stage UASB reactor through the bottom pipeline. Keep the flow rate at 0.5 m / h and set the residence time to 12 hours to further remove undegraded organic matter. Continue sludge reflux: Also set up a sludge reflux mechanism in the second-stage UASB reactor. Regularly reflux the precipitated sludge to the first-stage UASB reactor and monitor the sludge reflux volume to ensure that the sludge concentration in the reactor is between 0.5 - 2 g / L.

[0021] Set up a sludge reflux mechanism in the second-stage reactor. Timely reflux the precipitated sludge to the first-stage reactor to maintain an appropriate microbial concentration and treatment effect. Monitor the sludge reflux volume to ensure that the sludge concentration is between 0.5 - 2 g / L. Before the wastewater enters the first-stage UASB reactor, use a heat exchanger to preheat the wastewater to 30 - 35°C to improve the activity and degradation efficiency of anaerobic microorganisms.

[0022] Before the wastewater enters the first-stage UASB reactor, use a heat exchanger to preheat the wastewater to 30 - 35°C. This process can be achieved by heat exchange between hot water or steam and the wastewater to ensure that the wastewater reaches the appropriate temperature range. Temperature is a key factor affecting the metabolism of anaerobic microorganisms. By preheating, the activity of microorganisms can be significantly improved, thereby increasing the degradation efficiency of organic matter. Increasing the temperature can accelerate the rate of biochemical reactions, thus improving the overall efficiency of wastewater treatment, reducing the reaction time. In traditional UASB reactors, the preheating treatment of wastewater is often not considered, which may lead to insufficient microbial activity and affect the treatment effect. By preheating, faster reaction response and higher COD removal rate can be achieved. The preheating process and the setting of multi-stage reaction sections not only improve the treatment capacity of the UASB reactor but also create good influent conditions for subsequent treatment units such as electrochemical oxidation, making the overall treatment process more efficient.

[0023] Set up multiple reaction sections in the first-stage UASB reactor. Each section has different sludge concentrations and flow rates to form a gradient flow to promote the degradation of different organic matters. Each section is equipped with an independent sludge reflux system to adjust the reflux ratio of each section to adapt to different reaction conditions.

[0024] An independent sludge return system is set for each stage, so that the sludge return ratio of each stage can be adjusted according to the reaction conditions of different stages to meet the degradation requirements of different organic matters. By setting different flow rates and sludge concentrations in different stages, efficient degradation of different types of organic matters can be achieved. A higher sludge concentration can enhance the degradation ability of microorganisms, while an appropriate flow rate can ensure effective contact of the fluid in each stage. The independent sludge return system enables each reaction stage to be optimized according to the specific situation of the influent water, flexibly adjusted, improving the adaptability and stability of the system. Traditional UASB reactors are usually designed with a single stage, resulting in low treatment efficiency. Through the design of multiple reaction stages, organic matters with different characteristics can be effectively treated, avoiding the inefficiency caused by mismatched reaction conditions. The design of multiple reaction stages enables each stage to be optimized for treating specific types of organic matters, thereby improving the overall COD removal efficiency and ensuring that the effluent quality meets higher standards.

[0025] Appropriately add biological aids to the first-stage UASB reactor to improve the degradation ability and sedimentation property of the sludge, and adjust the addition amount by regularly monitoring the sludge activity.

[0026] According to the wastewater characteristics and microbial community, select suitable biological aids such as enzyme preparations, microbial culture media, nutrient supplements, etc. Add biological aids in appropriate amounts according to the state of the sludge in the reactor, usually measured by dry weight or volume ratio. Evaluate the effect of biological aids by regularly monitoring the sedimentation property, activity indices such as SVI, SV30, etc. of the sludge and the COD removal rate. Adjust the addition amount of biological aids in a timely manner according to the monitoring results to achieve the best treatment effect. Biological aids can promote the growth and reproduction of microorganisms and improve their metabolic activity. In this way, organic matters in the sewage can be degraded more effectively, thereby increasing the COD removal rate. Some biological aids can enhance the sludge flocculation performance, reduce suspended substances, improve sedimentation property, reduce the sludge concentration, and reduce the burden of subsequent treatment. Traditional UASB reactors usually rely on the naturally selected microbial community for degradation, which may lead to unstable treatment efficiency. Adding biological aids can optimize and enhance the microbial community, thereby improving the treatment effect. By enhancing the degradation ability of the sludge, the treated water quality is significantly improved, the COD removal rate is increased, providing better influent water for the subsequent electrochemically oxidation process. Electrochemical oxidation treatment; Enter the electrochemical oxidation unit: The wastewater treated by the second-stage UASB reactor is transported to the electrochemical oxidation unit through a pipeline. Install stainless steel electrodes in the electrochemical oxidation unit to ensure that the electrode spacing is 5 - 10 cm to optimize the current density. The wastewater treated by the second-stage UASB reactor is transported to the electro-chemical oxidation unit through pipelines. Ensure that the pipelines have an appropriate slope to prevent sewage from settling or clogging during transportation. In the electro-chemical oxidation unit, install stainless steel electrodes with an electrode spacing of 5 - 10 cm, which can optimize the current density and increase the effective surface area of the reaction. Filling the electrolytic cell with water: Inject the wastewater treated by UASB into the electrolytic cell to ensure that the water level reaches the minimum immersion depth of the electrodes. Inject the wastewater treated by UASB into the electrolytic cell to ensure that the water level reaches the minimum immersion depth of the electrodes, so as to ensure that the electrodes work effectively during the reaction and avoid the influence of bubbles or solid precipitation on the activity of the electrodes.

[0027] Applying current: Turn on the power supply, set the DC current to 20 - 50 mA / cm², ensure uniform current distribution, monitor the voltage and current in the electrolytic cell to ensure their stability and avoid overload. Conduct the electrolysis reaction for 2 - 4 hours, and take water samples for water quality analysis every 30 minutes to ensure that the removal rate of organic matter reaches over 70%.

[0028] Turn on the power supply and set the DC current to 20 - 50 mA / cm². Ensure that the current is within the recommended range to optimize the electrolysis process. Use high-precision current and voltage monitoring equipment to regularly check the voltage and current in the electrolytic cell to ensure their stability and avoid equipment damage caused by overload. The combination of electro-chemical oxidation and the UASB reactor forms a more efficient treatment process, which can effectively address the challenges of high-concentration organic wastewater, improve the overall effluent quality. Through optimizing the electrode design and current application, electro-chemical oxidation can effectively remove refractory organic matter and achieve a COD removal rate of over 70%, thus ensuring good effluent quality. By reasonably setting the current density and optimizing the electrode spacing, the energy consumption required for unit COD removal can be reduced, improving the economy of the system. This step effectively improves the quality of the wastewater treated by the UASB reactor, provides high-quality influent for subsequent treatment processes, and further enhances the treatment efficiency of the entire system.

[0029] Product collection and biogas recovery; Wastewater discharge and monitoring: After the electro-chemical reaction is completed, discharge the treated wastewater from the electrolytic cell and conduct water quality monitoring. After confirming that the water quality meets the standards, then discharge it. Biogas collection: Regularly collect biogas from the gas collection device at the top of the UASB reactor, monitor the gas composition, and use a gas purification device to remove impurities and moisture to ensure that the calorific value of the biogas meets the usage requirements.

[0030] When the electro-chemical reaction reaches the set time, turn off the power supply to stop the electrolysis reaction, and drain the treated wastewater from the electrolytic cell through a valve. Ensure that no secondary pollution is generated during the entire drainage process. The drainage pipeline should be reasonably designed to avoid blockage by sediment. Conduct water quality monitoring, including the detection of indicators such as COD, BOD, SS, and pH, to confirm that the treated wastewater meets the discharge standards or can be used for reuse. The monitoring results should be recorded to ensure compliance. After confirming that the water quality meets the standards, allow the treated wastewater to be discharged to the designated location or used for subsequent reuse processes; Install a gas collection device at the top of the UASB reactor to ensure that the biogas generated during the reaction can be effectively collected. According to the operating conditions of the reactor, regularly collect biogas and record the gas generation rate and total amount. Use a gas analyzer to monitor the composition of biogas (such as methane, carbon dioxide, hydrogen sulfide, etc.) to ensure that the methane content in the biogas meets the usage requirements. The biogas is passed through a gas purification device to remove impurities and moisture to improve its calorific value and combustion efficiency. The purified biogas can be directly used for power generation, heating, or as a raw material for bio-gas.

[0031] Post-treatment of wastewater; For the pollutants remaining after electro-chemical treatment, set up an aerobic treatment unit for further treatment. Start the aerobic reactor, set the influent flow rate and the concentration of cultivated sludge, introduce the purified biogas into the generator set for energy conversion, and the treated wastewater can be further used for irrigation and reuse.

[0032] After electro-chemical treatment, enter the aerobic treatment unit and start the aerobic reactor. According to the water quality and flow rate of the wastewater after electro-chemical treatment, set an appropriate influent flow rate. Ensure a stable flow rate to maintain good reaction conditions. According to the reactor design and sewage characteristics, add an appropriate concentration of activated sludge, usually in the range of 3000 - 6000 mg / L, to improve the removal rate of the remaining organic matter in the wastewater. Monitor parameters such as dissolved oxygen concentration, temperature, and pH in the aerobic reactor to ensure that the reaction conditions are suitable for the growth and metabolism of microorganisms to achieve the best decontamination effect. The purified biogas collected from the UASB reactor should be passed through a gas purification device to remove impurities to ensure that it is suitable for input into the generator set. Introduce the purified biogas into the generator set for energy conversion, use it for power generation or heating, and improve the overall energy utilization efficiency of the system. The wastewater after aerobic treatment can be further disinfected, such as chlorination, ultraviolet treatment, etc., to ensure that the water quality meets the irrigation or reuse standards.

[0033] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made in these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for treating UASB wastewater, characterized in that: The steps include: Wastewater pretreatment; Multi-stage UASB reactor treatment; Electrochemical oxidation treatment; Product collection and biogas recovery; Wastewater post-treatment.

2. The UASB wastewater treatment method according to claim 1, characterized in that: The wastewater pretreatment specifically includes: Collect wastewater: collect high-concentration organic wastewater and use raw material pump to transport the wastewater to the pretreatment tank; Physical screening: Install a screen at the entrance of the pretreatment tank to remove large particles in the wastewater, and set a grit chamber in the pretreatment tank to keep the grit time at 30 minutes to remove sediment; pH adjustment: Use a pH meter to detect the pH value of the wastewater. If the pH value is lower than 6.5, add lime water to increase it. If it is higher than 7.5, add dilute sulfuric acid to lower it, ensuring that the pH before entering the UASB reactor is between 6.5-7.

5.

3. The UASB wastewater treatment method according to claim 2, characterized in that: The multi-stage UASB reactor treatment specifically includes: Entering the first-stage UASB reactor: The pretreated wastewater is transported to the first-stage UASB reactor through a pipeline, and the flow rate is set to 0.5-1 m / h. Make sure that a mixing device is set in the reactor to ensure that the sewage and sludge are fully in contact. The residence time of the reactor is set to 12-24 hours, and the COD removal rate is continuously monitored. It can enter the next stage when it reaches more than 60%; Sludge circulation: A sludge return pump is installed at the bottom of the first-stage UASB reactor to regularly return the precipitated activated sludge to the top of the reactor. The return ratio is set at 30%-50% to improve the degradation efficiency of the activated sludge. Gas collection: Install a gas collection device on the top of the first-stage reactor to ensure that the generated biogas can be collected, and regularly monitor the gas composition and output to ensure effective anaerobic reaction; Entering the second-stage UASB reactor: The wastewater treated by the first-stage UASB reactor is introduced into the second-stage UASB reactor through the bottom pipe, with the flow rate maintained at 0.5 m / h and the residence time set at 12 hours to further remove undegraded organic matter; Continue sludge return: A sludge return mechanism is also set up in the second-stage UASB reactor to regularly return the precipitated sludge to the first-stage UASB reactor, monitor the sludge return volume, and ensure that the sludge concentration in the reactor is between 0.5-2 g / L.

4. The UASB wastewater treatment method according to claim 3, characterized in that: Before the wastewater enters the first-stage UASB reactor, a heat exchanger is used to preheat the wastewater to 30-35°C to increase the activity and degradation efficiency of anaerobic microorganisms.

5. The UASB wastewater treatment method according to claim 3, characterized in that: Multiple reaction sections are set in the first-stage UASB reactor. Each section has different sludge concentration and flow rate to form a gradient flow and promote the degradation of different organic matter. Each section is equipped with an independent sludge return system to adjust the return ratio of each section to adapt to different reaction conditions.

6. The UASB wastewater treatment method according to claim 3, characterized in that: Add biological additives in the first-stage UASB reactor to improve the degradation and sedimentation capacity of sludge. Regularly monitor the sludge activity and adjust the addition amount.

7. The UASB wastewater treatment method according to claim 1, characterized in that: The electrochemical oxidation treatment specifically comprises: Entering the electrochemical oxidation unit: The wastewater treated in the second-stage UASB reactor is transported to the electrochemical oxidation unit through a pipeline. Stainless steel electrodes are installed in the electrochemical oxidation unit to ensure that the electrode spacing is 5-10 cm to optimize the current density; Filling the electrolyzer: inject the UASB-treated wastewater into the electrolyzer to ensure that the water level reaches the minimum immersion depth of the electrodes; Apply current: Turn on the power supply, set the DC current to 20-50 mA / cm², ensure that the current is evenly distributed, monitor the voltage and current in the electrolytic cell to ensure that they are stable and avoid overload, conduct the electrolysis reaction for 2-4 hours, and take samples every 30 minutes for water quality analysis to ensure that the removal rate of organic matter reaches more than 70%.

8. The UASB wastewater treatment method according to claim 1, characterized in that: The product collection and biogas recovery specifically include: Wastewater discharge and monitoring: After the electrochemical reaction is completed, the treated wastewater is discharged from the electrolytic cell and the water quality is monitored. After confirming that the water quality meets the standards, it is discharged; Biogas collection: The gas collection device on the top of the UASB reactor collects biogas regularly, monitors the gas composition, and uses a gas purification device to remove impurities and moisture to ensure that the calorific value of the biogas meets the usage requirements.

9. The UASB wastewater treatment method according to claim 7, characterized in that: The wastewater post-treatment and resource recovery specifically include: For pollutants that still exist after electrochemical treatment, an aerobic treatment unit is set up for further treatment. The aerobic reactor is turned on, the water inlet flow rate and the culture sludge concentration are set, and the purified biogas is introduced into the generator set for energy conversion. The treated wastewater can be further used for irrigation and reuse.

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